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THE
PLANETARY
REPORT
JUNE
SOLSTICE 2019
VOLUME 39, NUMBER 2
planetary.org
SMALL-BODY
RENDEZVOUS
JAGGED LITTLE WORLDS
HOLD CLUES TO EARTH’S ORIGINS
BUT YIELD NEW PUZZLES
DEFENDING EARTH C SAMPLING AN ASTEROID C ADVOCATING FOR SPACE
SPACE ON EARTH
Precise Movements
Earth-Bound Tracking Devices Help Manage Spacecraft
DEEP-SPACE EXPLORATION by robotic space- maintenance and installation on pump and
craft requires the support of thousands of oil-flow fittings. The hydrostatic bearing liter-
workers back on Earth in facilities around ally floats the moving structure of the antenna,
the world. Canberra, Australia hosts one of which weighs about 4 million kilograms (8
NASA’s 3 Deep Space Network (DSN) stations, million pounds), on a film of oil only 0.1 mil-
operated by the Commonwealth Scientific and limeter (4 thousandths of an inch) thick, per-
Industrial Research Organisation (CSIRO). Each mitting the gigantic antenna to smoothly track
DSN station hosts one 70-meter and multiple spacecraft as Earth rotates.
34-meter dishes that receive data from space-
craft across the solar system. Here, mechanical “Space on Earth” seeks to highlight all kinds
engineer Rachel Twomey (apprentice), servo of ground-based facilities worldwide that
systems engineer Paul Richter, and mechanical are involved in planetary exploration. If
engineer Clayton Locke discuss maintenance you’d like to make a suggestion for a facility
on the hydrostatic azimuth bearing on the to feature in “Space on Earth,” please
CSIRO
70-meter antenna. The team is performing email planetaryreport@planetary.org.
2 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019
SNAPSHOTS FROM SPACE Contents
JUNE SOLSTICE 2019
12 Apollo 11 Little West
Crater Panorama
Mike Constantine looks back at
humans’ first landing on the Moon.
14 Rosetta’s Ancient Comet
Martin Rubin and Cecilia
Tubiana report some of the
fascinating science returned
by ESA’s flagship mission.
19
19 Treasure Hunting
With Hayabusa2
Makoto Yoshikawa and Elizabeth
Tasker explain the unexpected
challenges of Hayabusa2’s
multiple asteroid landings.
DEPARTMENTS
2 Space on Earth
We highlight the human
workers who make robotic
space missions succeed.
3 Snapshots From Space
Emily Lakdawalla admires a new
view of Jupiter’s swirling storms.
4 Your Place in Space
Bill Nye invites us to help defend
the planet from a huge rock.
5 Your Impact
The first of two new columns rounds
up all the ways Society members
are making a difference for space.
JUNO CAPTURED a swirling region of bright clouds in the wake of a
cyclonic storm as it dove toward its 18th close encounter with Jupiter on 12 8 Get Involved
February 2019. At left is the turbulent, blue-tinted pole; at right, the polar Do you want to participate in
clouds give way to the pinker belts and zones of Jupiter’s midlatitudes. space exploration? Get involved
The Juno team posts their images in raw, relatively unprocessed form on with The Planetary Society!
NASA/SwRI/MSSS/Gerald Eichstädt/Seán Doran
the web as soon as they land on Earth—and wait for members of the public
10 What’s Up?
to process them. This image is the result of an automated processing
Bruce Betts looks forward
pipeline developed by Gerald Eichstädt of Germany, followed by further to solar and lunar eclipses
enhancement by Seán Doran of Ireland. plus a meteor shower.
—Emily Stewart Lakdawalla
10 Where We Are
Emily Lakdawalla brings us
SEE MORE AMATEUR-PROCESSED SPACE IMAGES PLANETARY.ORG/AMATEUR
up to date with all the robots
SEE MORE EVERY DAY! PLANETARY.ORG/BLOGS traveling beyond Earth.
YOUR PLACE IN SPACE
BILL NYE is chief executive
officer of The Planetary Society.
BILL NYE
Chief Executive Officer
JENNIFER VAUGHN
Chief Operating Officer
COFOUNDERS
CARL SAGAN
1934–1996
Space Defense for Us All
BRUCE MURRAY
1931–2013
LOUIS D. FRIEDMAN
Executive Director Emeritus
BOARD OF DIRECTORS
Chairman of the Board
Your Membership Dollars at Work to Save the Planet
DANIEL T. GERACI
Managing Partner & Director,
Cygnus Investment Partners, Inc.
President
JAMES BELL LIFE IS UNCERTAIN, but you can be sure of this: idea for a spacecraft so massive that its gravity
Professor, School of Earth
and Space Exploration, Earth will be hit by a huge rock some day—or could act like a tow rope, pulling the potential
Arizona State University
Vice President
night. The chance is 100 percent. The thing we impactor aside. The kinetic impactor concept
HEIDI HAMMEL
Executive Vice President, don’t know is when. It could happen tomorrow, would slam one or more spacecraft into a dan-
or it could be 2,356 years from this afternoon, gerous asteroid to alter its course. You might
Association of Universities for
Research in Astronomy
Secretary
C. WALLACE HOOSER
but it will happen. If you’re a member, you are think a nuclear weapon would do the trick.
Associate Professor of Radiology,
University of Texas
doing something about it. Thank you. It might, but it might cause other problems.
Southwestern Medical School
Looking for a typical asteroid is like looking Blasting an object in deep space far enough in
Treasurer
LON LEVIN for a typical charcoal briquette…in the dark. I advance to deflect it might turn it into inter-
President and CEO,
GEOshare LLC mean the absolute pitch-black, sooty-jet, tar-pit planetary buckshot, which would hit Earth
dark. However, dark as they are, asteroids just as hard as the original unshattered object
BETHANY EHLMANN
Professor, California Institute of
Technology; Research Scientist,
Jet Propulsion Laboratory glow in the infrared because they’re warmer would have, only more spread out. Ouch.
JOHN LOGSDON
Professor Emeritus, Space
than space. They’re at about 150 Kelvins (150 I hope you’re familiar with the Laser Bees idea.
Policy Institute, The George
Washington University degrees Celsius above absolute zero or minus We supported some early lab research at the Uni-
ROBERT PICARDO 190 degrees Fahrenheit). That’s why we at The versity of Strathclyde in Scotland. The idea is that
Actor
BRITNEY SCHMIDT Planetary Society provide our Gene Shoemaker we’d build spacecraft outfitted with lasers driven
Near-Earth Object grants to amateur astrono- by solar panels. We’d concentrate laser beams
Assistant Professor,
School of Earth and
Atmospheric Sciences,
Georgia Institute of Technology mers who keep a lookout, and we advocate onto a promising area of an asteroid. The ablating
BIJAL “BEE” THAKORE
Regional Coordinator for Asia Pacific,
strongly to ensure governments continue to (burning off ) material would have momentum,
Space Generation Advisory Council
invest in more observations and more space which would nudge the asteroid onto an ever-so-
FILLMORE WOOD
Vice President and Regional Counsel, missions to near-Earth asteroids and comets. slightly different course. As an engineer, this is
BP, retired
ADVISORY COUNCIL Thanks again for your support. my favorite plan.
