What Is a Planet? - GLORIA DICKIE

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What Is a Planet? - GLORIA DICKIE
Polar Bears Hunt With Weapons | Ice Gets Bent Out of Shape

                     MAGAZINE OF THE SOCIETY FOR SCIENCE s AUGUST 28, 2021

     What Is
     a Planet?
       Fifteen years after
       Pluto lost its title,
       scientists still
       don’t agree

cover_pluto.indd 1                                                           8/11/21 1:42 PM
What Is a Planet? - GLORIA DICKIE
ON FIRE AND UNDER WATER
       SOLUTIONS FOR OUR BURNING PLANET AND ITS RISING OCEANS

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        sees that—or writes about it—better                                                     us of what we are capable of as
        than Stephen Pyne. This is a brilliant                                                individuals to improve the future of
             guidebook to that future.”          The essential guide to California’s long           our planet and people.”
         —David Wallace-Wells, author of          relationship with fire, updated for the               —Kirkus Reviews
              The Uninhabitable Earth                   climate-change generation.

         A history of our relationship—and                                                     “The book is carefully and clearly
          responsibilities—to our beaches                                                     written, demonstrating the author’s
               and their ecosystems.                                                        commitment to climate work . . . as well
                                                 “Manages to inspire both pragmatism          as the depth of her own knowledge
                                                   and optimism, which likely stems              as an environmentalist. Highly
                                                 from the immense number of people                      recommended.”
                                                   working . . . to better understand                      —CHOICE
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                                                                 —Forbes

                                                                                                www.ucpress.edu

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What Is a Planet? - GLORIA DICKIE
VOL. 200 | NO. 4

                                                                                                                                                                  Features
                                                                                                                                                                  20   Pluto’s Place
                                                                                                                                                                       COVER STORY Fifteen years after astronomers voted
                                                                                                                                                                       to redefine “planet,” some scientists say it’s time to
                                                                                                                                                                       revisit that definition. A look back shows the term’s
                                                                                                                                                                       meaning has been ever-changing. By Lisa Grossman

                                                                                                                                                                  24   The Debate Over
                                                                                                                                                                       Gender-Affirming Health Care
                                                                                                                                                                       As some states seek to limit transgender youths’
                                                                                                                                                                       access to gender-affirming health care, researchers
                                                                                                                                                                       are studying the mental health effects of age-
                                                                                         24
                                                                                                                                                                       appropriate care. By Maria Temming

                                                                                     News
                                                                                     6        Microscopic fossils push       10 The dino-killing asteroid 18 News in Brief
                                                                                              back the start of animal          unleashed a tsunami          An odd gamma-ray burst
                                                                                              life, a scientist contends        that may have left           may have been the death
                                                                                                                                giant ripple marks under     knell of a massive star
                                                                                     7        The moon’s magnetic field
                                                                                                                                Louisiana
                                                                                              lasted for just a blip in                                      The coronavirus razes
                                                                                              geologic time, a study hints   12 Viruses help moth            a crucial cell barrier to
                                                                                                                                                                                                    4
                                                                                     8        Sea level change can cause        caterpillars combat          cause severe COVID-19
                                                                                                                                killer parasites
                                                                                              a sea change in Santorini’s
                                                                                              volcanic activity              14 How speedy squirrels
                                                                                                                                                             Black holes born with
                                                                                                                                                             magnetic “hair” quickly
                                                                                                                                                                                               Departments
                                                                                              Colliding light might             jump from tree to tree       shed it, computer                  2        EDITOR’S NOTE
                                                                                              demonstrate Einstein’s            without falling              simulations suggest
                                                                                                                                                                                                4        NOTEBOOK
                                                                                              equation E=mc2                                                                                             Ice can bend without
                                                                                                                             16 For some polar bears,         To survive harsh winters,
   FROM TOP: DREW ANGERER/GETTY IMAGES; ALMA/ESO, NAOJ AND NRAO, M. BENISTY ET AL;

                                                                                     9        Pterosaurs may have               stone and ice may be the      pikas slow down their                      breaking; a baby exoplanet
                                                                                              taken to the air soon after       perfect tools for hunting     metabolism and snack on                    could be making moons
                                                                                              hatching                          walruses                      yak poop                          30 REVIEWS & PREVIEWS
                                                                                                                                                                                                   A new book tackles
   JOHN CAPINERA/UNIV. OF FLORIDA, BUGWOOD.ORG (CC BY-NC 3.0 US)

                                                                                                                                                                                                   pseudoscience; another
                                                                                                                                                                                                   looks at the Big Bang
                                                                                                                                                                                                   theory’s origins

                                                                                                                                                                                                34 FEEDBACK

                                                                                                                                                                                                36 SCIENCE VISUALIZED
                                                                                                                                                                                                   See how a glass sponge
                                                                                                                                                                                                   alters the flow of water

                                                                                                                                                                                                        COVER Pluto rises above
                                                                                                                                                                                                        the horizon of its largest
                                                                                                                                                                                                        moon, Charon, in this
                                                                                                                                                                                                        illustration. Mark Garlick/
                                                                                                                                                                                                        Science Photo Library/Getty
                                                                                         12                                                                                                             Images Plus

                                                                                                                                                                                         www.sciencenews.org | August 28, 2021 1

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What Is a Planet? - GLORIA DICKIE
EDITOR’S NOTE

                                           Debate over Pluto’s planet
                                                                                                                                         publisher Maya Ajmera
                                                                                                                                         editor in chief Nancy Shute

