Mimas Ocean … Or Lake

More than a decade ago, I suggested that Saturn’s moon Mimas was a candidate for interior water. My hypothesis was that the farther a moon’s orbit varied from perfect circularity, the likelier astronomers were to find water sloshing around the interior. Other factors would be nearby moons to generate tides, not to mention the large planet.

Seems like my guess might be true.

(Mimas’) orbit around Saturn is highly eccentric, meaning it gets tugged and stretched as it swings close to the powerful gravitational force of the planet and then orbits farther away.

It’s not really “highly eccentric.” The variation, by percentage, is the same as the Earth’s orbit around the sun. Our distance to the sun isn’t a standard 93 million miles. In January, we are 91.5 million miles away. By summertime, we are three million miles farther away.

(Alyssa) Rhoden, a principal scientist at the Southwest Research Institute, a science organization, followed up on an earlier observation of a tiny wobble in Mimas’ orbit around Saturn. An icy sea sloshing inside Mimas could potentially trigger this wobble. Might tidal heating have melted enough ice inside Mimas to create a sea? If so, there couldn’t be too much heat (that would melt through the icy shell) nor too little heat (then the ocean would freeze).

The researchers calculated that if there was indeed an ocean inside Mimas large enough to trigger its wobble, the water would exist beneath an icy shell some 14 to 20 miles thick. So they ran computer simulations of how the heating (from tidal heating) would impact the ice on Mimas. Unexpectedly, it showed an ocean under 14 to 20 miles of solid ice.

“We came up with exactly the right number,” Rhoden said.

Wikipedia summarizes the argument against as well as for.

Considering that the world is only 240 miles wide, “ocean” seems a bit of an exaggeration. Small lake, perhaps. Still, it would be interesting to tunnel into this little moon and see what was there to inspire wonder.

Credit for one of my favorite images of Mimas above the northern clouds and ring shadows of Saturn: Public Domain, https://commons.wikimedia.org/w/index.php?curid=524410

About catholicsensibility

Todd lives in Minnesota, serving a Catholic parish as a lay minister.
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