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Mimas and see - summary of new findings

The Herschel Crater in Mimas and the surprising atmosphere of Ra are just some of Cassini's discoveries in the Saturn system 


Mimas and the Herschel Crater on it. Taken by the Cassini spacecraft on February 13, 2010
Mimas and the Herschel Crater on it. Taken by the Cassini spacecraft on February 13, 2010

On February 13.2.2010, 9500, Cassini made the closest flyby of this moon. She passed at a distance of 1 km from him (XNUMX). The new photographs show that the floor of the Herschel crater was probably filled with igneous material that erupted from the interior of the moon when the crater was formed. At the western end of the crater floor there is a tongue of material that is higher than the surface and appears to be close to the rim of the crater. It shouldn't be there because the moon's gravity would have pulled it down, the shape of the tongue can indicate the rapid freezing of the trend that stuck it to the crater wall, or the presence of a substance that stuck it to the wall. There are small malls on the floor of the crater. There was tectonic activity in the place, in a later period.


There are also craters inside the Herschel Crater, but their density is lower than that of the craters outside it. The crater-forming body threw up rock fragments including ice blocks. The fall of these created secondary craters (2).

In some of the craters in the vicinity of the Herschel crater you can see that their sides are light and that their floor is 20% darker than the sides (2). In other craters there are dark stripes along the inner sides. It may be a concentration of substances (impurities) that remained during the evaporation of the ice (3).

When the temperatures of the moon were measured it was found that part of its surface is hot and part is colder. A band in the shape of the letter V was found whose temperature is -181 C. The temperature of the rest of the surface is -196 C. The reason for the cold zone is probably due to the fact that the ground has a higher heat conductivity and the sun's heat is drawn in below the surface. The Herschel crater is also hotter than its surroundings, although to a lesser extent than the V formation (4).


On 9.2009 and 3.2010, Cassini passed at a distance of 100 km from the moon and on 11.1.2011 it passed at a distance of 76 km from it. These were the closest passes to this moon to date and they produced a series of very high resolution photographs that allowed a probing view of the surface. So far, 4386 photographs of See What You Can Prepare for a detailed atlas have been broadcast to Israel. The resolution range ranges from 6.5-500 meters per pixel. For the purpose of mapping, the 370 photographs with the highest resolution were selected (5,6).

Contrary to what was thought following previous observations, it turned out that the moon does not have its own rings. The assessment based on which they came to the conclusion that rings exist was based on a symmetrical decrease on both sides of the moon in the amount of electrons. To test this, it was decided to observe the moon in a view where both sides of the moon are visible from end to end. For this purpose, 65 photographs taken between 2008-2009 were examined. Some are at a high angle relative to the dark side of the moon and some are at a low angle relative to its light side. The photographs from the dark side are designed to see microscopic particles that refract the light forward and those taken from the light side are designed to see large bodies absorbing light and returning it to the sun. A short exposure of the cameras to light was also used. No particles that are supposed to form the ring have been found. What caused that decrease in the amount of electrons remains an unsolved puzzle (7).
Surprisingly, it turned out that Lerah, despite its small dimensions, has its own atmosphere. The main component is oxygen and the second component, although in a much smaller amount, is CO2. The amount of oxygen is 50 billion molecules per cubic meter and of CO2 20 billion molecules per cubic meter. The density of the atmosphere is 100 times greater than the ecosphere of the Earth's moon and that of Mercury. The source of the oxygen is from the chemical decomposition of the water ice by the radiation of Saturn's magnetosphere and the source of the CO2 is probably in reactions between oxidizers and organic substances. Another possibility is its release from dry ice that was trapped in the ground during the time when the solar system was formed, as in the case of comets. Another possibility is carbon-rich materials deposited in the ground by small meteorites (8,9).

ground colors

In a narrow strip 10 km wide that surrounds the equator there are blue spots. Their distribution is uneven and they are found on the inner walls of craters. It may be fresh ice exposed to the surface. What is interesting is that this color is not found at the bottom of the craters themselves (10,11).