                                                                                                                                         editorial

                                           status still carries on                                                                       editor , special projects Elizabeth Quill
                                                                                                                                         news director Macon Morehouse
                                                                                                                                         digital director Kate Travis
                                                                                                                                         features editor Cori Vanchieri
                                     Fifteen years ago, Pluto was kicked out of the planet club.                                         managing editor , magazine Erin Wayman
                                                                                                                                         deputy news editor Emily DeMarco
                                     On August 24, 2006, members of the International                                                    associate news editor Ashley Yeager
                                                                                                                                         associate editor Cassie Martin
                                     Astronomical Union voted in favor of a new definition of                                            associate digital editor Helen Thompson
                                                                                                                                         audience engagement editor Mike Denison
                                     what constitutes a planet. What was once considered the                                             astronomy Lisa Grossman
                                     solar system’s ninth planet no longer qualified.                                                    behavioral sciences Bruce Bower
                                                                                                                                         biomedical Aimee Cunningham
                The public outcry was immediate. “In changing the definition of planet, the                                              earth and climate Carolyn Gramling
                                                                                                                                         life sciences Susan Milius
            International Astronomical Union is messing with something much bigger than                                                  molecular biology, senior writer Tina Hesman Saey
                                                                                                                                         neuroscience , senior writer Laura Sanders
            it is,” one Science News reader complained in a letter to the editor. “Think of all                                          physics , senior writer Emily Conover
                                                                                                                                         social sciences Sujata Gupta
            the dictionaries, encyclopedias, textbooks and websites that will need revision.”                                            staff writers Erin Garcia de Jesús, Jonathan Lambert
                                                                                                                                         editorial assistant Aina Abell
                Many planetary scientists were upset too, though mostly for other reasons. As                                            science writer interns Jaime Chambers, Nikk Ogasa
                                                                                                                                         contributing correspondents
            astronomy writer Lisa Grossman explains in this issue (Page 20), some research-                                              Laura Beil, Tom Siegfried, Alexandra Witze
            ers thought the new definition — that a planet is a spherical body that orbits the                                           design
                                                                                                                                         chief design officer Stephen Egts
            sun (which Pluto is) and has cleared other objects out of its orbit (which Pluto                                             design director Erin Otwell
                                                                                                                                         art director Tracee Tibbitts
            hasn’t) — was too restrictive. Some scientists still lobby for a broader definition.                                         assistant art director Chang Won Chang
                The debate over classifying solar system objects reminds me of another classifi-                                         science news for students
            cation challenge: categorizing the diversity of life on Earth. As a child, I remember                                        editor Janet Raloff
                                                                                                                                         managing editor Sarah Zielinski
            learning about the five kingdoms of life: animals, plants, fungi, protists (things                                           assistant editor Maria Temming
                                                                                                                                         web producer Lillian Steenblik Hwang
            like algae) and monerans (bacteria). Though there was never a vote (that I’m                                                 society for science
            aware of ), that system was superceded. In the 1990s, biologists proposed new                                                president and ceo Maya Ajmera
                                                                                                                                         chief of staff Rachel Goldman Alper
            groups such as domains — bacteria, archaea (unicellular organisms that had once                                              chief marketing officer Kathlene Collins
                                                                                                                                         chief program officer Michele Glidden
            been considered bacteria) and eukaryotes. More recently, scientists have debated                                             chief, events and operations Cait Goldberg
                                                                                                                                         chief communications officer Gayle Kansagor
            how to organize eukaryotes, organisms that store DNA within a cell nucleus. For                                              chief advancement officer Bruce B. Makous
                                                                                                                                         chief technology officer James C. Moore
            example, did you know you’re an opisthokont? According to some biologists, all                                               chief financial officer Dan Reznikov

            animals, fungi and some single-celled eukaryotes fall into that “supergroup”                                                 board of trustees
                                                                                                                                         chair Mary Sue Coleman
            (SN: 8/8/15, p. 22). The name, roughly meaning “rear pole,” references the fact                                              vice chair Martin Chalfie treasurer Hayley Bay Barna
                                                                                                                                         secretary Paul J. Maddon at large Christine Burton
            that many opisthokonts have at least some cells powered by a whiplike tail. Ani-                                             members Craig R. Barrett, Adam Bly, Mariette DiChristina,
                                                                                                                                         Tessa M. Hill, Tom Leighton, Alan Leshner, W.E. Moerner,
            mals, for instance, have sperm. But I doubt many schoolchildren would cry if we                                              Dianne K. Newman, Thomas F. Rosenbaum, Gideon Yu,
            lost our membership in this group, as they did over Pluto’s “demotion.”                                                      Feng Zhang, Maya Ajmera, ex officio
                                                                                                                                         advertising and subscriber services
                Categorizing life is an ongoing process, and even the definition of life itself                                          advertising Daryl Anderson
            is uncertain, with questions about whether viruses should be considered                                                      science news in high schools Anna Rhymes
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            alive. Still, classification is more than just semantics. These groupings serve a                                            Science News
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            ject to new information. As Grossman shows, the 2006 vote didn’t end debate                                                  Mail Science News, PO Box 292255, Kettering, OH
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            over what defines a planet. Some scientists now argue that interesting geol-                                                 Editorial/Letters: feedback@sciencenews.org
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            2 SCIENCE NEWS | August 28, 2021

ed note.indd 2                                                                                                                                                                                   8/11/21 2:15 PM
What Is a Planet? - GLORIA DICKIE
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_p3.indd 3                                                                                                                                      7/29/21 4:04 PM
What Is a Planet? - GLORIA DICKIE
NOTEBOOK

                                                  Some soil samples collected
                                                  near Shackleton Glacier in
            Excerpt from the                      Antarctica (shown) were
            August 28, 1971                       seemingly devoid of microbial
            issue of Science News                 life, an unexpected finding.

            50 YEARS AGO                        THE SCIENCE LIFE

            The shrinking                       Missing microbes hint at limits on the search for E.T.
            mass of Pluto                       Even in the harshest environments,                    though the air around Shackleton Glacier
            Pluto was the last of the plan-     microbes always seem to get by. They                  is so cold and so arid that he often left his
            ets to be discovered (in 1930).     thrive everywhere from boiling-hot                    damp laundry outside to freeze-dry.
            If astronomers continue to          seafloor hydrothermal vents to high on                   Surprisingly, some of the coldest,
            make it lighter, it may be the      Mount Everest. Clumps of microbial cells              driest soils didn’t seem to be inhabited
            first to disappear.… [The lat-      have even survived for years in outer space           by microbes at all, Fierer and colleagues
            est measurement] brings             (SN: 9/26/20, p. 10).                                 report in the June Journal of Geophysical
            Pluto down to 0.11 of Earth’s          There was no reason for microbial ecolo-           Research: Biogeosciences. To Fierer’s
            mass, less than an eighth of        gist Noah Fierer to expect that any of the            knowledge, this is the first time that sci-
            its former self.… The wide          204 soil samples he and colleagues had                entists have found soils that don’t appear
            discrepancies among the             collected near Antarctica’s Shackleton                to support any kind of microbial life.
            figures presented for the           Glacier would be different. A spoonful of                The findings suggest that exceedingly
            mass of Pluto illustrate the        typical soil could easily contain billions            cold and arid conditions might place a hard
            particular difficulties of mea-     of microbes, and Antarctic soils from                 limit on microbial habitability and raise
            suring its mass.… If a planet       other regions host at least a few thousand            questions about how negative scientific
            has satellites, its mass can be     per gram. Fierer assumed that all of his              results should be interpreted, especially in
            determined from studying            samples would host at least some life, even           the search for life on other planets. “The
            their motions.… But Pluto
            has no known satellites.
                                                                                  HOW BIZARRE
            UPDATE: The discovery of
            Pluto’s moon Charon in 1978
                                                                                  Ice gets flexible in lab experiments
            (SN: 7/15/78, p. 36) finally                                          Ice’s well-established reputation for being stiff and brittle may

                                                                                                                                                                                                           FROM TOP: ALMA/ESO, NAOJ AND NRAO, M. BENISTY ET AL; COURTESY OF N. FIERER
            allowed astronomers to ac-                                            be ruined. Thin, pristine threads of ice are bendy and elastic,
            curately calculate the planet’s                                       scientists report in the July 9 Science.
            mass: about 0.2 percent of                                               To create the flexible ice, nanoscientist Peizhen Xu of
            Earth’s mass. Decades after                                           Zhejiang University in Hangzhou, China, and colleagues used
            scientists resolved Pluto’s heft,     A tiny thread                   a needle with an electric voltage applied to it, which attracted
                                                  of ice (shown
            the planet received arguably          in a micro-                     water vapor within a chilled chamber. The resulting ice whis-
            the greatest demotion of              scope image)                    kers were a few micrometers in diameter or less. Ice usually
            all — a downgrade to dwarf            can bend into                   contains defects: tiny cracks, pores or misaligned sections of
                                                                                                                                                           FROM TOP: N. FIERER; P. XU ET AL/SCIENCE 2021

