When we think of liquid water among Saturn’s moons, the first thing that comes to mind
is Enceladus where not only is there a huge volume of liquid water locked under a shell
of ice, that water bursts through into space like a geyser and allows for direct study
of the composition of the water beneath.
As covered in previous videos, we now know that water is nutrient rich, and suggests
the presence of geothermal vents.
Unfortunately, models indicate that Enceladus is not that old of an object, having formed
as recently as 100 million years ago.
This is a count against life existing in those waters as it may not yet have had enough time
to arise, but it doesn’t knock the possibility out, the chemistry of life can happen very
quickly and there’s always panspermia.
But Enceladus ultimately may end up being a place where life may arise in the future,
as opposed to a body where it already exists.
Perhaps some day it might be the laboratory where we passively observe the genesis of
life unfolding in real time.
And let’s not forget Jupiter’s moon Europa, unlike Enceladus, is billions of years old
and life has had plenty of time to get started there.
But that does not mean that the Saturn system itself is lifeless.
There are two other moons that are thought to have similar oceans locked under shells
of ice.
The first of these is Titan, which is old, having formed at or shortly after the formation
of Saturn early in the solar system’s history.
Titan is a strange moon as far as life goes.
It’s one body in the solar system where life as we do not know it may be possible,
along with the possibility of more conventional earth-like life in the water ocean below.
In other words, there are two chances for life on this moon.
Plus, there are clear indications on this moon of lots of prebiotic organic chemistry
going on, a precursor for the formation of life.
The first chance with Titan is on its surface.
The surface of Titan is the only other place in the solar system where liquids currently
flow and form something much like earth’s water cycle.
But water is basically a rock on the surface of Titan due to extremely low temperatures.
Instead the liquids are hydrocarbons, and there are hypothetical ways for life to exist
using liquid hydrocarbons as a solvent at low temperatures.
Whether life like this can really exist is open to debate.
But there have been tantalizing hints of something going on on the surface of Titan.
For example there are indications that hydrogen molecules flowing downward from the upper
atmosphere inexplicably disappear near the surface.
Another is a lack of acetylene.
It’s possible that they are being consumed by exotic methane-based microbes, but it’s
not a smoking gun and natural abiotic processes haven’t been ruled out.
The second chance for life at Titan is in its liquid water ocean that lies under the
surface.
Not much is known about this ocean other than it seems to have extremely high density based
on data from the Cassini spacecraft.
This could suggest that it’s really salty, something like the Dead Sea here on earth,
or worse.
But the Dead Sea gets a bad wrap, since it’s far from dead.
It is in fact an abode of microbial life and there are a whole class of microorganisms
termed Halophiles, named so because they love salt and they die if you put them in fresh
water.
So being really salty does not preclude the possibility of life residing in the subsurface
oceans of Titan.
And there’s also ammonia, the ocean is thought to be more of a mix of water and ammonia than
purely water.
But ammonia itself has been proposed as an alternative solvent for life to arise in,
much like the surface liquid hydrocarbons.
But, while all of this is tantalizing, the best way to answer the question is to go study
Titan directly.
And while Titan may represent the best chance in the Saturn system for life followed by
Enceladus, there is actually a third body in orbit of Saturn that seems to harbor a
liquid water ocean.
It’s the moon Dione and data taken by the Cassini mission suggests a liquid water ocean
lurks under a shell of ice, much like Enceladus and Europa, and in fact quite a few other
moons.
Not much is known yet about this particular ocean, though there is some geologic evidence
on the surface that is best explained by the presence of an ocean.
And there’s a fourth option for Saturn, though we know almost nothing about this one
other than some models suggest that radioactive decay could allow for liquid water beneath
the surface.
It’s the moon Rhea, and water there remains speculative.
But it also wouldn’t be surprising, ice shell water moons seem to be common in the
universe if our solar system is any indicator.
Liquid water, of course, favors life.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently envisioning an Enceladus
scenario where we get there only to find out that it’s been contaminated by Europa life
through panspermia, Europa ruins everything and be sure to check out my books at your
favorite online book retailer and subscribe to my channel for regular, in-depth explorations
of the interesting, weird and unknown aspects of this amazing universe in which we live.