Let’s say we found an asteroid headed for In any scheme, the key is early detection. A
BUZZ ALDRIN
ROBERT D. BRAUN
DAVID BRIN
G. SCOTT HUBBARD us, crossing Earth’s orbit on a collision course. timely nudge could save us all. I cannot help
GARRY E. HUNT
BRUCE JAKOSKY What would we do about it? We have to think but recall the last line in the movie The Thing
RYAN JOHNSON
CHARLES E. KOHLHASE JR. about a hands-free course correction—a gentle From Another World. The journalist warns us:
BEN LAMM
LAURIE LESHIN
JON LOMBERG
tug or nudge from a spacecraft just big enough “Keep looking. Keep watching the sky.”
ROSALY LOPES
BOB MCDONALD
to ensure the object crosses our orbit when
PETE SLOSBERG
TIM SPAHR we’re not there.
Several far-out but reasonable schemes
DIPAK SRINIVASAN
KEVIN STUBE
LORNE TROTTIER
NEIL DeGRASSE TYSON have been proposed. The gravity tractor is an
CONTACT US: The Planetary Society, ON THE COVER: Comet Churyumov-Gerasimenko’s surface has been ravaged by close passages around the Sun.
60 South Los Robles Avenue, Pasadena, CA Pits mark the sources of dusty comet jets, and scalloped cliffs have receded and collapsed to generate dusty ponds of
91101-2016; General calls: 626-793-5100; comet material. Bluer areas in this false-color image hint at the presence of frozen water and other volatile compounds.
Email: tps@planetary.org; Internet: Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; Jacint Roger C The Planetary
planetary.org; Editor EMILY LAKDAWALLA; Report (ISSN 0736-3680) is published quarterly at the editorial offices of The Planetary Society, 60 South Los Robles
Art Director LOREN A. ROBERTS Avenue, Pasadena, CA 91101-2016, 626-793-5100. It is available to members of The Planetary Society. Annual dues
for HEARKEN CREATIVE; are $50 (U.S. dollars) for members in the United States as well as in Canada and other countries. Printed in USA. Third-
Copy Editors NICOLE YUGOVICH, class postage at Pasadena, California and at an additional mailing office. Canada Post Agreement Number 87424. C
KELLY BEATTY, and JASON DAVIS; Viewpoints expressed in articles and editorials are those of the authors and do not necessarily represent positions of
Technical Editor JAMES D. BURKE; The Planetary Society, its officers, or its advisers. © 2019 by The Planetary Society. All Rights Reserved. The Planetary
Science Editor BRUCE BETTS Society and The Planetary Report: Registered Trademarks ® The Planetary Society. Planetfest™ The Planetary Society.
4 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019
More on each story can be found online! Use the link provided.
YOUR IMPACT
You’re a Planetary Defender New Planetary
Mission
Webpages
Helping Observers WE’RE EXPLORING more!
Search the Skies Planetary exploration has
PLANETARY SOCIETY members play a direct kept a brisk pace over the
role in planetary defense through the Shoemaker past several years. To keep
Near-Earth Object Grant program. The grant members up to date, we
program supports highly skilled amateur have created new webpages
astronomers from around the world who track tracking missions, including
and characterize near-Earth asteroids. Thanks near-Earth asteroid explorers
PDC: Bruce Betts/The Planetary Society; Planetary Radio: Antonio Perance/The Planetary Society; Shoemaker Grant photo: Morocco Oukaïmeden Sky Survey
to your support, over its 22-year history the OSIRIS-REx and Hayabusa2,
program has awarded $382,000 in 56 awards to Israel’s Beresheet lunar lander,
astronomers in 18 countries on 6 continents. The InSight on Mars, the Interna-
Bringing Together the tional Space Station, future
plans for humans in deep
World’s Experts space, and many more. The
PLANETARY DEFENDERS like you are helping to pages provide background
protect Earth from dangerous asteroids. Every 2 information and frequently
years, scientists, engineers, and decision makers updated news briefs. See them
gather together at the International Academy all at planetary.org/missions.
of Astronautics Planetary Defense Confer-
ence to discuss the latest in finding, tracking,
characterizing, and deflecting asteroids. Your
LEFT Mat Kaplan hosted
support of The Planetary Society helped make Planetary Radio Live at
this conference happen. This year’s confer- the 2019 Planetary Defense
ence took place 29 April to 3 May 2019 in the Conference public event.
Washington, D.C. area. The Planetary Society
was a primary sponsor of the conference, and TOP RIGHT Shoemaker
Planetary Society chief scientist Bruce Betts Grants support upgrades
served on the organizing committee and pre- to observatories such as
sented 2 papers. In association with the confer- this one in Morocco.
ence, The Planetary Society hosted a public grants have been used to purchase more sensitive
BOTTOM RIGHT To date,
event at the University of Maryland: “Bill Nye vs. cameras, equipment to allow remote-controlled
the grants comprise 56
the Asteroids.” It featured not only Bill Nye but observation, and telescope improvements.
awards to astronomers in 18
also several asteroid-threat experts and NASA At the Planetary Defense conference, The countries on 6 continents.
chief scientist Jim Green. Mat Kaplan hosted Planetary Society announced a new call for
an episode of Planetary Radio Live with a panel proposals. The proposal deadline is 30 July
of asteroid experts. You can hear the show at 2019. For more information, including updates
planet.ly/pdc19 and see videos from the public on the impressive work enabled by grants to
event and conference at planetary.org/defense. past winners, visit planetary.org/neogrants.
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 5
More on each story can be found online! Use the link provided.
YOUR IMPACT
You’re an Explorer
Planetary Society
on the Road
WE WANT SOCIETY members (and not-yet
Society members) to have more opportunities
to get together and celebrate our passion for
space. Want to know what events are coming
up? Check out planetary.org/events. Here
are a few highlights from recent months.
SXSW PANEL: SPACE EXPLORATION
FOR ALL At this year’s South by Southw est
Festival, Planetary Society CEO Bill Nye joined
Richard Garriott, one of the private astro-
nauts from Soyuz TMA-13’s mission to the
International Space Station, and Molly Cain, LightSail 2 Spacecraft
former director of venture at U.S. Homeland
Security, for a conversation about the present
Launching Soon
and future business opportunities in space. CITIZEN PARTICIPATION in space is about to
Listen to the panel at planet.ly/2019sxsw. launch to new heights. Your LightSail 2 space-
craft will be on the next flight of SpaceX’s Falcon
EXTREME STEA2M The Planetary Society
Heavy rocket as early as 22 June 2019. To
joined with other partners to offer STEA2M
prepare for this milestone, the LightSail 2 team
Fair: Extreme STEA2M, Extreme Fun. More
completed final testing and made some small
than 20,000 students, teachers, and families
ABOVE Planetary Society improvements. In February, the team carried
LightSail lab photo: Bruce Betts/The Planetary Society; Launchpad: SpaceX
attended a fun-filled day full of hands-on
events empower the out an Operational Readiness Test (ORT) using
activities that included an inspiring talk by CEO
public to participate in BenchSat, the tabletop demonstrator that mimics
Bill Nye, a live recording of Planetary Radio with
space exploration. the solar sail flight spacecraft. An ORT simulates
Mat Kaplan, and myriad educational opportu-
major spacecraft events, allowing the team to
nities. Visit planet.ly/stea2m19 to listen.