                                                  a curve and
            planet (SN: 9/2/06, p. 149).          spring back                     crystal. But the ice threads consisted of near-perfect crystals,
            Some astronomers have since           to its original                 giving the threads atypical properties. Between –70° and
            proposed alternate definitions        shape when                      –150° Celsius, scientists could curve the ice into a partial circle
                                                  released.
            for the term “planet” that, if                                        with a radius of tens of micrometers. When the team released
            widely adopted, would restore                                         the bending force, the fibers sprang back to their original
            Pluto to its former rank (see                                         shape. Bending the fibers compresses the ice on its inside
            Page 20).                                                             edge, inducing the ice to take on a different structure. That
                                                                                  discovery could give researchers a new way to study ice’s prop-
                                                                                  erties when squeezed. — Emily Conover

            4 SCIENCE NEWS | August 28, 2021                                                         Watch a video of ice bending at bit.ly/SN_IceSpring

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What Is a Planet? - GLORIA DICKIE
challenge comes back to this sort of         another method to try, he says.
                                                                                                                                      philosophical [question]: How do you            Polar microbiologist Jeff Bowman
                                                                                                                                      prove a negative?” says Fierer, of the       sees the findings as an indication that
                                                                                                                                      University of Colorado Boulder.              current technology can’t detect very
                                                                                                                                         Proving a negative result is notori-      low levels of life, which can lead to
                                                                                                                                      ously difficult. No measurement is           false-negative results. “Certainly, there
                                                                                                                                      perfectly sensitive, so there’s always a     were things there,” says Bowman, of the
                                                                                                                                      possibility that a well-executed experi-     Scripps Institution of Oceanography in
                                                                                                                                      ment will fail to detect something that is   La Jolla, Calif. “This is Earth. This is an
                                                                                                                                      actually there. It took nearly two years     environment that is massively contami-
                                                                                                                                      of experiments based on multiple meth-       nated with life.”
                                                                                                                                      ods before Fierer and his University of         Even if there were a few microbes in
                                                                                                                                      Colorado colleague Nick Dragone finally      the soil, that wouldn’t undermine the
                                                                                                                                      felt confident enough to announce that       team’s evidence that cold and aridity         PICTURE THIS
                                                                                                                                      they’d found seemingly microbe-free          pose a serious challenge to life, Dragone
                                                                                                                                      soils. And the scientists intentionally      says. “It’s the combination of multiple
                                                                                                                                                                                                                                 A forming exoplanet
                                                                                                                                      stated only that they were unable to         very challenging environmental condi-         could make moons
                                                                                                                                      detect life in their samples, not that the   tions that restricts life more than just
                                                                                                                                      soils were naturally devoid of life. “We     one acting by itself.”                          New telescope images may provide
                                                                                                                                      can’t say the soils are sterile. Nobody         As scientists search for evidence of         the first view of moons forming out-
                                                                                                                                      can say that,” Fierer says. There’s always   life beyond Earth, they will be forced          side the solar system.
                                                                                                                                                                                   to walk the line between evidence                  The Atacama Large Millimeter/
                                                                                                                                                              Microbe-free soil    of absence and absence of evidence.             submillimeter Array, or ALMA, in
                                                                                                                                                        samples raise questions    “What we’re trying to do on Mars is             Chile glimpsed a dusty disk of poten-
                                                                                                                                                         about how to interpret    kind of the reverse of what we’ve tried         tially moon-forming material around
                                                                                                                                                          negative results, says
                                                                                                                                                        researcher Noah Fierer.    to do on Earth,” says polar microbiolo-         a baby exoplanet about 370 light-
d                                                                                                                                                                                  gist Lyle Whyte of McGill University in         years from Earth. The Jupiter-like
                                                                                                                                                                                   Montreal. On Earth, claiming that an            world is surrounded by enough mate-
                                                                                                                                                                                   environment is lifeless is a tough scien-       rial to make up to 2.5 Earth moons,
n                                                                                                                                                                                  tific sell. On Mars, it will be the other       researchers report in the July 20
                                                                                                                                                                                   way around. — Elise Cutts                       Astrophysical Journal Letters.
                                                                                                                                                                                                                                      ALMA observed a planet dubbed
                                                                                                                                                                                                                                   PDS 70c circling the star PDS 70
                                                                                                                                      THE –EST                                                                                     (center, above) in July 2019. Unlike
                                                                                                                                                                                                                                   most known exoplanets, this world
                                                                                                                                      A skeleton unearthed in Peru vies for the title                                              is still forming, gobbling up material
y                                                                                                                                     of oldest known shark attack victim                                                          from the disk of gas and dust swirling
                                                         FROM TOP: ALMA/ESO, NAOJ AND NRAO, M. BENISTY ET AL; COURTESY OF N. FIERER

                                                                                                                                      When news broke in June that the oldest known case of a person killed by a shark             around its star. During this forma-
                                                                                                                                      involved a member of Japan’s Jōmon culture around 3,000 years ago (SN Online:                tion process, planets are expected to
                                                                                                                                      7/23/21), two researchers took special notice.                                               wrap themselves in their own debris
                                                                                                                                         Back in 1976, bioarchaeologist Robert Benfer of the University of Missouri in             disks, which control how planets
                                                                                                                                      Columbia and anthropological archaeologist Jeffrey Quilter of Harvard University             pack on material and form moons.
                                                                                                                                      helped excavate a roughly 17-year-old boy’s skeleton at a Peruvian village site                 Around PDS 70c, ALMA spotted
                                                                                                                                      called Paloma. The remains bore signs of a fatal shark encounter: One of the boy’s           a disk of dust (small dot, right of the
                                                                                                                                      legs was missing, and his hip and forearm bones displayed deep bite marks char-              star) about as wide as Earth’s orbit
    FROM TOP: N. FIERER; P. XU ET AL/SCIENCE 2021

                                                                                                                                      acteristic of those made by sharks. Radiocarbon dating indicated that the teen               around the sun. With previously
                                                                                                                                      died around 6,000 years ago, Benfer says. That could make the teen the real oldest           reported exomoon sightings still
e                                                                                                                                     known shark attack victim.                                                                   controversial (SN Online: 4/30/19),
                                                                                                                                         Quilter described the youth’s shark-related injuries in two paragraphs in the             the new observations offer some of
                                                                                                                                      1989 book Life and Death at Paloma. But the results were never published in an               the best evidence yet that planets
                                                                                                                                      academic journal. Quilter and Benfer e-mailed the excerpt to the Jōmon research-             orbiting other stars have moons.
                                                                                                                                      ers on July 26. “We were unaware of their claim until now but are keen to speak to           — Maria Temming
-                                                                                                                                     them about it in more detail,” says archaeologist J. Alyssa White of the University
                                                                                                                                      of Oxford, who led the Jōmon team. — Bruce Bower

g                                                                                                                                                                                                                                 www.sciencenews.org | August 28, 2021 5

                                                    notebook.indd 5                                                                                                                                                                                                    8/11/21 11:32 AM
What Is a Planet? - GLORIA DICKIE
News
                                                               LIFE & EVOLUTION

                                                               Oldest animal fossil claim stirs debate
                                                               Squiggly alleged sponge hints at a much earlier start for animals

