Ceres is covered with small, young and countless craters, but no more than 280 kilometers in diameter. For scientists this is a huge mystery, since the dwarf planet should have been hit by several asteroid giant during its 4.5 billion years. Where were all these craters ?, you ask the NASA on its website.
A new study in the journal Nature Communications explores the mystery of the great craters missing Ceres , using data from the spacecraft Dawn NASA , which has been orbiting around the dwarf planet from March 2015.
“We have concluded that a significant population of large craters on Ceres are deleted beyond recognition in geological time scales, which it is possibly the result of the peculiar composition and internal evolution of Ceres “said lead researcher Simone Marchi.
He and his colleagues modeled collisions of other bodies with Ceres since the formation of dwarf planet , and predicted the number of large craters that should be present on its surface. These models predicted that Ceres should be between 10 and 15 craters exceeding 400 kilometers in diameter, and at least 40 craters measuring more than 100 kilometers wide. However, Dawn has shown that Ceres only 16 largest craters exceeding 100 kilometers and none exceeding 285 kilometers.
An idea about the origins of Ceres holds that solar system formed far from the , perhaps near Neptune , but migrated to its current location, between Mars and Jupiter . However, scientists determined that even if Ceres migrated to the main asteroid belt relatively late in the history of the solar system, you should still have a significant amount of large craters.
“Whatever the process, the deletion of these craters must have occurred for several hundred million years,” said Marchi according to NASA .
The images of Dawn on Ceres reveal that the dwarf planet has at least three major depressions called ‘planitiae’ They are having about 800 kilometers wide. These planitiae have craters on them that have formed in recent years and the great depressions could be traces of major impacts. One of these, called Harvest Planitia , an area just north of the crater in Kerwan, the largest impact basin better defined Ceres . It is believed that Harvest Planitia must have formed much earlier than Kerwan .
One of the reasons for the lack of large craters may also be related to the internal structure of Ceres . There is evidence obtained by Dawn that the upper layers of Ceres contain ice. As the ice is less dense than rock, topography could “relax” or smooth, faster if ice or other low density material, such as salt, dominates the composition below the surface. Recent analysis center crater Occator Ceres suggest that the salts found there could be remnants of a frozen beneath the surface ocean, and that liquid water may have been present inside the dwarf planet .
Hydrothermal activity of the past, which could have been influenced by the surface salts Occator , also could also have something to do with erasing the craters. If Ceres cryovolcanic had activity in the past – the eruption of volatiles such as water – these cryogenic materials could have flooded the surface, possibly burying large craters. Smaller craters could have been created in the resurgent area, explains the agenica NASA .
“Somehow Ceres has healed the scars of the largest impact craters and renewed travel surfaces,” said Marchi.
NASA : overflying the dwarf panet Ceres | VIDEO
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