Saturn's 'Death Star' moon may have a secret ocean, new category that could host alien life

from
https://www.businessinsider.com/saturns-death-star-moon-mimas-may-have-a-secret-ocean-2022-1

Saturn's 'Death Star' moon may have a secret ocean, revealing a new 
category of worlds that could host alien life
Morgan McFall-Johnsen 20 hours ago

mimas moon round grey rock with large crater
NASA's Cassini spacecraft took the most detailed photo to date of Mimas 
on its closest flyby of the Saturn moon in 2010. NASA/JPL-Caltech/Space 
Science Institute
Saturn's small moon Mimas could have an ocean of liquid water deep 
beneath its surface.
NASA's Cassini spacecraft detected swaying in the icy moon's spin that 
could lead to internal heat.
Mimas appears inactive on the surface, so an ocean there could mean a 
new class of "stealth" ocean worlds.

NASA is studying several moons of Saturn and Jupiter that carry oceans 
of liquid water deep beneath their surfaces, where alien life could 
thrive. Another moon, previously assumed to be a barren ice rock, might 
join their ranks.

Mimas is a small moon of Saturn, often compared to the Death Star from 
Star Wars, thanks to its large, distinct crater. Scientists have long 
believed that Mimas is an inert ball of ice because of its heavily 
cratered surface. Icy worlds with oceans are usually smooth, since 
changes in their surface ice pave over craters, or cracked. Tidal forces 
stretch and relax these moons, which both cracks the surface ice and 
heats the moons' insides, sustaining internal oceans.

But NASA's Cassini mission, which orbited and studied Saturn for over a 
decade, detected an unexpected oscillation in Mimas's rotation. As it 
spins on its axis, Mimas wobbles slightly. Such oscillations may point 
to an ocean deep beneath the moon's ice, according to a new analysis.

saturn rings up close with distant moon mimas in the background
Mimas orbiting Saturn beyond the planet's rings, pictured by NASA's 
Cassini spacecraft in 2008. NASA/JPL/Space Science Institute
"If Mimas has an ocean, it represents a new class of small, 'stealth' 
ocean worlds with surfaces that do not betray the ocean's existence," 
Alyssa Rhoden, a geophysicist who led the analysis at the Southwest 
Research Institute, said in a press release.

Rhoden's finding was published online in the journal Icarus this week, 
in a paper co-authored with Matthew Walker of the Planetary Science 
Institute in Arizona.

It's still no guarantee of a secret Mimas ocean. Researchers need to 
investigate the moon for further evidence.

"The work doesn't prove that there is a subsurface ocean on Mimas, but 
it does show that an ocean is perfectly consistent with the available 
data and our understanding of the physics, and the authors are 
appropriately cautious about this," Michael Bland, a space scientist who 
studies icy worlds at the US Geological Survey, and previously spoke 
with Rhoden about the research, told Insider in an email. "I think the 
study also opens as many questions as it answers."

Underground oceans on distant moons could mean alien life in our solar 
system
illustration underwater robot studying deep-sea vents in alien ocean
An illustration of a submersible robot exploring the subsurface ocean of 
an icy moon. NASA/JPL-Caltech
Mimas's oscillation could indicate that Saturn's gravity stretches and 
relaxes the planet as it spins — similar to the moon's gravity pulling 
Earth's water back and forth during tides. This process could build up 
energy deep inside Mimas, which is released as heat, warming its 
internal ice and creating an underground ocean of liquid water.

Rhoden and Walker developed computer models to simulate that stretching 
process for Mimas, including how it would affect the stability of the 
moon's ice shell, and how that stretching fits in with Cassini's 
measurements of Mimas's oscillation. The model indicated that Saturn's 
tidal pull could maintain an ocean lying beneath 14 to 20 miles of ice 
on Mimas.

"This result is really intriguing because it implies that we can't tell 
which moons in the outer solar system may have subsurface oceans just 
from their surface geology," Bland said.

Some moons — like Jupiter's Europa and Saturn's Enceladus — have plumes 
of water shooting up from their internal oceans, through their surface 
ice, and into space. In 2020, scientists also discovered evidence of an 
underground ocean on a dwarf planet called Ceres, which orbits the sun 
between Mars and Jupiter. Salt deposits on Ceres's surface appear to 
have percolated up from liquid water below.

These ocean worlds could have deep-sea hydrothermal vents that produce 
energy for living organisms. Such vents serve as an energy source for 
life at the bottom Earth's oceans, where there is no sunlight. If Mimas 
has an ocean, it might be able to host such ecosystems, too.

hydrothermal vent noaa oar nurp
A hydrothermal vent on Earth. OAR/National Undersea Research Program 
(NURP); NOAA

But the study isn't enough evidence to prove that. If the researchers' 
models are off — if Mimas's ice cools faster than they assumed, for 
example — there may be no Mimas ocean at all.

"If the Cassini spacecraft had been able to fly closer to Mimas, it 
might have sensed a magnetic field generated by the Mimas ocean, which 
would be a direct confirmation that an ocean is present today," Steve 
Vance, who studies icy worlds at NASA's Jet Propulsion Laboratory, told 
Insider in an email. "Hopefully a future mission will be able to look 
for an ocean in Mimas."

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