TOP RIGHT Engineers install practice and refine procedures. The team also
LightSail 2 in its deployment YURI’S NIGHT is a global celebration of tested some minor software updates and then
device. From left: Alicia humanity’s past, present, and future in space. uploaded them to the flight computer. In early
Johnstone, David Pignatelli,
Society members all over the world attend May, we shipped LightSail 2 to the Air Force
and Stephanie Wong.
local Yuri’s Night events in commemoration Research Laboratory in Albuquerque, where it
of Yuri Gagarin’s pioneering 12 April 1961 was reintegrated with the Georgia Tech space-
BOTTOM RIGHT In February
2018, SpaceX launched its flight and the first space shuttle launch 20 craft Prox-1. At the time of this writing, we are
first Falcon Heavy. LightSail years later. If you missed out this year or didn’t expecting to ship to Florida in late May to be inte-
will launch on Falcon have one near you, know that anyone can grated with the rocket. For the latest details, keep
Heavy’s third flight. create a Yuri’s Night event. yurisnight.net your eye on sail.planetary.org. Go LightSail!
6 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019
Bricks Hit
the Ground
THERE MAY BE more stars
in the Hollywood Walk of
Fame, but the real stars in our
universe are the members who
have purchased a piece of rock.
Another set of 61 planetary
pavers has arrived, and they are
now installed in the walkway
into your Planetary Society
headquarters. The proceeds
of the brick program support
the purchase of capital equip-
ment items. Check out the
inspiring and heart-warming
messages written by your
fellow members by heading to
You’re an Advocate planetary.org/bricks and
tapping “Find Your Brick.”
You’re Building Support 100 Members.
for Planetary Science 1 Day of Action.
IN FEBRUARY, The Planetary Society sup- IN MARCH, 100 members of The Planetary
ported the reestablishment of the Planetary Society carried out a remarkable day of space
Science Congressional Caucus in the new advocacy at the U.S. Congress. They came
116th Congress with new co-chairs Rep. from 25 states and the District of Columbia.
Derek Kilmer (D-WA) and Rep. Steven Palazzo Some were grade-school students. Some were
(R-MS). The caucus, which was first created retired. A few were professional scientists and
in the 115th Congress, expired with last engineers. They were men and women from all
November’s election. Your chief of Washington walks of life, but they all shared one thing: they
operations, Brendan Curry, has been working so believed in the promise of space science and TOP 100 members of The
to increase membership in the caucus, which exploration that they traveled to Washington on
Planetary Society show
Day of Action photos: Antonio Perance/The Planetary Society
their passion for space at
now boasts 20 members. The partial govern- their own dime to advocate directly to Congress.
the 2019 Day of Action.
ment shutdown earlier in this year and the Participants attended a half-day advocacy
recent announcement of an amended budget training session before breaking into groups BOTTOM LEFT Members
for NASA in May has delayed the introduc- to visit 127 Congressional offices. The energy, received a science briefing
tion of the President’s budget request for passion, and enthusiasm of these dedicated on New Horizons during
fiscal year 2020. The Planetary Society is members of The Planetary Society serve as the Day of Action.
keeping a close eye on these events and will an ongoing source of inspiration for Planetary
work to keep our members informed. Follow Society members and staff. Learn more about BOTTOM RIGHT NASA
planetary.org/caucus for all the developments. the Day of Action at planet.ly/action2019. Administrator Jim
Bridenstine addresses
Planetary Society members like you make this work possible. Thank you! Planetary Society members
as part of the Day of Action.
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 7
GET INVOLVED
Help Defend the Earth From Asteroids
OUR PALE BLUE DOT is sitting in a cosmic shooting gallery. Asteroid and comet impacts,
while not common, are very real threats. You can make an impact (get it?) in the battle against
threatening asteroids. Here’s how:
107
total known
near-Earth comets
GET EDUCATED
Check out our new Asteroid Defense
TEACH OTHERS
Download our Planetary Defense
896
total known NEOs
101, a short course about the threat of
asteroid impact and what we can do
to prevent it. courses.planetary.org
Toolkit and raise awareness of
the asteroid threat in your local
community. planetary.org/volunteer
larger than 1,000m
8,609
total known NEOs
BE LOUD
larger than 140m
Current known NEO totals reported at cneos.jpl.nasa.gov; Bennu image: NASA/Goddard/University of Arizona
20,141 SUPPORT DIRECTLY #AsteroidDay is 30 June. This United
Nations-recognized global awareness
For 22 years, the Society has sup- day marks the 111st anniversary of the
total known ported asteroid hunters through our Tunguska impact event. Tell your repre-
near-Earth asteroids Shoemaker Near-Earth Object Grants. sentatives in Congress to prioritize the
Donate by 30 June, and your gift will issue of protecting Earth from asteroids
20,248
be matched, dollar for dollar, up to so that when the next threat arrives,
$15,000. planet.ly/shoemakerdonate we’re ready. planetary.org/neopetition
total known
near-Earth objects
ABOVE Near-Earth asteroid
Bennu, the target of the
BE VISIBLE
The city-sized asteroid that doomed
OSIRIS-REx mission, was
the dinosaurs 65 million years ago
named by then-9-year-
old Michael Puzio in a shall not be forgotten. Remember
Planetary Society contest. Chicxulub! Buy your shirt and support
our efforts. planet.ly/cxshirt
8 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019
SOCIETY TRAVEL
Society Travel
MORE WAYS TO GET INVOLVED Adventures for You
IN SPACE EXPLORATION THIS SEASON and Your Friends
LIGHTSAIL 2
The world’s first controlled solar sail
flight in Earth orbit is ready for launch—
thanks to you. Keep your eyes on
sail.planetary.org for updates about our
launch aboard a SpaceX Falcon Heavy rocket.
TOTAL SOLAR ECLIPSE
SOUTH PACIFIC, CHILE,
AND ARGENTINA
On 2 July, invite your friends
to witness one of humanity’s
most transformative celestial
experiences: a total solar eclipse.
ANGKOR WAT & BINTAN ISLAND “RING OF FIRE”
planet.ly/190702eclipse
18–27 DECEMBER 2019
Explore the mysteries of Angkor Wat.
Discover the amazing 500 Lohan statues
on Bintan Island beneath the “Ring of Fire”
of the 26 December annular eclipse. This
is a once-in-a-lifetime opportunity!
CELEBRATE THE GREATEST
FEAT OF HUMAN EXPLORATION ALASKA AURORA BOREALIS 2020
IN HISTORY WITH US 27 FEBRUARY—4 MARCH 2020
Humans’ first footprints marked Join us as we explore the great beauty
the Moon 50 years ago on 20 July. of Alaska in winter and see the famed
Listen to the fascinating stories aurora borealis, or northern lights,
behind the mission in our multi-part the greatest light show on Earth.
podcast special, The Political History
of Apollo. planet.ly/apollo50 ARIZONA SKIES & NEW DISCOVERIES 2020
19–26 APRIL 2020
What does the Apollo anniversary Explore this desert paradise, meet
mean to you? Share your story at scientists, and see observatories in the
myapollostory@planetary.org or astronomy capital of the world: Tucson. See
Biosphere 2, Kitt Peak, and the stunning red
#MyApolloStory on social media.
rocks in Sedona. Marvel at the night sky.