In the high-resolution photos, you can see the terrain in the most detail. In photo 12742PIA located at W°235 S°17 a crater can be seen whose half has undergone weathering. The wall has been completely removed and in a crater near it small canyons can be seen on one of its sides, which indicates local tectonics (12). In another photo you see canyons cutting a crater, evidence of more extensive tectonics (13). In one of the most interesting craters made from a distance of 76 km from the moon, there is a prominent formation that looks like a volcano, which can indicate volcanic activity (14). In another crater you see a ground subsidence and the central bulge is unusual in its appearance. A kind of sequence of two relief columns. The configuration is not entirely clear, but in any case it stands out in its abnormality (15). In another photo you can see a column of secondary craters exiting a large crater (16).


In photo 12807PIA located W ° 273 N ° 12 you see 3 wide canyons that are 4 km deep. One of them becomes narrow where it cuts a crater and enters it (17). In another photograph, you can see shopping malls with an undulating configuration (18). In other photographs, such as on the moon, formations reminiscent of straw (wispy marking) are discussed. In high-resolution photographs it became clear that these are exposed areas of ice along the length of slopes, grooves and rock lines that indicate tectonic activity. In one of the series of photographs one sees cracks that cut the surface sometimes at right angles to each other (19).

stripe configuration

In one of the photographs you see bright stripes that are hundreds of kilometers long and two of them cross each other (20). A similar phenomenon is found on the moon Dion (21).


1. "Cassini set to do retinal scan of Saturian Eyeball" 17.2.2010 Cassini _Set_ To_ Do_ Retinal_ Scan _Of_ Saturian_ Eyeball_999.html

2. PIA12568: Examining Herschel Crater PIA12568

3. PIA12571: streaked craters in false color PIA12571

4. PIA12867: Bizarre temperature on Mimas PIA12867

5. "DLR researches compile atlas of Saturn's moon Rhea, an icy alien world" 22.12. 2010 Researches _Compile _Atlas _Of_ Saturn’s_ Moon_ Rhea_ An_ Icy _Alien_ World_999.html

6. PIA12806: The Rhea Atlas PIA12806

7. Gold L.- "No rings around Saturn's Rhea" 2.8.2010 Rings _Around_ Saturn’s _Rhea_999.html

8. Atkinson N. – “Tenuous Oxygen atmosphere found around Saturn's moon Rhea” 26.11.2010 -oxygen- atmosphere- found -around- moon- rhea/#more80237

9. "Cassini finds ethereal atmosphere at Rhea" 28.11.2010 Finds _Ethereal _Atmosphere_ At _Rhea_999.html

10. PIA12854: Rhea's blue streaks (looking south) PIA12854

11. PIA12855: Rhea's blue streaks (looking west) PIA12855

12. PIA12742: Superimposed craters PIA12742

13. Image N00146890.jpg

14. Image W000273.jpg

15. PIA12746: Rhea's northern craters PIA12746

16. Image N0066780.jpg

17. PIA12807: Rhea's fractured terrain in 3-D PIA12807

18. PIA12809: Rhea's western wisps PIA12809

19. "Cassini marks holidays with dramatic views of Rhea" 22.10.2010 Marks_ Holidays_ With_ Dramatic_ Views_ Of_ Rhea_999.html

20. Image N00166885.jpg

21. Image N00041190.jpg

2 תגובות

  1. The amount of oxygen in the Earth's atmosphere is approximately 10^25 molecules per cubic meter, which is a 1 followed by 25 zeros.
    The amount of carbon dioxide in the Earth's atmosphere is approximately 10^20 molecules per cubic meter.

  2. "The amount of oxygen is 50 billion molecules per cubic meter and of CO2 20 billion molecules per cubic meter"

    For comparison, what are the figures on Earth

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