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"I'm Mike Brown, and I'm a professor of planetary astronomy at Caltech. I study anything you
can do in the solar system with telescopes, mostly the outer solar system."
Why Europa?
"I find Europa one of the most fun bodies in the solar system, mostly because if you
were just looking around the solar system looking for an object that was interesting
in some way, interesting in the sense that it has a lot of liquid water. You would look
at the Earth and say, yep, a lot of water there, that's pretty cool. The next place
you would look is Europa - it has the most amount of liquid water of anywhere in the
solar system. So it has to be an interesting place, simply by virtue of having that much
liquid water. And one of the things I'm most interested in is trying to understand what
else is in that ocean besides the water. What is the chemical composition of the salts in
that ocean? An understanding the composition leads you to understand things like if the
conditions are the types of conditions that might be conducive to life. I'm not going
to say that they tell you if there is life or not, but they are the sorts of things that
can tell you that it's chemically rich that life might enjoy or if it's kind of a sterile
environment. And we've been learning about the composition of the ocean by looking at
the surface of Europa where, in cracks or geysers or some way the ocean gets onto the
surface and evaporates, and the salts get out on the surface, and we study those salts
to tell what's there."
How do we get under the ice?
Exploring underneath the ice of Europa is hard, but one of the nice early steps would
be that you can just land on the surface and the surface has stuff from the ocean, so you
can just scrape it off the surface and take a taste of it and see what the ocean is like.
But if you really want to get down below and swim around in the ocean and explore, and
who wouldn't? In the proposed missions that I've heard, and in the only one that seems
semi-viable, you land on the surface with basically a big nuclear pile, and you melt
your way down through the ice and eventually you get down into the water. Then you set
your robotic submarine free and it goes around and swims with the big Europa whales."
Is there a specific chemical they should be looking for?
It's hard to imagine that you could find anything even a chemical signature inside the ocean
that would really push the idea that there must life under there making it happen, and
the reason that it would be hard to find something that would make it so obvious is that we know
so little about the core composition of Europa and it's interaction sea water. And many different
things could be going on to cause all sorts of disequilibrium chemistry, and that's sort
of what you're always looking for - chemical species that shouldn't be there if everything
was just in regular equilibrium. And there's so many reasons that you might have it on
Europa - you have interactions with the core, a strong radiation environment - that it would
be very difficult, I think, to come up with a really sound chemical fingerprint that life
must exist there."