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A lander on Jupiter's icy moon Europa may have to dig at least 1 foot
down to find signs of life
By Mike Wall 8 days ago

Jupiter's ocean moon Europa, as seen by NASA's Galileo probe.

Robots may have to dig relatively deep on Jupiter's icy moon Europa to
have a shot of finding signs of life, a new study suggests.

Scientists think Europa harbors a huge ocean of liquid water beneath its
icy shell. This ocean appears to be in contact with the 1,940-mile-wide
(3,100 kilometers) moon's rocky core, making possible a range of complex
chemical reactions. As a result, Europa is generally regarded as one of
the solar system's best bets to harbor alien life.

If life has ever existed on Europa, some signs of it may bubble out of
that buried ocean onto the surface, where robots could potentially spot
it. Well, not right on the surface; Europa gets hammered hard by charged
particles, which are trapped and accelerated by Jupiter's powerful
magnetic field.

Photos: Europa, mysterious icy moon of Jupiter

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Previous work has suggested that just 8 inches (20 centimeters) of ice
could likely shield any biomolecules that might exist on Europa from
that punishing radiation environment, even in the hardest-hit regions of
the moon.

The new study, which was published Monday (July 12) in the journal
Nature Astronomy, is a bit more pessimistic. In it, researchers modeled
how Europa's surface is distubed by small but frequent impacts — a real
issue for a world without a substantial atmosphere to burn up incoming
hunks of rock and ice.

They found that such "impact gardening" likely churns the top 12 inches
(30 cm) or so of Europan ice significantly, bringing previously buried
bits up to the surface, where radiation can zap any interesting
molecules into unrecognizable goo.

"If we hope to find pristine, chemical biosignatures, we will have to
look below the zone where impacts have been gardening," study lead
author Emily Costello, a planetary research scientist at the University
of Hawaii at Manoa, said in a statement. "Chemical biosignatures in
areas shallower than that zone may have been exposed to destructive
radiation."

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The new work is likely of interest to NASA, which plans to launch a
Europa spacecraft in 2024. The mission, called Europa Clipper, will
orbit Jupiter but study the moon and its buried ocean over dozens of
close flybys.

Clipper's many duties also include scouting out potential touchdown
sites for a life-hunting lander — a mission that Congress has directed
the agency to mount but which remains a concept for now.

Mike Wall is the author of "Out There" (Grand Central Publishing, 2018;
illustrated by Karl Tate), a book about the search for alien life.
Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom
or Facebook.

Mike Wall
SPACE.COM SENIOR SPACE WRITER — Michael has been writing for Space.com
since 2010. His book about the search for alien life, "Out There," was
published on Nov. 13, 2018. Before becoming a science writer, Michael
worked as a herpetologist and wildlife biologist. He has a Ph.D. in
evolutionary biology from the University of Sydney, Australia, a
bachelor's degree from the University of Arizona, and a graduate
certificate in science writing from the University of California, Santa
Cruz. To find out what his latest project is, you can follow Michael on
Twitter.
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