             BY JAKE BUEHLER                                   the Cambrian Period, when an extreme            tubes in 1992 in rocks from Little Dal, an
             Pale, wormlike tubes in 890-million-              burst in the evolution of animal diversity      ancient reef system formed by cyano-
             year-old rock may be ancient sea sponges,         began (SN: 9/7/13, p. 12). Some other ani-      bacteria, in northwestern Canada’s
             a new study concludes. If confirmed, that         mals are known from nearly 20 million           Mackenzie Mountains. “I found this
             controversial claim would push back the           years earlier, but go too much further          thing that was totally out of place,” she
             origin of the earliest sponges by about           back in time and the fossils’ classifica-       says. “It was much more complex in
             350 million years and make the micro-             tion as animals becomes less certain            terms of its structure than anything that
             scopic squiggles the oldest known fossils         (SN: 4/4/15, p. 12). Based on genetic           could be made by cyanobacteria.”
             of animals.                                       data and sponges’ relative simplicity, the         She would have reported the curious
                Crucially, these fossils would imply           creatures are generally thought to have         squiggles then, but without much else
             that animals emerged in environmental             been the earliest form of animal life.          to tie the fossils to sponges besides a
             conditions previously thought unwork-                But some scientists aren’t convinced         general resemblance, Turner moved on.
             able for animal life, geologist Elizabeth         that the newly described tubes are              More than a decade later, other scientists
             Turner reports July 28 in Nature.                 sponge fossils. “Organisms from any-            published research showing that sponges
                Early in Earth’s history, the ocean            where on the tree of life can make wiggly,      preserved in rock could appear similar
             mostly lacked oxygen. It wasn’t until             little [branching and rejoining] struc-         to the pallid wiggles at Little Dal, so she
             about 800 million to 540 million years ago        tures,” says paleobiologist Jonathan            returned to her find.
             that a large pulse of the gas to the atmo-        Antcliffe of the University of Lausanne            Turner argues that many modern
             sphere, known as the Neoproterozoic               in Switzerland. The fossils lack features       sponges don’t have spicules. If ancient
             Oxidation Event, brought atmospheric              such as mineralized skeletal parts called       creatures were similar, the newly
             oxygen levels to within 10 to 50 percent          spicules that would identify the crea-          described fossils could be sponges. And
             of modern levels. That event boosted the          tures as sponges, he says.                      she suggests that sponges predating the
             amount of oxygen in surface ocean waters             What’s more, the finding doesn’t fit         Neoproterozoic Oxidation Event may
             (SN: 1/18/20, p. 7). Until that point, oxy-       with what scientists know about the             have scraped out an existence in “oxygen
             gen levels were thought to be too low to          availability of nutrients, biominerals          oases” along microbial reefs, living in
             sustain animal life. “But sponges are dif-        and oxygen in the whole ocean ecosystem         holes and reef flanks.
             ferent from other animals,” says Turner,          before the Cambrian Period, Antcliffe              It’s possible that early sponges
             of Laurentian University in Sudbury,              says. “Everything we know about the             emerged much earlier than the rest of
             Canada. “Some sponges in the modern               Earth’s oceans in this interval of time         animal life and remained in a kind of evo-
             world and in the rock record are known to         tells us that animals originated around         lutionary stasis in low-oxygen conditions,
             be tolerant of comparatively low oxygen           540 [million to] 550 million years ago.         Turner says. The evolution of more com-
             relative to modern ocean levels.”                 It’s a legion of evidence, and to overturn      plex animals would have had to wait until
                Until now, the earliest, unambigu-             such an enormously strong paradigm,             oxygen became more abundant.
             ous fossilized sponges date to about              you need more than ‘might be a sponge.’ ”          Scientists have known about odd types
             540 million years ago to the beginning of            Turner first found the network of            of fossils in the Little Dal reef for a while,
                                                                                                               says paleobiologist James Schiffbauer of
                                                                                                               the University of Missouri in Columbia.
                                                                                                               And previous genetic analyses have sug-
                                                                                                               gested that sponges evolved well before
                                                                                                               the Cambrian Period. “It has just been
                                                                                                               a matter of finding them if they were
                                                                                                               indeed preserved,” Schiffbauer says.
                                                                                                                  Future research could help confirm the
                                                                                                               fossils’ identity. Turner says she plans to
                                                                                                                                                                E.C. TURNER/NATURE 2021

                                                                                                               continue studying the ancient tubes, add-
                                                                                                               ing that more answers may come from
                     100 µm                                                            100 µm
                                                                                                               looking in the right places. “We need to be
             A skeletal fragment of a modern bath sponge (Spongia officinalis) has a characteristic branched   looking for similar material with a really
             structure. What’s claimed to be an ancient sponge fossil (inset) sports a similar structure.      open mind in rocks of similar age.” s

             6 SCIENCE NEWS | August 28, 2021

worm-fossil.indd 6                                                                                                                                        8/11/21 11:55 AM
What Is a Planet? - GLORIA DICKIE
ATOM & COSMOS

                                                     Lunar rocks hint at fleeting magnetism
                                                     The moon’s magnetic field lasted 500 million years at most

                                                     BY CAROLYN GRAMLING                            magnetic field for at least 4 b­illion years.
                                                     A lunar magnetic field may have                The magnetization of the bit of glass
                                                     p­ersisted for only a blip in geologic time,   happened due to the meteorite impact
                                                     a new study suggests.                          that also formed the glass itself, Tarduno
                                                        Shortly after the moon formed about         and colleagues suggest.                                                        1 mm
                                                     4.5 billion years ago, it may have begun          The idea that a meteorite impact can
                                                     generating a magnetic field, a protec-         produce strong magnetization in rocks             Lunar glass that formed in a meteorite strike
                                                                                                                                                      about 2 million years ago (example shown)
                                                     tive sheath that can deflect charged           has been discussed in previous scientific         probably was magnetized by the impact rather
                                                     particles from the sun. Now, analyses of       studies, Tarduno says. As a meteorite             than a magnetic field from the moon’s core.
                                                     moon rocks suggest that any lunar mag-         punches into the lunar surface at super-
                                                     netic field was gone by at least 4 billion     fast speeds, the impact can partially             lingered until as recently as 1 billion
                                                     years ago, researchers report August 4         ionize particles on the surface, creating         years ago (SN: 9/16/17, p. 10).
                                                     in S­cience Advances.                          thick, magnetized plasma. “The glass,                Geodynamicists have wrangled over
                                                        Magnetized lunar rocks brought back         as it was moving through this plasma,             how the moon’s small core could have
                                                     by Apollo astronauts decades ago were          acquired that strong magnetization,”              sustained a magnetic field for billions
                                                     the first indication that the moon may         he says.                                          of years or even if the moon ever had a
                                                     have once had an internal dynamo — in             The moon has been repeatedly bat-              magnetic field at all, says paleomagne-
                                                     which molten, iron-rich rock swirls            tered by meteorites over time (SN:                tist Lisa Tauxe of the Scripps Institution
                                                     inside the core of a celestial body, giv-      6/6/20, p. 32). Relatively young and              of Oceanography in La Jolla, Calif. Mod-
                                                     ing rise to a magnetic field (SN: 12/17/11,    highly magnetized lunar samples that              eling studies of the moon’s core “just
                                                     p. 17). But how long such a lunar dynamo       researchers have puzzled over may have            have a great deal of trouble generating
                                                     may have lasted has been unclear.              gotten their magnetization in the same            enough oomph to make a magnetic field,
                                                        The moon’s core is “really small,”          way the glass did, Tarduno says.                  whereas you can do that pretty easily
                                                     says geophysicist John Tarduno of the             If so, that may also help explain              for the Earth.” The new study, she says,
                                                     U­niversity of Rochester in New York.          results from recent s­tudies, based on            “presents a well-argued case against a
                                                     It’s not clear how that core could have        analyses of the magnetization of a moon           long-lived field.”
                                                     sustained a dynamo for long before cool-       rock dating to between 2.5 billion and               If any lunar magnetic field disap-
                                                     ing, he says.                                  1 billion years ago, that have suggested          peared about 4 billion years ago, the
                                                        Tarduno and colleagues examined the         the moon’s magnetic field might have              lengthy bombardment of the moon’s
                                                     magnetization of a handful of the Apollo                                                         surface by the solar wind since then
                                                     rock samples. Analyzing the magnetism          Earth’s moon has lacked a magnetic field,         may have left a hidden wealth of
                                                     of tiny shards of metal trapped in crys-       leaving it unprotected from the solar wind, for   helium-3 and water buried in the lunar
                                                                                                    at least 4 billion years, a study suggests.
                                                     tals in rock dating from 3.9 billion to                                                          soils (SN: 5/11/19 & 5/25/19, p. 8). Those
                                                     3.2 billion years ago showed that those                                                          are products that future moon expedi-
                                                     rocks were barely magnetized at all.                                                             tions may be able to mine for energy, as
                                                        But a piece of lunar glass that                                                               well as life support.
                                                     formed during a meteorite impact                                                                       Drilling into those soils may also
                                                     about 2 million years ago had a                                                                        give scientists an unprecedented
                                                     strong magnetic field, “just a lit-                                                                     glimpse at past physical properties
     FROM TOP: RORY COTTRELL; T. PESQUET/ESA, NASA

