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Enceladus is one of Saturn’s many moons, and it’s a very small moon
that people tend to kind of ignore because it is so small
about 500 kilometers in diameter.
But decades ago, in the 1980's from ground-based observing,
we found out that the location of Enceladus relative to Saturn
happened to coincide nicely with Saturn’s E ring
and so we were thinking that Enceladus had something to do with the E ring
particulates, that icy material, but we weren’t sure.
What we later find from Cassini was that we directly determined
that there are indeed plumes jetting out of the south polar region from cracks
in the south pole of Enceladus in the crust.
And it’s dominantly water-rich material just jetting out into space.
And so the way we saw it, Cassini happened to be located where Enceladus was backlit
from the Sun, and so you saw this curtain of beautiful, diffuse material
jetting out of the south polar region – quite breathtaking actually.
Even more, we were able to use the different compliments of instruments
onboard Cassini to go after the chemical composition of the plumes,
and that’s where things got really interesting. So number one, that’s because of liquid water.
There’s definitely a liquid water reservoir subsurface below the icy crust, but that is there.
Number two, the chemical composition of the plumes told us that there is a lot of organics
things that make up amino acids and things on life that are very interesting.
And number three, what we were really looking for was a source of energy.
On Enceladus, photons from the Sun aren’t going to work because you can’t penetrate
the tens of kilometers of icy crust to get down to where the liquid water reservoir is.
But, what Enceladus does have is hydrothermal vents.
It’s very hot with the liquid water, that has a lot of analogies with the ocean floor
where we have a form of releasing chemical energy via something called serpentinization.
And so we think that Enceladus might have that potential
to have an energy source being chemical, not sunlight.
And so you put all that together and Enceladus has all the ingredients,
or most of what we need for life.
That makes it a very astrobiologically interesting object to study.
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