It was 405 years ago that Galileo Galilee discovered the moons of Jupiter and revolutionized
our understanding of science at the time. No longer were we the Earth the center of
the universe. Europa might have a similar prospect. Europa’s among this family of Galilean
moons: Io, Europa, Ganymede and Callisto. It’s a challenge to explore Europa because
it’s immersed in Jupiter’s giant radiation belts. Jupiter’s magnetic field is enormous,
[it] acts to accelerate particles in the Jupiter system and therefore makes it a challenge
to explore Europa. When you look at Europa it doesn’t look like our moon or most other
natural satellites, it’s not covered it craters and from the scarcity of craters we
can say that the surface of Europa is about 60 million years, so something has repaved
Europa’s surface in the time since dinosaurs roamed the Earth. This is what we think the
interior of Europa is like, a thin skin about 100 kilometers or so think of H20. It was
a magnetometer that told us there’s was an induced, probably, an induced magnetic
field and what could be causing that induced field but a salty liquid water ocean, relatively
close to its surface. As Europa and Io and Enceladus go around their parent planets,
it’s in an eccentric orbit so as they get closer to the parent planet they’re stretched
out and farther away they contract a bit. And Europa is orbiting in three and a half
Earth days, every 85 hours its surface is going up and down by about 30 meters, so that’s,
that flexing is causing heating, frictional heating inside the moon which can maintain
an ocean. It can also cause cracking of the surface, a bizarre array of ridges and bands
and cracks that we think are related to this flexing and kneading of Europa’s surface.
That ocean we believe is in direct contact with the rocky mantle below making it pretty
unique among icy satellites. But one thing we’re really trying to get at in understanding
the potential habitability of this probable ocean, first we want to confirm the ocean,
we want to understand, is there communication between the surface and the interior? Because
on the surface we know there are lots of oxidants made by the irradiation of Europa’s surface
and if those oxidants can get into the ocean, that would be a fantastic fuel for life. Europa
also shows these dark pits and spots which we think are related to convection of its
ice shell. Europa shows some reasons where it looks like the surface has been disrupted.
This kind of looks like an arctic ice flow. The surface has been broken up, disrupted,
large blocks have tilted and rotated in this kind of hummocky nature. So we think there
was almost certainly some component of liquid water to allow these blocks to move about.
There might be lakes below Europa’s surface in the ice shell, in the shallow ice shell,
today. So NASA gave the green light to a Europa mission just this past summer and we’ve
been looking at what we’ve been calling the Europa Clipper concept, NASA to pick the
real name in the coming years; a solar powered mission that would make many, many flybys
of Europa equipped with the types of spectrometers, imagers, et cetera to characterize Europa’s
potential habitably.