                                                     tle weaker than Earth’s today,”                                                                          of the sun, Tarduno says, which
                                                     Tarduno says. That’s odd,                                                                                 could also help scientists better
                                                     because “everyone agrees there                                                                             understand conditions on the
                                                     isn’t a magnetic field on the                                                                              early Earth (SN: 6/25/16, p. 12).
                                                     moon now, and there wasn’t                                                                                “[We] have the potential now to
                                                     one 2 million years ago,” he                                                                              learn both about the ancient sun
                                                     says. “How does this happen?”                                                                            and early Earth’s atmosphere,
                                                        Taken together, these findings                                                                       which you’re not going to get in
                                                     point to one conclusion, the team                                                                     any other way,” he says. “That’s really
                                                     says: The moon hasn’t generated a                                                                  exciting stuff.” s

                                                                                                                                                          www.sciencenews.org | August 28, 2021 7

moon.indd 7                                                                                                                                                                                      8/11/21 12:06 PM
What Is a Planet? - GLORIA DICKIE
NEWS

              EARTH & ENVIRONMENT                            the volcano to cave in, forming a lagoon                                                                                              e

              Sea level dips spur                            (SN: 3/10/12, p. 12).
                                                                To investigate how sea level might
                                                                                                                                                                                                   o
                                                                                                                                                                                                   v
              volcanic eruptions                             influence the volcano, physical geogra-
                                                             pher Christopher Satow and colleagues
                                                                                                                                                                                                   t
                                                                                                                                                                                                   p
              Santorini flare-ups are linked                 created a computer simulation of                                                                                                      S
              to periods of low sea level                    Santorini’s magma chamber, which sits                                                                                                 w
                                                             about four kilometers beneath the volca-                                                                                              u
              BY MARIA TEMMING                               no’s surface. When the sea level dropped
              When sea level drops far below the             at least 40 meters below the present-day                                                                                              a
              present-day level, the island volcano          level, the crust above the magma chamber                                                                                              o
              Santorini in Greece gets ready to rum-         splintered, the simulation showed. That                                                                                               a
              ble. A comparison of the activity of the       allows magma stored under the volcano        Sea level seems to influence eruptions from                                              s
                                                                                                          the partially submerged volcano of Santorini
              volcano with sea levels over the last          to “move up through these fractures and      (shown from above) in Greece. Lower sea lev-                                             o
              360,000 years suggests that when the sea       make its way to the surface,” says Satow,    els are historically linked to more eruptions.                                           I
              level dips more than 40 meters, it triggers    of Oxford Brookes University in England.                                                                                              s
              a fit of eruptions. During times of higher        Those magma-filled cracks should          and your hands’ inward pressure is the                                                   ly
              sea level, the volcano is quiet, researchers   take about 13,000 years to reach the sur-    weight of the ocean. As someone else                                                     v
              report in the August Nature Geoscience.        face and awaken the volcano, the team        pumps air into the balloon — like magma
                 Since more than half of the world’s         found. After the water rises again, the      building up under Earth’s crust — the                                                    le
              volcanic systems are in or near oceans,        cracks should take about 11,000 years to     pressure of your hands helps prevent the                                                 d
              sea levels probably similarly influence        close, stopping eruptions.                   balloon from popping. “As soon as you                                                    a
              other volcanoes, the researchers say.             It may seem counterintuitive that         start to release the pressure with your                                                  m
                 Santorini is a ring of islands surround-    lowering the amount of water atop the        hands, [like] taking the sea level down,                                                 t
              ing the central tip of a volcano poking        magma chamber would cause the crust to       the balloon starts to expand,” Satow says,                                               q
              out of the Aegean Sea. The entire vol-         splinter. Satow compares the scenario to     and ultimately the balloon breaks.                                                       v
              cano used to be above water, but a violent     wrapping your hands around an inflated         The team tested the simulation’s                                                       s
              eruption around 1600 B.C. caused part of       balloon, where the rubber is Earth’s crust   predictions by comparing Santorini’s                                                     le

              MATTER & ENERGY                                   Predicted more than 80 years ago,            Photons from a common source of                                                       B

              Light is caught                                the Breit-Wheeler process had never
                                                             been directly observed. New measure-
                                                                                                          light, such as a lightbulb or a laser, are
                                                                                                          considered real. But the bona fides of                                                   o
              making matter                                  ments from the STAR experiment at
                                                             Brookhaven National Laboratory in
                                                                                                          Brandenburg and colleagues’ photons are
                                                                                                          up for debate because the light the team
                                                                                                                                                                                                   W
                                                                                                                                                                                                   L
              But the result depends on                      New York match predictions for the elu-      collided came from an unusual source:                                                    O
              whether the photons are ‘real’                 sive transformation, physicist Daniel        the electromagnetic fields of two atomic                                                 a
                                                             Brandenburg and colleagues report in         nuclei that race around Brookhaven’s
              BY EMILY CONOVER                               the July 30 Physical Review Letters.         Relativistic Heavy Ion Collider.                                                         d
              Collide light with light, and poof, you get       “The idea that you can create mat-           Normally, photons from such elec-                                                     t
              matter and antimatter. It sounds like a        ter from light smashing together is an       tromagnetic fields are virtual. But in the
              simple idea, but it turns out to be sur-       interesting concept,” says Brandenburg,      experiment, the photons act as if they                                                   t
              prisingly hard to prove.                       of Brookhaven. It’s a striking demon-        are real due to the high speeds at which                                                 S
                A team of physicists is now claiming         stration of the physics immortalized         the two nuclei are zipping along. In cases                                               L
              the first direct observation of the long-      in E instein’s equation E=mc2, which         where the nuclei barely miss one another,                                                a
              sought Breit-Wheeler process, in which         revealed that energy and mass are two        their electromagnetic fields overlap and                                                 H
              two particles of light, or photons, crash      sides of the same coin.                      two photons from those fields can collide.                                               s
              into one another and produce an elec-             Whether the observation truly quali-      So the team looked for near-misses that
                                                                                                                                                            NASA EARTH OBSERVATORY

              tron and its antimatter counterpart, a         fies depends on whether the photons          spit out one electron and one positron.                                                  t
              positron. But the detection’s significance     are considered “real,” as demanded by           Measurements of angles between                                                        p
              hinges on whether the light is “real.”         the Breit-Wheeler process, or “virtual.”     those particles, which depend on                                                         t
                                                                                                                                                                                     MARK WITTON

