A lander on Jupiter's icy moon Europa may have to dig at least 1 foot down

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https://www.space.com/jupiter-moon-europa-alien-life-dig-deep

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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