ARGENTINA TOTAL SOLAR ECLIPSE
The Planetary Society; NASA; Getty Images
8-19 DECEMBER 2020
SPACE ADVOCACY 101 Join us north of San Martín de Los Andes to
School’s out! But that doesn’t see the total solar eclipse on 14 December
mean classes are done. Now’s 2020. Visit Buenos Aires and Iguazu Falls
for an extraordinary eclipse adventure!
the time to level up your United
States space advocacy expertise.
For more information, please contact
Take our free online course at
Terri or April at Betchart Expeditions
courses.planetary.org.
Inc., 800-252-4910, or e-mail
info@betchartexpeditions.com
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 9
WHAT’S UP? by Bruce Betts
IN THE SKY
On 2 July, there will be a total solar eclipse visible from parts of
the southern Pacific, Chile, and Argentina, with a partial solar
eclipse visible from much of South America. On 16 July, a partial
lunar eclipse will be visible throughout much of Europe, Africa,
and western and central Asia. The Perseid meteor shower peaks
12-13 August, with increased activity several days before and after,
but the Moon will be almost full at the peak, limiting the number
of meteors visible. Bright Jupiter and yellowish Saturn are visible
in the evening sky going from east to west as the weeks pass. ABOVE One of the last photos returned by SpaceIL’s Beresheet
lander, which crash-landed on the Moon on 11 April 2019.
Where We Are
RANDOM An At-A-Glance Spacecraft Locator
SPACE FACT THE LAST QUARTER has seen few changes in the roster of plan-
etary exploration spacecraft. SpaceIL’s lunar lander Beresheet
is now on the lunar surface. Its descent on 11 April seemed to
The 6 Apollo missions that landed humans on the Moon
go nearly perfectly. Unfortunately, a cascade of events shortly
brought to Earth a total of 382 kilograms (842 pounds)
before its planned landing caused it to hit the ground too fast,
of rocks, core samples, pebbles, sand, and dust from the
lunar surface. There were 2,200 separate samples. and it did not survive.
I’ve corrected an earlier omission (spotted—as they always
are—by a sharp-eyed reader): the map at right now includes
ESA’s Gaia star-mapping spacecraft, which orbits in step with
TRIVIA CONTEST Earth at the gravitationally stable L2 point, farther from Earth
than the Sun.
Chang’e-4 and Yutu-2 are now past their prime mission
and are in their extended mission phases. Their companion
Our December Solstice contest winner is Joel Beebe of Ann Arbor,
SmallSat, Longjiang-2, will crash into the Moon on 31 July to
Beresheet: SpaceIL; Loren A. Roberts for The Planetary Society after a concept by Olaf Frohn
Michigan. Congratulations! The question was: Who were the final
members of the backup crew for the Apollo 8 mission? The answer: bring its mission to an intentional end. Parker Solar Probe is near
Neil A. Armstrong, Edwin E. Aldrin, Jr., and Fred W. Haise, Jr. aphelion as of 1 July and will reach its third death-defying solar
perihelion on 1 September. BepiColombo completed its near-
Try to win a copy of Astronomy for Kids: How to Explore Outer Space Earth commissioning phase on 5 April and is now settling into
with Binoculars, a Telescope, or Just Your Eyes! by Bruce Betts and a its long-cruise phase. Earlier this year, the ESA-JAXA Mercury
Planetary Radio T-shirt by answering this question: mission was racing ahead of Earth on an inside track, but its
elliptical orbit has now taken it farther from the Sun than Earth,
What was the first spacecraft mission to return
allowing Earth to catch up. It will return to Earth’s neighborhood
samples from a comet?
in April 2020 for a flyby.
Email your answer to planetaryreport@planetary.org or mail your answer to The Plan-
etary Report, 60 S. Los Robles Ave., Pasadena, CA 91101. Make sure you include the At Mars, InSight has struggled to bury its heat probe beneath
answer and your name, mailing address, and email address (if you have one). By enter- the surface, but its seismometer is recording good data and has
ing this contest, you are authorizing The Planetary Report to publish your name and
hometown. Submissions must be received by 1 September 2019. The winner will be finally detected one very small Marsquake. Scientists are hopeful
chosen in a random drawing from among all the correct entries received.
for more. Curiosity recently completed its first drilling activity
For a weekly dose of “What’s Up?” complete with humor, a weekly trivia contest, and
a range of significant space and science-fiction guests, listen to Planetary Radio at in Glen Torridon, a clay-rich valley at the base of Mount Sharp.
planetary.org/radio.
Out at Jupiter, Juno will be swinging through 2 perijove passes
on 21 July and 11 September.
10 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019EMILY STEWART LAKDAWALLA is
Gaia
The Planetary Society’s senior editor Earth-Sun L2
On Moon:
and planetary evangelist.
Chang’e-3
Chang’e-4
Beresheet
Planets and spacecraft
Queqiao Moon positions are shown for
Longjiang-2 1 July 2019 or Julian
date 2458665.5
ARTEMIS
Chang’e-5 T1 Julian dates, used by
Lunar astronomers, count up the
Reconnaissance Earth days since noon Universal
Orbiter Time on 1 January 4713 BC.
Mars year 35/solar longitude 46.6°
Solar longitude measures Mars’ season,
with equinoxes and solstices occurring ACE
SOLSTICE (SOUTHERN SUMMER)
SOLSTICE (NORTHERN SUMMER)
at 0°, 90°, 180°, and 270°. Mars year EQUINOX
Mars 1 began at northern vernal equinox WIND
Reconnaissance Earth-Sun L1 “STAND” INDICATES SMALL BODY
Orbiter (solar longitude 0°) on 11 April 1955. POSITION ABOVE OR BELOW THE ECLIPTIC
SOHO
MAVEN
Curiosity DSCOVR
Mars InSight ExoMars
Express Mars Trace Gas
Odyssey Orbiter
Mars
Orbiter Hayabusa2
Mission
Ryugu
STEREO Behind
Parker
Solar
Probe
Akatsuki
Venus BepiColombo
Sun Earth
Mercury
COMING IN 2019
Chang’e-5 launch/landing
LightSail 2 launch Spitzer
Bennu
OSIRIS-REx
Chandrayaan-2 launch Mars STEREO Ahead
Main
Cheops launch Asteroid
Belt
COMING IN 2020
BepiColombo Earth & Venus flybys
Parker Solar Probe Venus flyby
Korea Pathfinder Lunar Orbiter launch
Many Mars mission launches
Hayabusa2 Earth return
Voyager 1
Neptune
New Horizons
Uranus
Saturn
Jupiter
Juno
Cold
Classical
Voyager 2
Kuiper
Belt
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 11Apollo 11 Little West
Crater Panorama
by Mike Constantine
RIGHT Lunar Reconnaissance APOLLO 11’S LANDING on 20 July 1969 was the 30-meter-wide Little West Crater, landing with
Orbiter was sent to the Moon day humans first set foot on another world. For only 25 seconds’ worth of fuel remaining.
