Study explains how Enceladus ejects particles from oceans beneath its surface - February 23 2023, by Holly Ober

Study explains how Enceladus ejects particles
from oceans beneath its surface

February 23 2023, by Holly Ober

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Enceladus, the sixth largest of Saturn’s moons, is known for spraying out tiny icy
silica particles — so many of them that the particles are a key component of the
second outermost ring around Saturn. Scientists have not known how that
happens or how long the process takes. A study led by UCLA scientists shows
that tidal heating in Enceladus’ core creates currents that transport the silica,
which is likely released by deep-sea hydrothermal vents over the course of just a
few months. Credit: NASA

Although it is relatively small, Enceladus—the sixth largest of Saturn's
83 moons—has been considered by astronomers to be one of the more
compelling bodies in our solar system.

Enceladus stands apart from other celestial bodies because of both its
appearance and its behavior. It has the whitest and most reflective
surface that astronomers have yet observed. And it's known for spraying
out tiny icy silica particles—so many of them that the particles are an
important component of the second outermost ring around Saturn, its so-
called E ring.

Enceladus is characterized as an "ocean world," a celestial body with a
substantial volume of liquid water. But unlike oceans on Earth, which
are on the planet's surface, Enceladus' ocean is protected beneath a thick
layer of ice. The ice doesn't trap the ocean completely, though: Some
materials from the watery expanse are released near Enceladus' warmer
south pole from large fractures in the ice known as "tiger stripes."

The silica particles that Enceladus ejects begin their journey at the sea
floor, far beneath the moon's surface—and to date, scientists have not
known how that happens or how long the process takes.

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A new study led by UCLA scientists offers some answers. The research
shows that tidal heating in Enceladus' rocky core creates currents that
transport the silica, which is likely released by deep-sea hydrothermal
vents over the course of just a few months.

The research was published in Communications Earth & Environment.

Ashley Schoenfeld, a UCLA doctoral student in planetary science, led a
group that analyzed data about Enceladus' orbit, ocean and geology that
had been collected by NASA's Cassini spacecraft. The scientists
constructed a theoretical model that could account for the silica's
transport across the ocean.

Enceladus' active geology is fueled by tidal forces as it orbits
Saturn—the moon is tugged and squished by gravity. That deformation
creates friction in both the moon's ice shell and its deep rocky core, The
new model demonstrated that the friction heats the bottom of the ocean
enough to create a current that transports the silica particles toward the
surface.

"Our research shows that these flows are strong enough to pick up
materials from the seafloor and bring them to the ice shell that separates
the ocean from the vacuum of space," Schoenfeld said. "The tiger-stripe
fractures that cut through the ice shell into this subsurface ocean can act
as direct conduits for captured materials to be flung into space.
Enceladus is giving us free samples of what's hidden deep below."

Cassini found substantial amounts of hydrogen gas in the plumes which,
together with the silica, present compelling evidence for hydrothermal
activity at the ocean floor. The theoretical model devised by the UCLA-
led team strengthens that hypothesis by demonstrating a plausible
timeframe for the process, and a convincing mechanism that would
explain why the plumes contain silica. The model also would help

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explain why other materials are transported to the surface, along with the
silica particles.

"Our model provides further support to the idea that convective
turbulence in the ocean efficiently transports vital nutrients from the
seafloor to ice shell," said second author Emily Hawkins, a UCLA
alumna who is now an assistant professor of physics at Loyola
Marymount University.

On Earth, similar deep-sea hydrothermal vents harbor a multitude of
fascinating organisms that feast on minerals the vents release.

In the future, spacecraft could gather more data to enable scientists to
further study the physical and chemical properties of Enceladus'
potential hydrothermal vent systems. To determine whether those vents
could support life, scientists would need to test the plumes for chemical
traces of biological activity, known as biosignatures; the new study
offers some guidance that should aid the search for those biosignatures.

NASA's plans for the next decade include missions that would fly by,
orbit and land on Enceladus to gather more information.The UCLA-led
team plans to develop additional modeling that could help shape plans
for those missions.

 More information: Ashley M. Schoenfeld et al, Particle entrainment
and rotating convection in Enceladus' ocean, Communications Earth &
Environment (2023). DOI: 10.1038/s43247-023-00674-z

Provided by University of California, Los Angeles

Citation: Study explains how Enceladus ejects particles from oceans beneath its surface (2023,

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February 23) retrieved 7 September 2024 from https://phys.org/news/2023-02-enceladus-ejects-
                                   particles-oceans-beneath.html

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