Death Star and Pac-Man: The Mysterious Mimas

The resemblance to the “Death Star” is imparted to Mimas by a huge notch - the Herschel crater, whose diameter is 139 km, despite the fact that the satellite itself is only 396 km in diameter

An unexpected and very strange distribution of daytime temperature is found on the surface of Mimas

A slight difference in surface color is easily visible in this image taken by the Cassini probe during the closest flight from the satellite

Dark stripes are seen running down the slopes of some craters in that part of Mimas, which is oriented forward, in the direction of its rotation around Saturn

After processing the data from the Cassini probe operating in the vicinity of Saturn, scientists compiled the most detailed map of the surface temperature of Mimas at the moment. This picture looks very strange: it seems as if the "Death Star" from the cult movie saga is being devoured by "Pakman" from an equally iconic computer game. These data were received by Cassini on February 13, when it flew at the closest possible distance from the satellite, and it is still not possible to fully explain them. From a rather boring place, Mimas suddenly became a rather intriguing object of research.

The fact is that scientists predicted that here the temperature should vary gently, reaching a maximum during the day, near the equator. It turned out that the hottest region of the satellite seemed to be spread out at its visible edge, and it warms up as much as possible in the early morning. Here the temperature rises to about 92 Kelvin, while in the rest of Mimas it does not exceed 77 Kelvin. Another small, relatively warm area is located around the Herschel crater, where the temperature reaches about 84 Kelvin (take a look at the illustration on the left).

There were no special problems with this “warm place” near the crater: its high walls, reaching 5 km, are quite capable of retaining heat. But what about the “Pakman, ” a strange V-shaped “hot” region?

Scientists suspect that its appearance is associated with a difference in surface texture. For example, denser ice can quickly absorb heat and transfer it deeper, keeping the surface cold for a whole local day. In contrast, loose ice on the surface retains heat in place. But then it will be necessary to explain why such sharp boundaries between regions with different temperatures are connected. In other words, why are different forms of ice distributed over the surface of Mimasa in distinct, non-mixing deposits?

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In addition, on the slopes of some craters, which are located in the “front” hemisphere of the satellite, directed towards its orbiting around Saturn, dark stripes are seen, as if something flowed down in them. Perhaps this is due to the fact that over time, the Mimas surface accumulates a thin layer of minerals - for example, as a result of meteorite bombardment, or meeting with cosmic dust, or the structural features of the satellite itself.

Little by little, under the influence of sunlight, brighter ice evaporates, and dark minerals are concentrated. Gravity causes these deposits to slowly but surely descend down the slopes of the craters - where these deposits appeared.

Other interesting details about Mimas, Saturn and their neighbors can be found in our article “Rings and Arches”.

By NASA JPL Press Release

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