in 2009 to map future human
the risky, challenging endeavor, NASA sought Capturing this panorama was not part of the
landing sites. It acquired
this view of the Apollo 11 a smooth landing site, one lacking craters or originally scripted mission plan. Armstrong
landing site on 5 November mountains. Following years of survey by lunar took time out of the scheduled activities to
2011. Armstrong’s tracks orbiters, NASA selected Mare Tranquillitatis venture 60 meters east of the lunar module to
out to the rim of Little West for Apollo 11, as it was a flat plain of basalt with Little West, the hazard he had to avoid during
Crater are still clearly visible. few topographic features. Ironically, during the landing. It was the largest feature Arm-
descent, Mission Commander Neil Armstrong strong could see from the landing site. The
had to take semiautomatic control of the lunar white object in the foreground is the handle
module to avoid a large boulder field and the of the Apollo Lunar Surface Close-up Camera,
12 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019a device that allowed the crew to take close-up We’re celebrating each
photographs of the lunar surface. Apollo mission’s 50th launch
In 2005, upon seeing this panoramic anniversary with a brand-
NASA/Mike Constantine; Inset: NASA/GSFC/ASU
assembly, Armstrong told me that it didn’t look new online resource page.
nearly as big as it had when he was there and Visit planetary.org/apollo
that visiting the crater had been a “worthwhile for photos, maps, timelines,
deviation.” For more of my conversation with videos, and more.
Armstrong, visit planet.ly/ap11story.
Mike Constantine is the author of Apollo: The 50m
Panoramas and director of moonpans.com.
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 13MARTIN RUBIN, a researcher at the
University of Bern, is on Rosetta’s mass
spectrometer team. CECILIA TUBIANA, at
the Max Planck Institute for Solar System
Research, is on Rosetta’s camera team.
RIGHT ESA’s Rosetta mission
accompanied comet 67P/
Churyumov-Gerasimenko in
its orbit around the Sun from
August 2014 until its landing
on the comet in September
2016. The comet was most
active just after perihelion in
August and September 2015,
ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/Jacint Roger Pérez/Emily Lakdawalla
its jets carrying streams of
primordial dust into space.
Rosetta’s Ancient Comet
ESA Mission Unlocks the Secrets of Icy Relics
ROSETTA IS A European Space Agency mission in their evolution. Comets are dynamic
with contributions from its member states worlds with dramatically varying activity.
and NASA. Operating such a complex mission With Rosetta, we sought to visit a quiet comet
with its 11 instruments and Philae lander is a and then accompany it on its path into the
success story in itself, but Rosetta’s greatest inner solar system, observing its evolution
success is the science it delivered. Although while approaching the Sun, passing through
the mission is over, the investigation of the perihelion, and moving back into the outer
data acquired by its instruments is bound to solar system.
keep us busy for many years to come. Rosetta One driving question for Rosetta concerns
succeeded only because of the tremendous the origin and history of comet 67P: how pri-
work and dedication of the more than 2,000 mordial is this cometary nucleus? How did
engineers, technicians, and scientists involved. it evolve since its formation 4.5 billion years
Prior comet missions have only briefly ago? How is it evolving now? Here, we present
visited their targets, seeing just one moment a few selected highlights of the mission, but
14 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019ROSINA Rosetta Orbiter
Spectrometer for Ion MIRO Microwave CONSERT Comet Nucleus
and Neutral Analysis Instrument for the Sounding Experiment by
Rosetta Orbiter Radio-Wave Transmission
ROSINA DFMS Double- Investigates Studies the internal
Focusing Mass Spectrometer outgassing from structure of
Determines composition of the nucleus and the comet
the comet’s atmosphere development with Philae
COSIMA Cometary of the coma NAVCAM Navigational
Secondary Ion Mass Cameras 5° field of view;
MIDAS Micro-Imaging Dust Analyser Studies 1,0241,024 pixels;
Analysis System Studies the composition of the dust 0.085 mrad/pixel;
dust environment of the comet in the comet’s coma monochrome
RPC Rosetta Plasma
Consortium Studies GIADA Grain Impact
plasma environment Analyser and Dust
RPC IES Ion and Accumulator Measures the
Electron Sensor number, mass, momentum,
and velocity distribution
ROSINA RTOF Reflection of dust grains in the
Time-of-Flight Mass near-comet environment
Spectrometer Determines
composition of the ROSINA COPS Comet Pressure
comet’s ionosphere Sensor Measures the temperature,
RPC ICA Ion velocity, and density of the gas flow
Composition Analyser
RPC LAP VIRTIS Visible and Infrared Thermal Imaging
Langmuir Probe Spectrometer Studies the nature of the comet
nucleus and the gases in the coma
OSIRIS Optical, Spectroscopic, and Infrared Remote
Imaging System Color scientific camera system
OSIRIS NAC Narrow-Angle Camera 2.2° field of view;
2,0482,048 pixels; 0.0186 mrad/pixel; 12 filters
OSIRIS WAC Wide-Angle Camera 12° field of view;
2,0482,048 pixels; 0.191 mrad/pixel; 14 filters
PHILAE (stowed)
RPC MIP Mutual
Impedance Probe
RPC MAG
Fluxgate ROSETTA
ALICE Ultraviolet Imaging
Spectrometer Characterizes
Magnetometer
RPC LAP
INSTRUMENT
composition of the comet
nucleus and coma
Langmuir Probe INVENTORY
this is just scratching the surface and is by no material at a rate of a few kilograms per ABOVE Rosetta is a
means complete. second. Rosetta inspected the comet very cornerstone mission of ESA.
closely, selecting a landing site and then The spacecraft carried 11
science instruments, some
RAPIDLY CHANGING NUCLEUS deploying Philae late in 2014 while the low
of them having multiple
After more than 10 years of flight, Rosetta activity provided a safer environment for close components, contributed by
arrived at comet 67P on 6 August 2014. From approaches. Over the course of the mission, scientific institutes in ESA
earlier Hubble Space Telescope observations, the outgassing gradually increased to several member states and the U.S.
we expected 67P to be more of a diamond- hundred kilograms per second during its peak The spacecraft was huge—a
box 2.8 by 2.1 by 2 meters in
shaped object. The peculiar bilobate shape activity some weeks after perihelion.
size with a wingspan of 32
of the comet was a big surprise. The resem- Rosetta and Philae’s instruments worked meters. The Philae lander
blance to a rubber ducky was striking. The together to reveal the details of the struc- had 10 more instruments.
team quickly adopted the duck nomenclature ture of the comet’s surface and interior. The
Emily Lakdawalla, Charles H. Braden, and Loren A. Roberts for The Planetary Society
not just for the humor of it but as a useful CONSERT experiment passed radio waves
orientation: when somebody talked about the through the nucleus between the orbiter and
neck, everybody knew where to look. the lander. The waves did not bounce off many
Rosetta’s OSIRIS camera images of 67P internal boundaries, so the interior is probably
revealed a nucleus with a rich variety of mostly homogeneous. The surface itself is
landforms such as steep cliffs, terraces, and very dark, very hard, very dry (lacking much
circular pits, many of which exposed internal water ice), and rich in organic compounds.