              Some physicists argue the photons don’t        In particle physics, virtual particles are   whether real or virtual photons collided,                                                t
              qualify as real, raising questions about       ones that appear for only instants and       matched expectations for real photons,                                                   h
              the observation’s implications.                don’t carry their normal masses.             suggesting that the team had seen the                                                    li

              8 SCIENCE NEWS | August 28, 2021

volcano-fossil-light.indd 8                                                                                                                           8/11/21 12:08 PM
eruption history with geologic evidence       LIFE & EVOLUTION
                                          of past sea levels. All but three of the
                                          volcano’s 211 well-dated eruptions in         Newly hatched pterosaurs took flight
                                          the last 360,000 years happened during        A strong wing bone suggests the baby reptiles were agile fliers
                                          periods of low sea level, as predicted.
                                          Such periods of low sea level occurred        BY CAROLYN GRAMLING                                flight are strong bones, sufficient muscle
                                          when more of Earth’s water was locked         Pterosaur hatchlings may have been able            mass to stay in the air for a long time and
                                          up in glaciers during ice ages.               to fly right out of the shell. A new analysis      sturdy keratin fibers in the skin of the
                                             “It’s really intriguing and interesting,   of the fossilized wing bones of embryonic,         wings, analogous to bird feathers, Padian
                                          and perhaps not surprising, given that        newly hatched and adult pterosaurs sug-            says. “We know little about the last two.”
                                          other studies have shown that volcanoes       gests the baby creatures were strong and              Paleontologist Darren Naish of the
                                          are sensitive to changes in their stress      nimble fliers from the start, researchers          University of Southampton in England
                                          state,” says geophysicist Emilie Hooft        report July 22 in Scientific Reports.              and colleagues turned to bones, com-
                                          of the University of Oregon in Eugene.           Pterosaurs were a diverse group of              paring fossilized embryo and hatchling
                                          Icelandic volcanoes, for instance, have       flying reptiles that lived alongside dino-         wing measurements with those of adults
                                          shown an uptick in eruptions after over-      saurs from 228 million to 66 million               from two species: Pterodaustro guinazui
                                          lying glaciers have melted, relieving the     years ago during the Triassic and                  and Sinopterus dongi. The team zeroed
                                          volcanic systems of the weight of the ice.    Cretaceous periods. The group includes             in on one wing bone, the humerus, that
                                             As for Santorini, the last time sea        Quetzalcoatlus northropi, the larg-                offers key information on whether a
                                          level was 40 meters below the present-        est creature known to take wing, and               pterosaur was capable of getting off the
                                          day level was near the end of the last ice    Kunpengopterus antipollicatus, which               ground.
                                          age — and sea level is rising due to cli-     had opposable thumbs that enabled it to               Relative to hatchlings’ size, their
                                          mate change — so Satow’s team expects         climb trees (SN: 5/8/21 & 5/22/21, p. 16).         humerus bones were stronger than those
                                          the volcano to enter a period of relative        Scientists know relatively little about         of many of the adults, and hatchlings also
                                          quiet. But two major eruptions in the         whether young pterosaurs could actively            had shorter, broader wings, suggesting
                                          volcano’s history did happen amid high        flap their wings or only glide — which             that youngsters might have been capable
                                          sea levels, the team says, so future vio-     might mean they stayed under paren-                of nimbly changing direction and speed,
                                          lent eruptions aren’t off the table. s        tal care until they were flight-ready. But         and possibly flying long distances. Agile
                                                                                        relatively recent revelations increasingly         flying may have helped the hatchlings
                                                                                        point toward early independence, or pre-           escape predators and chase tricky prey
                                          Breit-Wheeler process.                        cociality, for the reptiles. For instance,         such as insects, all while navigating
                                             Strictly speaking, the experiment is       researchers have found flight mem-                 dense vegetation, the team suggests.
                                          one step removed from the true Breit-         branes on the wings of an embryonic                   It isn’t unusual in the animal world
                                          Wheeler process, says particle physicist      pterosaur and the remains of a juvenile            for young to fend for themselves, Padian
                                          Lucian Harland-Lang of the University of      that was capable of long-distance flying           says. “Precociality is the rule, not the
                                          Oxford. While the photons behave almost       long before it had grown to adult size.            exception, in vertebrates,” he says.
                                          as if real, they are technically virtual.        “Baby pterosaurs almost certainly               Only animals with extended parental
                                             Brandenburg and colleagues take a          didn’t glide,” they flew, says paleontolo-         care, such as songbirds and primates,
                                          different view, in which the reality of       gist Kevin Padian of the University of             can afford to be helpless for prolonged
                                          the photon is based on how it behaves.        California, Berkeley. The three keys to            periods. s
                                             The scientists’ measurements back
                                          that up, says laser plasma physicist          A flamingo-like pterosaur, Pterodaustro guinazui
                                          S tuart Mangles of Imperial College           (shown in this artist’s rendition), could fly
                                                                                        from the moment it emerged from its shell,
                                          London. “Everything they’re measuring         new research suggests.
                                          about it makes it look like a real photon.”
                                          However, Mangles says, the photons are
                                          still virtual by some definitions.
                                             Mangles and others are working
NASA EARTH OBSERVATORY

                                          toward detecting the Breit-Wheeler
                                          process with lasers, which produce light
                                          that’s as real as the light allowing you
                            MARK WITTON

                                          to read this article. That, physicists are
                                          hoping, will clinch the case for colliding
                                          light making matter. s

                                                                                                                                            www.sciencenews.org | August 28, 2021 9

                         volcano-fossil-light.indd 9                                                                                                                             8/11/21 12:09 PM
NEWS

                                                                                                          When the Chicxulub asteroid (illustrated)
                                                                                                          slammed into Earth millions of years ago, the
                                                                                                          impact formed a tsunami that may have left
                                                                                                          ripples in rock under present-day Louisiana.

                                                                                                          there should be a tsunami.”
                                                                                                             The ripple marks were preserved all
                                                                                                          this time thanks to the depth at which
                                                                                                          they formed underwater, Kinsland says.
                                                                                                          Other studies suggest that this region
                                                                                                          was 60 meters below the sea surface at
                                                                                                          the time. At that depth, the ripples would
                                                                                                          have been beyond the reach of tumultu-
             EARTH & ENVIRONMENT                                                                          ous storms that could have erased them.

