ANTARIKSA – In early 2024, researchers discovered that a large liquid ocean was hiding under the ice cover of Saturn’s small moon, Mimas. Now, the same team is back with research results on how the ocean got there.
The new research, published in the journal Planetary Science Letters, shows that when Mimas’ orbit around Saturn flattens due to the ringed planet’s gravitational pull, its icy shells melt and getting thinner. This created huge oceans that started between 2 million and 25 million years ago. For features in the solar system, the age of Mimas’ subsurface ocean is relatively young.
In fact, the discovery of a very small ocean in Mimas has redefined the existence of subsurface oceans in the solar system. “In previous research, we discovered that for Mimas to be the ocean world today, it must have had a much thicker ice shell in the past. “However, since the visibility of Mimas was much higher in the past, the path from thick ice to thinner ice became complicated,” said the leader of the research team and Senior Scientist at the Institute of Planetary Science, Matthew E Walker in commentary.
A small moon with a wide ocean
Mimas is the nickname of the Death Star because it has the Herschel crater, which makes it look like the Imperial space station in Star Wars. The crater was created when Mimas collided with another celestial body around 4.1 billion years ago.
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Mimas is only about 400 kilometers in diameter, so it is very small compared to the diameter of our Moon on Earth, which is 3,475 kilometers. However, Mimas has a large ocean 20 to 30 kilometers below the surface of its icy crust.
Mimas’ outer hydrosphere, which consists of ice and water, is estimated to be 70 kilometers deep, and its oceans are 40 to 45 kilometers deep. This means that the ocean appears to make up half the size of Mimas.
Walker said the research had shed new light on the tidal processes that could have created these great oceans. This happens when it is distorted or stretched due to changes in gravitational forces in an elliptical orbit.
“Instability drives tidal heating, and we think that’s the cause of the heat that’s causing the current thinning of the Mimas ice sheet,” Walker said.
Walker said tidal heating is not free energy. This means that when Mimas’ shell melts, tidal heating will draw energy from the moon’s orbit around Saturn. This will further reduce the complexity of the orbit until finally Mimas’ orbit is circular, and to stop tidal heating forever.
Read also: Scientists Find Signs of Oceans on Two Solar System Dwarf Planets, Eris and Makemake
Orbital isolation is measured in values from 0 to 1, with 0 representing a perfect circle and 1 representing a parabola. Any value between these numbers is an ellipse. The research team estimates that the beginning of ice melting will begin when the edge in the Mimas orbit is about two or three times the current value.
It is believed that that time happened in the last 10 million years of Mimas’ history, when the moon grew steadily to the geologists see today. “In general, when we think about ocean worlds, we don’t see many craters because surface evolution erases them, like on the moon Europa or the south pole of Enceladus,” Walker said.
2024-04-18 01:53:43
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