layering. The layers do not match across the High-resolution images of the southern
two lobes, suggesting that the nucleus began hemisphere acquired after December 2015
as two independent objects that merged in revealed a clear north-south dichotomy
a gentle collision. We also saw a contrast across the nucleus’ surface. The southern
between smooth, dust-covered areas and hemisphere appeared rugged and more con-
rugged terrains. solidated, with little dust and a flatter terrain
At the time and place of arrival, well beyond (fewer cliffs and pits) than the northern hemi-
3 AU, the comet’s activity was low, releasing sphere. The consensus is that the southern
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 15DEC 2015 5 SEP 2015 Comet solstice (southern summer peak)
Rosetta starts closer approaches 13 AUG 2015 Comet perihelion Jupiter
as comet activity decreases
30 SEP 2015
23 MAR 2016 Far excursion 11 MAY 2015
Comet equinox toward Sun Comet equinox (start of short,
(1,500km intense southern summer); Rosetta
from comet) increases distance from comet
rocky dust material in addition to ices, it must
30 MAR 2016 Earth
Far excursion away
have a high porosity of more than 70 percent.
from Sun (1,000km Any object moving faster than approximately
from comet) 1 meter per second possesses enough energy
MAY-JUL 2016 14 FEB 2015
Close encounter (approach to 6km) to escape the gravitational pull of the comet.
Global mapping
at close range This corresponds to walking speed on Earth!
(down to 8km) During gravitationally bound orbits, the space-
Mars
AUG-SEP 2016 Elliptical orbits with craft moved even slower than that.
very close approaches (down to 2km) 12 NOV 2014 As Rosetta watched, the comet approached
30 SEP 2016 Philae landing
the Sun, its surface warmed up, and buried
End of mission SEP-OCT 2014
67P Global mapping at close range (about 8km)
ices sublimated. The expanding gases dragged
dust particles along into jets. This activity led
8 JUNE 2011 6 AUG 2014
Rosetta Arrival at 67P
to profound changes across the nucleus. Cliffs
enters collapsed, fractures gaped wider, a 13-ton
hibernation 10 MAY 2014
Approach science begins boulder moved, scarps appeared and/or
receded, and ripples of fine-grained material
20 MAR 2014
formed and disappeared. Over time, the spin
First sight of comet destination
rate increased. Some day, that increased spin
Rosetta
may pull the comet apart along fissures we
can see in the neck.
20 JAN 2014 All of these changes resulted from the
Rosetta comet losing mass. Comparing Doppler
wakes
up from measurements early and late in the mission
hibernation yielded an estimated mass loss of 10.5 million
tons, about 0.1 percent of the comet’s total.
hemisphere is more representative of the This is equivalent to a 70-centimeter-thick
comet’s interior, while the north is cloaked (2-foot-thick) layer of material removed from
under a blanket of fallback dust that origi- the comet nucleus during each orbit. Yes, this
nated from the southern hemisphere. means that comets have a finite lifetime.
ABOVE Being solar powered, The images permit us to measure the
Rosetta had to hibernate nucleus’ dimensions. The small lobe measures COMETS: NOT EARTH’S MAIN
when it reached 4.5 AU in
about 2.6 by 2.3 by 1.8 kilometers (1.6 by 1.4 WATER SOURCE
June 2011. After waking, it
rendezvoused with 67P by 1.1 miles), while the large lobe is about In planetary science, elements that have a low
on 6 August 2014 and 4.1 by 3.3 by 1.8 kilometers (2.5 by 2.1 by 1.1 sublimation temperature are often referred to
accompanied the comet miles). Radio Science Investigation (RSI) mea- as “volatiles.” A comet outgasses more vola-
through its changing seasons surements of Rosetta’s Doppler-shifted radio tiles when it’s closer to the Sun and less when Emily Lakdawalla and Loren A. Roberts for The Planetary Society
and perihelion passage until
signal gave us the comet’s mass (about 1013 it’s farther away. Like planets, comets can also
the mission was brought
to an end on 30 September kilograms). Together, these numbers yield have seasons. Comet 67P has pronounced
2016. Distances are given with an estimated density of half that of water ice. seasons due to the tilt of its rotation axis with
respect to the comet surface. Since the comet certainly contains denser, respect to the orbital plane. The northern
MARTIN RUBIN is a senior lecturer at the University of Bern in the Department of Space Research
and Planetary Sciences. His research interests cover a wide range of objects in our solar system, in
particular the investigation of comets by means of spacecraft exploration. CECILIA TUBIANA is a
research scientist at the Max Planck Institute for Solar System Research in Göttingen (Germany). Her
main research interest is comets. She is part of the team that designed, planned, and commanded the
Rosetta OSIRIS comet images.
16 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019ROSETTA’S ANCIENT COMET
hemisphere summer is much longer and origin. If this is true, then organic chemicals LEFT The northern (left)
weaker compared to the short and intense detected by the ROSINA, COSAC, and Ptolemy and southern (right)
summer around perihelion in the south, and mass spectrometers on both the lander and hemispheres of 67P. The
southern hemisphere came
the ROSINA, MIRO, OSIRIS, and VIRTIS instru- the orbiter would have also found their way to
Left: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/Emily Lakdawalla; Right: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/Emily Lakdawalla after Xuanyu Hu et al. (2016)
into view in mid-2015 during
ments monitored these seasonal variations. the early Earth. Organic materials that Earth its summer, which coincides
The comet’s releases of gas and dust must potentially received from comets include a with perihelion and the
originate at or near the nucleus’ surface. Yet host of molecules relevant to early life, such peak of comet activity.
despite all of the changes we witnessed, we as the simplest amino acid: glycine.
had difficulty locating active areas or exposed
ices on the surface of the nucleus. On rare MAGNETIC FIELD SURPRISES
occasions, the VIRTIS instrument detected As Rosetta escorted the comet from 3.6 to 1.2
patches of water and carbon dioxide frost on AU and out again, the RPC instrument suite
the dawn side of the nucleus. witnessed the ever-changing comet interac-
One of the surprising results was the tions with the solar wind. When hit by solar
detection of abundant amounts of molecular radiation and energetic particles, the gases
oxygen (O2) by ROSINA and Alice. We saw that emanating from the nucleus lose electrons,
the abundance of oxygen correlated well with becoming charged particles themselves.
water but less well with molecular nitrogen. Because of their charge, they interact with
The relationship between oxygen and water the solar wind, thus forming a magnetosphere
50m
in the comet likely dates back to their origin around the comet that grows as the outgas- ABOVE As Rosetta watched,
in the interstellar medium before the solar sing increases. For its part, the Philae lander the comet’s surface changed.
system formed. We also studied the isotopes magnetometer detected no permanent mag- Between September 2014 (top)
and March 2015 (bottom),
of hydrogen in the comet’s water and came netization of the nucleus, so the comet did not honeycomb features
to a similar conclusion: the comet’s water originate inside a strong magnetic field that appeared in depressions
originated in the interstellar medium. left its imprint in the incorporated material. on the Ma’at region on the
We were surprised by the relatively large As the comet got closer to the Sun, the comet’s “head.” By the end of
amount of heavy hydrogen (deuterium) in comet’s magnetosphere grew and eventually 2015, the surface texture had
reverted to an appearance
the comet’s water. That discovery ruled out blocked the solar wind from reaching the
similar to that in 2014.
