From a detailed analysis of Mimas’s orbital motion based on data from NASA’s Cassini mission, planetary researchers from the Sorbonne, the University of Nantes, Queen Mary University of London, Franche-Comte University, and Jinan University have discovered that the heavily cratered They showed that some ice shells hide recently formed ice shells. (less than 2-3 million years ago) global ocean 20-30 km deep.
The surface of Mimas, like the surfaces of other major Saturn moons that do not have atmospheres, is not pure ice but contains some black impurities. Relatively dark markings appear along the lower part of the walls of the 130km-wide Herschel Crater (the crater's central peak is about the same height as Mount Everest); the impact may have all but destroyed the Moon. there is). some small craters. Scientists interpret the darkening as evidence that the impurities have gradually become concentrated as icy material evaporates in areas where they are slowly sliding down the crater walls. Image credit: NASA / JPL / Space Science Institute.
There is growing evidence that some moons may have oceans beneath their surfaces, but such watery worlds are difficult to detect.
Mimas — Saturn's innermost and smallest (radius = 198.2 km, or 123 miles) regular moon — is an unlikely candidate due to the different nature of its surface compared to other icy moons such as Enceladus .
This theory has been challenged by Sorbonne University researcher Valerie Rainey and others who are evaluating Cassini's observations of small satellites.
Previous research suggests two possibilities inside Mimas. It is either an elongated rocky core or a global ocean.
A new study reveals that the small moon's rotational motion and orbit change due to internal influences.
For the solid-state model to apply, the rock core must be elongated and approximately pancake-shaped, which is inconsistent with observations.
Rather, measurements of Mimas' position suggest that the evolution of its orbit is better explained as influenced by an internal ocean.
The researchers calculate that the ocean lies beneath an ice shell about 20 to 30 kilometers deep.
Their simulations suggest that it appeared between 25 and 2 million years ago.
Therefore, signs of such an underground ocean would not have had time to leave traces on the surface.
This result suggests that recent processes on Mimas may have been common during the early stages of the formation of other ice worlds.
“Mimas was a small moon with a cratered surface and no sign of an ocean hidden beneath,” said co-author Nick Cooper, a researcher at Queen Mary University of London. the doctor said.
“With this discovery, Mimas joins an exclusive club of moons with inland oceans, including Enceladus and Europa, but with a unique difference: its oceans are surprisingly young.”
of study Published in today's magazine Nature.
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V. Rainey other. 2024. A recently formed ocean within Saturn's moon Mimas. Nature 626, 280-282; doi: 10.1038/s41586-023-06975-9
Source: www.sci.news