             Dino-killing asteroid had a ripple effect                                                    Then, over millions of years, other sedi-
                                                                                                          ments slowly buried the marks.
             An impact-induced tsunami may have left behind giant ridges                                     A smaller, analogous set of struc-
                                                                                                          tures may exist off the east coast of
             BY NIKK OGASA                               which was underwater at the time                 Japan. There, a repeating sequence of
             The asteroid impact that slew the dino-     (SN: 11/25/17, p. 14). But no one had ever       underwater dunes was reported to have
             saurs may have also indirectly sculpted     before found ripple marks formed by the          appeared after the 2011 Tohoku earth-
             the largest ripple marks ever found on      sprawling wave.                                  quake and tsunami (SN: 2/25/12, p. 22).
             Earth.                                         Geologist Kaare Egedahl discovered            Except for the dunes’ size, they look
               A series of ridgelike structures more     the ripples while searching for coal             nearly identical to the ripple marks
             than three stories high and spaced          deposits. Studying at the University             buried beneath L ouisiana, K insland
             nearly two Eiffel Towers apart appear       of Louisiana at Lafayette at the time,           says. That supports the idea that the
             to be buried about 1.5 kilometers           E gedahl had been combing through                taller structures were also produced by
             beneath central Louisiana. The over-        seismic reflection data — 3-D images of          a tsunami, though one of a much larger
             sized features are megaripples shaped       buried rock and soil that were generated         magnitude.
             by a massive tsunami generated by the       by underground sound waves — provided               Still, there is contention over whether
             Chicxulub asteroid impact, researchers      by the Devon Energy company. Egedahl,            the features beneath Louisiana really are
             argue in the Sept. 15 Earth and Planetary   now at the oil and gas company Cantium           megaripples formed by the Chicxulub-
             Science Letters.                            in Covington, La., found the ripples atop        induced tsunami.
               “It’s just interesting that something     a layer of rock thought to have formed              “It’s hard to see how such a high-
             that happened 66 million years ago could    from debris shaken up by the Chicxulub           energy event could form ripple marks
             be so well preserved, buried 5,000 feet     asteroid impact. He then shared his find-        because they are usually associated
             down in the sediments of Louisiana,”        ing with Kinsland.                               with much calmer environments,” says

                                                                                                                                                                FROM TOP: MARK GARLICK/SCIENCE PHOTO LIBRARY/GETTY IMAGES; MARTELL STRONG
             says geologist Gary Kinsland of the            “I knew where that layer was from             sedimentologist Pedro J.M. Costa of
             University of Louisiana at Lafayette.       in geologic time, and I knew what hap-           the University of Coimbra in Portugal.
               Ripple marks are repeating sequences      pened there,” Kinsland says. “I knew             And ripple marks typically form from
             of ridges typically found on sandy                                                           frequent and recurring wave motion,
             beaches or stream bottoms and form          These are the ripples (most pronounced near      while tsunamis don’t have many waves,
             as wind or water flows over and moves       the red line in this reconstruction) beneath     he explains. Costa, who studies tsunami
                                                         Louisiana that a group of geologists say were
             loose sediment. But ripple marks on the     created by an asteroid-induced tsunami.          deposits, says that reconstructing the lay
             beach are often centimeters in height,                                                       of the seafloor at the time of the impact
                                                                                m
             while the structures found by Kinsland’s                     11.3 k                          and conducting experiments in water-
             team have an average height of 16 meters                                                     filled wave tanks could help unravel
             and are spaced about 600 meters apart.                                                       the origins of the structures found by
               The structures’ shape, size, ori-                                                          Kinsland’s team.
                                                                                                   17.7

             entation and location suggest that                                                              This new work is important because
                                                                                                     km

             they formed after the Chicxulub                                                              it opens a discussion, Costa says. Maybe
             asteroid crashed into the Yucatán                                                            the Chicxulub impact “was such a high-
             Peninsula in Mexico, generating a tsu-                                                       magnitude event that what we see in
             nami that washed across the Gulf of                                                          normal tsunami events don’t apply to
             Mexico and what is now Louisiana,                                                            this one.” s

             10 SCIENCE NEWS | August 28, 2021

ripples.indd 10                                                                                                                                           8/11/21 11:57 AM
STEM
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               IS
               WHERE STUDENTS LIKE YOU
               BEGIN TO CHANGE THE WORLD.
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_p11.indd 11                                                                                       7/29/21 4:07 PM
NEWS

              LIFE & EVOLUTION                                   insect virologist Madoka Nakai of             the instructions from another host

              Sick caterpillars                                  Tokyo U­niversity of Agriculture and
                                                                 T­echnology. A parasitoid wasp would kill
                                                                                                               remains unclear, he says.
                                                                                                                  Researchers discovered in the 1970s
              keep wasps at bay                                  a host that the virus needs to survive, so
                                                                 the virus fights for its home. “It’s very
                                                                                                               that virus-infected caterpillars could
                                                                                                               kill parasitoid wasp larvae using an
              Viruses stop young moths                           clever,” Nakai says.                          unknown viral protein. In the new study,
              from becoming wasp nurseries                          What’s more, some moth caterpillars        Herrero, Nakai and colleagues identi-
                                                                 make the wasp-killing proteins them-          fied PKF as wasp-killing proteins. The
              BY ERIN GARCIA DE JESÚS                            selves, the team found. It’s possible that    team infected moth caterpillars with
              When parasitic wasps come calling,                 in the distant past, a few moths survived a   one of three insect viruses that carry
              some caterpillars have a surprising ally:          viral infection and “got some presents” in    the genetic blueprints to make the
              a viral infection.                                 the form of genetic instructions for how      proteins. Then the researchers either
                 Insects called parasitoid wasps lay             to make the proteins, says insect pathol-     allowed wasps to lay their eggs in the
              their eggs inside young moth larvae,               ogist and geneticist Salvador Herrero         caterpillars or exposed wasp larvae to
              turning the caterpillars into unwitting,           of the U­niversity of Valencia in Spain.      hemolymph — the insect equivalent of
              destined-to-die incubators for possibly            Those insects could have then passed          blood — from infected caterpillars.
              hundreds of wasp offspring. That’s bad             the ability on to offspring. In this case,       Virus-infected caterpillars were poor
              news for viruses trying to use the cat-            “what doesn’t kill you makes you stron-       hosts of the parasitoid wasp Cotesia
              erpillars as replication factories. Viral          ger,” Herrero says.                           k­ariyai. Most young wasps died before
              infections can be lethal for the caterpil-            Previous studies had shown that            they had the chance to emerge from the
              lars, but their chances of surviving with          viruses and insects, including moths,         caterpillars into the world. Hemolymph
              a virus are probably higher than if wasps          can swap genes with each other. The new       from infected caterpillars was also an
              use them as a living nursery.                      finding is one of the latest examples of      efficient killer of wasp larvae, typically
                 Now, a study shows how certain                  this activity, says entomologist Michael      destroying more than 90 percent of
              viruses can help caterpillars stymie               Strand of the University of Georgia in        o­ffspring.
              parasitoid wasps. A group of proteins              Athens who was not involved in the               C. kariyai wasp larvae also didn’t
              dubbed parasitoid killing factor, or PKF,          research.                                     survive in caterpillars, including the
              that is found in some insect viruses are              “Parasite-host relationships are very      beet armyworm (Spodoptera exigua),
              incredibly toxic to young parasitoid               specialized,” Strand says. “Factors like      that make their own PKF. When the
              wasps, researchers report in the July 30           [PKF] are probably important in defin-        researchers blocked the genes for the
              Science.                                           ing which hosts can be used by which          proteins in these caterpillars, the wasps
                 The finding shows that viruses and              parasites.” But whether caterpillars stole    lived, a sign that the proteins are key for
              caterpillars can come together to                  the genetic instructions for the proteins     the caterpillars’ defenses.
              fight off a common wasp enemy, says                from viruses or viruses o­riginally stole        Some parasitoid wasps, including
                                                                                                               Meteorus pulchricornis, weren’t affected
              Some moth caterpillars, such as beet armyworms (one                                              by PKF from the viruses or the beet army-
              shown), possess viral proteins that kill the larvae of                                           worms, allowing the wasp offspring to
              p­arasitoid wasps incubating inside them, a study finds.                                         thrive inside caterpillars. That finding
                                                                                                               suggests that the wasp-fighting ability is
                                                                                                               species specific, says Elisabeth Herniou,