a popular hypothesis for the origin of Earth’s nucleus’ surface. The comet formed a “dia-
water. We now know that comets of 67P’s magnetic cavity,” a region close to the nucleus
type were not a major source of the water without any detectable magnetic field. Comet
that became Earth’s oceans. However, noble scientists had seen a diamagnetic cavity before
gas measurements suggested that maybe 22 during Giotto’s 14 March 1986 encounter with
percent of Earth’s atmosphere has a cometary comet 1P/Halley. Contrary to our expectations,
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 17d
a
ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S/Langevin et al. (2016); ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
b
c
500μm
ABOVE Dust particles imaged though, the shape of 67P’s cavity changed all system formation. Nearly half of the mass
by COSIMA were diverse. the time. Rosetta’s slow velocity around the of 67P’s dust comprises organics. These are
In this image, (a) marks comet and the dynamic nature of the cavity’s not small molecules; they are huge, carbon-
a compact particle, while
shape meant that the boundary of the diamag- rich macromolecules similar to those found in
(b), (c), and (d) are particle
clusters that were more or netic cavity swept across the nearly station- carbonaceous chondrite meteorites. However,
less glued together before ary spacecraft more than 600 times over the unlike meteorites, 67P’s dust contained
impacting the instrument. course of a few months around perihelion. silicate (rocky) minerals without any water
in their crystal structures. The lack of water
ABOVE RIGHT In some
COMET DUST’S ANCIENT ORIGINS in 67P’s mineral particles is evidence that the
places, the comet appears
to be a coherent block The environment of 67P proved to be quite comet has never been part of a larger object
crossed with long fissures; in dusty. At times, there would be so much dust containing liquid water.
other places, this material near the nucleus that wayward specks would
appears to break up into confuse Rosetta’s star trackers, and navigators THE COMET’S STORY
boulders. Yet other areas had to back the spacecraft significantly away Taken together, Rosetta’s study of 67P has
seem smooth, with what
from the nucleus to avoid danger. However, helped us see past the modern appearance of
appear to be collapse pits.
Rosetta stayed as close as possible because it the comet and understand its origin. We have
was at 67P to study this material. Dedicated learned that the comet is made of primitive
instruments investigated the amount, com- material, preserved almost unchanged since
position, and shapes of dust particles around the comet accreted in the distant reaches of
the comet. Rosetta studied dust on all scales, the protoplanetary disk that would eventually
from meter-sized boulders seen in camera become our solar system. The comet contains
images to sub-millimeter-sized fluffy aggre- materials that originated from a wide range
gates seen by the COSIMA microscope to of distances from the Sun and even material
tens of nanometers measured by the MIDAS from the interstellar medium that predated
atomic force microscope. The GIADA instru- the formation of the solar system.
ment counted particles, detecting both loosely The comet’s appearance today is very dif-
and densely packed particles. Loosely packed ferent from its primordial one and changes
The Rosetta team has
agglomerations likely date from the formation with every perihelion pass. Some comets, so-
exerted considerable effort
processes operating in the early solar system. called sungrazers, do not survive their first
to make all Rosetta data
The densely packed particles resembled those close passage at the Sun, while others, such as
publicly available. Would you
brought back to Earth by NASA’s Stardust 1P/Halley, may have already visited the inner
like to rummage through
mission to comet 81P/Wild 2. solar system thousands of times. On its current
thousands of images to
COSIMA measured the elemental abun- orbit, 67P will return, but how many times—
find your personal favorite?
dances of the dust in 67P and found them to and in how many pieces—nobody knows.
Go to rosetta-osiris.eu and
match the elemental abundance of the entire NASA is now considering a mission to bring
imagearchives.esac.esa.int.
solar system, suggesting that the comet is back a sample from 67P. One day, we may
a very primitive body dating back to solar return to see how much it has changed.
18 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019MAKOTO YOSHIKAWA is JAXA’s mission
manager for Hayabusa2. ELIZABETH TASKER
is an associate professor at ISAS, JAXA.
LEFT The moment that
Hayabusa2 contacted
asteroid Ryugu, it fired a
bullet through its sampler
horn (center) to knock
material loose from the
surface and then immediately
fired its thrusters to ascend.
This photo, taken from
an altitude of 8 meters,
demonstrated the success
of the bullet; dark-colored
fragments tumble in
Hayabusa2’s shadow in the
JAXA/Tokyo University/Kochi University/Rikkyo University/Nagoya University/Chiba Institute of Technology/Meiji University/Aizu University/AIST
space beneath the craft.
Treasure Hunting With Hayabusa2
JAXA’s Fleet of Mini-Robots Lands on a World Full of Surprises
IN THE EARLY hours of 22 February, light MISSION TO A NEO
was just beginning to brighten the campus Near-Earth objects (NEOs) like Ryugu are
of JAXA’s Institute of Space and Astronautical thought to have once been part of larger
Sciences (ISAS) in Kanagawa, Japan. It should bodies that orbited in the asteroid belt
have been a quiet time, but the Hayabusa2 between Mars and Jupiter. Collisions between
control room was packed with people. We asteroids and the push from solar radiation
were about to land on an asteroid. can move these bodies onto slightly differ-
More than 340 million kilometers (210 ent trajectories. These small changes can
million miles) away from us, our spacecraft have orbital dynamics effects, such as a close
hovered only meters above asteroid 162173 approach to Mars that greatly changes the
Ryugu, making sure of its targeting. Then, like asteroid’s orbit so that it approaches the orbit
its namesake peregrine falcon, Hayabusa2 of Earth as a NEO.
descended and snatched a sample. When we The Hayabusa2 mission is analyzing Ryugu’s
received the images from the touchdown, we composition through remote observation.
were surprised to see a dark stain over the These data, together with the examination of Read this article
sample site. Ryugu was already the darkest returned samples, should give us clues to this in Japanese at
world ever visited; our brief touchdown had asteroid’s parentage. We can use this history planet.ly/haya2jaxa
left it darker. to map the movement of water and organics
T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019 19162173 Ryugu 1.0x0.9km
through the solar system and to the terrestrial Ryugu is roughly 1 kilometer (0.6 miles)
worlds. While returning a sample is a chal- across and is shaped like a spinning top (or
lenging and risky endeavor, the analyses that abacus bead), with a thick equatorial ridge.
can be performed in a laboratory back here One of the most visually striking features is a
on the ground greatly outstrip anything that 290-meter-diameter crater that straddles the
can be achieved in space. equator, which we named Urashima. Urashima
The predecessor of Hayabusa2—the space- is the name of a character in Japanese legend
craft Hayabusa—returned to Earth with a who traveled to a dragon’s underwater palace,
sample from an S-type asteroid, 25143 Itokawa, Ryugu castle, and brought back a treasure box.
