Recent decades have seen a revolution in planetary science when considering just where life in
our solar system or the universe at large might arise.
We know that life can arise on a clement, relatively stable planet like Earth, but from
life on earth we know that life is tenacious, sometimes absurdly so, and simple forms of
life may arise on worlds that aren’t so earth-like or anywhere close to it.
Studies of the moons of our solar system have shown us that liquid water can exist under
the right conditions on worlds outside the habitable zones of their star.
Europa and Enceladus stand out here, both having deep liquid water oceans beneath crusts
of ice, as does Mars which might have briny liquid flowing through aquifers protected
from the harsh conditions of its surface.
But we also know that both Mars and Venus once had extensive liquid water long enough
for life to develop in the same grain as earth.
But these planets and moons are not the only places where liquid water beneath the surface
of a world within the solar system might exist.
The liquid water list is frankly growing extensive.
There is some evidence of a liquid water ocean of some type at Jupiter’s moon Ganymede.
It may also be possible at wildly volcanic Io, see my video on this channel for more
on that possibility.
And to complete the set of the Galilean moons, even Callisto may have liquid water deep beneath
its ice shell.
There are other places that have been advanced as possibly having liquid water, such as Titan
and even Pluto.
I suspect this list of possible candidates for subsurface liquid water in the solar system
is only going to grow in the future.
But one candidate stands out in that while it is classed as a minor planet, it’s really
part of the asteroid belt leading to much confusion on just what to call it.
It’s Ceres, the largest object in the asteroid belt and whether it’s a planet or an asteroid,
it has a really unusual mix of characteristics that may point to it being or once having
been an abode for microbial life.
And, given its position in the asteroid belt, if it did have life it would be a candidate
for possible panspermia, seeding that life to other worlds in the solar system when undergoing
impacts, possibly even to our own planet.
Before the Dawn spacecraft visited it, Ceres was largely expected to be a dead world, just
the largest of a group of rocks.
But as often happens with space exploration, it surprised us.
There was evidence of recent resurfacing at Ceres along with abundant water ice.
This implies that some kind of liquid water persists in the interior, though to what extent
isn’t known, and it probably isn’t prudent to call it an ocean.
The liquid probably isn’t as extensive as with other worlds in the solar system.
But if it does exist it would probably have to be salty or maybe mixed with ammonia or
another chemical that can keep it from freezing.
But that wasn’t the only thing Dawn discovered at Ceres.
It also spotted evidence of organics on the surface.
You don’t need life for organics, indeed organic chemistry seems to be everywhere in
the universe, but you do need organics for our kind of life.
Liquid water and organics together hold the potential for life.
And in that past, the water at Ceres may have been more extensive.
In a 2010 presentation by J.C. Castillo-Rogez and P.G.
Conrad of JPL they detail that observations of Ceres reveal the presence of minerals on
the surface of Ceres that indicate hydrothermal activity in the past, perhaps even at or close
to the surface.
If that state of affairs persisted long enough for life to arise, then it may have adapted
and might still persist deep below the surface of Ceres or may have even been transported
by meteorite to other bodies in the solar system’s history, and perhaps even to earth.
Thanks for listening!
I am futurist and science fiction author John Michael Godier and be sure to check out my
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explorations into the interesting, weird and unknown aspects of this amazing universe in
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