                                                                                                                                                             JOHN CAPINERA/UNIV. OF FLORIDA, BUGWOOD.ORG (CC BY-NC 3.0 US)
                                                                                                               an insect virologist at CNRS and the
                                                                                                               U­niversity of Tours in France who was
                                                                                                               not involved in the work. Pinpointing
                                                                                                               why some wasps aren’t susceptible could
                                                                                                               reveal the details of a long-held evolu-
                                                                                                               tionary battle between all three types of
                                                                                                               organisms.
                                                                                                                  The study highlights that “single
                                                                                                               genes can interfere with the outcome
                                                                                                               of [these] interactions,” Herniou says.
                                                                                                               “One virus may have this gene and the
                                                                                                               other virus doesn’t have it,” and that can
                                                                                                               change what happens when virus, cater-
                                                                                                               pillar and parasitoid all collide. s

              12 SCIENCE NEWS | August 28, 2021

caterpillar.indd 12                                                                                                                                    8/11/21 11:58 AM
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_p13.indd 13                                                                              8/11/21 1:58 PM
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                                                                                                          decisions, the researchers found some-
                                                                                                          thing interesting: Branch flexibility had
                                                                                                          about six times as great an influence on
                                                                                                          when squirrels decided to jump as did
                                                                                                          the length of the gap. If squirrels had
                                                                                                          cared more about distance, they would
                                                                                                          have jumped from about the same spot
                                                                                                          on the rod, regardless of its give.
                                                                                                             “We were surprised to see squirrels
                                                                                                          weighing both of these things simul-
                                                                                         As they jump,
                                                                                          fox squirrels   taneously, but in different amounts,”
                                                                                           make quick     Hunt says.
                                                                                        calculations to      The researchers upped the ante for five
                                                                                   balance trade-offs
                                                                                   between tree limb      squirrels by increasing the flexibility of
                                                                              flexibility and distance    branches as well as gap distance. Initial
                                                                                       between limbs.     leaps were less than graceful. No squirrels
                                                                                                          fell, but most had clunky landings at first,
             LIFE & EVOLUTION                             environments to navigate,” says Hunt,           grasping the peg they leaped to with their

             Leaping squirrels                            an integrative biologist at the University
                                                          of Nebraska Omaha.
                                                                                                          front paws and swinging around to pull
                                                                                                          themselves up instead of landing neatly
             use parkour tricks                              When jumping between bendy
                                                          branches, a squirrel must assess how far
                                                                                                          on all fours. But within five trials, “squir-
                                                                                                          rels learned to compensate for their
             Obstacle course reveals how                  it has to jump and know when to leap as         initial error,” Hunt says, which they did
             the animals navigate jumps                   it moves along a branch. Jump too early         by modifying their initial velocity.
                                                          and the squirrel will fall short. Too late,        If squirrels regularly encounter the
             BY JONATHAN LAMBERT                          and the squirrel will find itself out on a      same branches, such quick learning
             Parkour enthusiasts need look no fur-        part of the branch too flimsy from which        “might explain how they move so fluidly
             ther than up in the trees for inspiration.   to launch. Hunt wondered, “How are              and rapidly” across particular branches,
             Squirrels’ aerial acrobatics make the        they sensitive to that trade-off, manag-        Hunt explains. The rodents might be
             rodents masters of the form.                 ing to make accurate leaps?”                    such quick navigators, he says, because
                A detailed look at how squirrels navi-       To find out, he and colleagues               “they’ve already learned what they need
             gate narrow branches that bend and           designed an artificial forest obstacle          to know about that branch.”
             sway with the wind — where the smallest      course on the outskirts of the University          The squirrels surprised the research-
             error could spell death — shows that the     of California, Berkeley campus. Then the        ers in other ways too. For longer jumps,
             rodents make split-second calculations       team used peanuts to coax free-ranging          or those that necessitated landing higher
             to balance trade-offs between branch         fox squirrels (Sciurus niger) into run-         or lower than the starting point, many
             bendiness and the distance between tree      ning and jumping through a series of            squirrels rotated midair, using their legs
             limbs. And for particularly tricky jumps,    acrobatic tests.                                to “jump” off an adjacent vertical wall in
             squirrels improvise parkour-style moves         First, the unwitting subjects learned        a parkour-style maneuver. More often
             to stick the landing, researchers report     to leap from artificial branches of high,       than not, squirrels employed parkour
             in the Aug. 6 Science.                       medium or low stiffness across a gap to         to slow down if they were coming in too
                This research is “a great example         reach a prize: a peanut at the end of a         hot to a landing. “It’s an additional point
             of how cool ‘normal’ animals can be          landing peg. High-speed video captured          of control,” Hunt says.
             in their biomechanics,” says Michelle        details of the jumps, from launch point            For many arboreal animals, “jumping
             Graham, a biomechanist at Virginia Tech      to landing accuracy, for 12 squirrels           between limbs is such a common thing,
             in Blacksburg who was not involved with      spanning 96 leaping trials.                     and yet we so frequently only study it in
             the work. “We’ve all seen squirrels do          Unsurprisingly, the squirrels leaped         pieces,” Graham says, such as looking
             crazy stuff in nature, but no one ever       from more bendy branches earlier —              just at the launch but not the landing.
             pays any attention to it.”                   presumably to maximize jumping                  This study’s holistic look reveals “some-
                                                                                                                                                            JUDY JINN/UC BERKELEY

                That is unless you’re like Nathaniel      force — even though that increased the          thing really interesting about squirrels,
             Hunt, who has been mesmerized by             distance that the animals must clear,           that they take greater account of [branch
             watching squirrels flash through the         Hunt says. By comparing what the                bendiness] than the gap distance,” she
             overstory since graduate school. “Tree       squirrels actually did with statistical         notes. “I don’t know that I would’ve
             canopies are incredibly challenging          models that simulated optimal jumping           guessed that.” s

             14 SCIENCE NEWS | August 28, 2021                                     Watch squirrels leap through an obstacle course at bit.ly/SN_Squirrels

squirrel.indd 14                                                                                                                                      8/11/21 11:59 AM
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