in 2010 (see The Planetary Report 30, no. 4). The top shape was a surprise. Rapidly
Ryugu is a C-type, or carbonaceous asteroid, rotating bodies experience a centrifugal force
a categorization for primitive asteroids that that is the same outward push you feel on
are expected to contain carbon-rich material. a merry-go-round. This can push material
One theory for how Earth became habitable toward the equator to create the bulging
suggests that our young planet was pelted shape of a spinning top. However, Ryugu
with meteorites from asteroids like Ryugu. rotates only once every 7.6 hours, which is
These delivered water and simple organics too slow for reshaping by centrifugal force to
101955 Bennu 0.5km
that formed our seas and triggered the start occur. If rotation is the cause of the top shape,
of biology. then the asteroid must have been spinning
Testing this hypothesis drives the science faster in the past.
behind Hayabusa2. If samples from asteroid Seen through the 7 different filters on the
Ryugu are found to contain hydrated (water- telescopic optical navigation camera, Ryugu
bearing) minerals or organic compounds appears homogenous in color, with a slight
that match those on Earth, then C-type aster- blue tinge to the equatorial ridge. The color
oids may be a key component to forming a homogeneity is consistent with the hypoth-
livable world. esis that Ryugu formed from fragments of a
larger asteroid that became well mixed as
TREASURE BOX they coalesced. After it formed, the surface of
The Hayabusa2 asteroid explorer mission Ryugu was weathered by radiation and light
launched on 3 December 2014. Some 1,302 from the Sun, cosmic rays, and collisions
Emily Lakdawalla, using data from JAXA/ISAS (Ryugu, Itokawa) and NASA/JPL/U. Arizona (Bennu)
25143 Itokawa 0.5x0.3x0.2km
days later, the spacecraft arrived at its destina- with micrometeorites. This space weather-
tion. On 27 June 2018, the spacecraft thrusters ing tends to make a surface darker and redder.
fired to maintain a constant position 20 kilo- When loose material slides down the slope of
meters (12 miles) from the asteroid on a line the steep equatorial ridge, the slides expose
between Earth and Ryugu. This is our “home fresher material, offering a likely explanation
position,” where we perform the majority of for the ridge’s bluer hue.
our remote observations. Our instruments The expected collisional history for NEOs
revealed a new world that surprised the meant that we anticipated that Ryugu would
whole team. have a “rubble-pile” structure: rather than
MAKOTO YOSHIKAWA is mission manager for Hayabusa2 at the Japan Aerospace Exploration
Agency (JAXA) Institute of Space and Astronautical Sciences (ISAS). He specializes in celestial
mechanics, particularly orbital analysis of small solar system bodies. He is also interested in the issue
of planetary defense, which concerns potential Earth impacts from celestial bodies. ELIZABETH
TASKER is an associate professor at the Japan Aerospace Exploration Agency (JAXA) Institute of
Space and Astronautical Sciences (ISAS). Her research uses computer models to explore the formation
of planets and galaxies. Her popular science book, The Planet Factory, was published in 2017.
20 T H E P L A N E TA R Y R E P O R T C JUNE SOLSTICE 2019DCAM-3 (Deployable Camera) Contains a digital and an
analog camera, watches SCI operation from a distance
STAR TRACKERS For navigation
NIRS3 (Near Infrared Spectrometer)
For measuring composition
REENTRY CAPSULE For protecting samples
during Earth atmospheric entry at speed of 12 km/s
MINERVA-II-1 Small, solar-powered surface hopper
LIDAR (Laser Altimeter) Laser ranging for measuring 3D
shape of Ryugu; works from 30- to 25,000-meter range
MINERVA-II-2 Small, solar-powered surface hopper MASCOT German-
and French-built
SAMPLE HORN Leads to 3-chambered sample surface hopper with
capsule; fires a tantalum bullet to obtain sample
4 instruments and
17-hour lifetime
ONC-W2 (Optical
HAYABUSA2 Navigation Camera–Wide
INSTRUMENT Angle) Monochrome
cameras for navigation;
INVENTORY 65.24° field of view;
10241024 pixels;
1 mrad/pixel.
TARGET MARKERS Soft balls covered with reflective ONC-T ONC-W2 angled 30°
material to guide Hayabusa2 to touchdown point (Optical
Navigation ONC-W1 (Optical
SCI (Small Carry-on Impactor) Uses explosives to accelerate Navigation Camera–Wide
a 2-kg copper bullet into Ryugu to make a crater Camera–
Telescopic) Angle) Monochrome
TIR (Thermal Infrared Imager) For measuring surface temperature Color camera cameras for navigation;
CAM-H (Small Monitoring Camera) Color camera for for navigation 65.24° field of view;
viewing sample horn; paid for by public donations and mapping; 10241024 pixels;
6.35° field 1 mrad/pixel.
of view; ONC-W1 points
10241024 straight down
pixels; 0.1074
mrad/pixel
a coherent body, it’s made of rocks held subsurface material. The spacecraft itself also
loosely together by the asteroid’s gravity. needed to touch the surface to gather material.
We had expected to see a surface pitted with After almost 2 months of remote observations,
craters and boulders, interspersed with flatter the Japanese and international team members of
regions and covered with a layer of finer-grained the Hayabusa2 Joint Science Team gathered at
regolith. However, we were shocked to find that ISAS to choose landing sites. Data from optical
Ryugu appears to have almost no fine-grained navigation cameras and a laser altimeter had ABOVE The Hayabusa2
regolith. A global look at Ryugu shows a homo- been used to create a 3-dimensional model of mission is examining
geneous spread of boulders larger than 8 meters, the asteroid to guide the selection. Consider- Ryugu using remote-
sensing instruments,
while closer inspection reveals a high density ations such as surface temperature, local slope,
rovers, and a lander, with
of boulders about 1 meter in size. The largest and boulder density were major factors for the an impact experiment
Emily Lakdawalla, Charles H. Braden, and Loren A. Roberts for The Planetary Society
boulder, 130 meters across and named Otohime landing site selections, which also had to be safely to expose a sample of
Saxum, sits near the south pole. separated in distance so as not to interfere with subsurface material to
Itokawa (the destination of Hayabusa) also one another. carry back to Earth.
had a surface covered in boulders. However, this The day of intense discussion resulted in
OPPOSITE PAGE Hayabusa2’s
asteroid had a flat plain with a width of about choosing sites on the asteroid’s northern side for
target asteroid, Ryugu, is
50 meters covered with approximately centi- the rovers, the southern side for the lander, and very small but still larger
meter-sized grains of regolith. We had expected close to the equator for touchdown. The sites were than OSIRIS-REx’s Bennu
a similar open space on Ryugu, and its absence also separated in longitude around the asteroid. and Hayabusa’s Itokawa. All
made landing a serious challenge. About a month later on 21 September, have boulder-rich surfaces,
but Ryugu and Bennu
Hayabusa2 descended to a low altitude of about
have less dust and fine
ROVING AN ASTEROID 55 meters over Ryugu’s surface and separated 2 gravel than Itokawa. Each
Hayabusa2 has 4 different types of surface opera- of the rovers, MINERVA-II-1A and -1B, later named closeup is 60 meters wide.
tions. The spacecraft carried 3 rovers, a Euro- HIBOU and OWL. They were designed to test
pean-built lander, and a Small Carry-on Impactor motion in a low-gravity environment. On Ryugu,
(SCI) for generating an artificial crater to expose there is not enough friction for wheels to roll.
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