Signs of subsurface ocean found on Saturn’s small moon

(ORDO NEWS) — A researcher from the Southwestern Research Institute, USA, set out to prove that Saturn’s tiny moon, closest to the planet, is an inactive ice ball, and instead uncovered compelling evidence for a subsurface liquid ocean on Mimas.

In the final days of NASA‘s Cassini mission, the spacecraft identified a curious libration, or oscillation, that occurs as the moon rotates – often indicating a geologically active body capable of supporting a subsurface ocean.

“If Mimas has an ocean, then it belongs to a new class of small, ‘cloaked’ planets with oceans of liquid water that don’t give away the presence of an ocean,” said Dr. Alyssa Rhoden of the Southwestern Research Institute, an geophysics of icy satellites of planets.

“Because Mimas’s surface is cratered, we thought it was a frozen ‘ice’,” Roden said. – Planets with subsurface liquid oceans, such as Enceladus and Europa, tend to be fissured and show other signs of geological activity.

As it turns out, Mimas is “deceiving” us, and our new understanding has allowed us to significantly expand the definition of a potentially habitable planet in our solar system and beyond.”

Tidal processes dissipate the energy of the orbital and proper rotation of a celestial body, turning it into heat. To match the subsurface structure inferred from the observed libration of Mimas, tidal heating must be large enough to keep the ocean from freezing, but must not melt the thick ice crust.

Using tidal heating models, the team developed numerical methods to offer the most plausible explanation for the steady state of the 20 to 30 km thick ice crust surrounding the liquid ocean.

“Most of the time when we were building these models, we had to ‘tweak’ them to the observations,” Roden said. “And the signs of a subsurface ocean just suddenly popped up in front of us when we looked at the most realistic scenarios with a stable ice crust and close to observed libration.”


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