Significant geolgocial evolution might have erased large impact craters from the surface of dwarf planet Ceres.
Ceres was thought to have many giant craters on its surface. But when NASA’s Dawn spacecraft arrived to the orbit of dwarf planet last year, scientists were surprised to find that it lacks those giant impact craters that should have been formed on its surface over its 4.5 billion-year history.
Now, scientists suggest they might have an explanation for this. Dwarf planet Ceres has experienced significant geological evolution and that persistent shifting has possibly caused to remove its biggest impact basins.
Scientists were expecting to observe more large craters on Ceres like protoplanet Vesta, which is cluttered with large craters and was the first object studied by Dawn before entering the orbit of Ceres.
Using computer simulations of collisions between Ceres and giant asteroids, researchers estimate that Ceres should have accumulated 10 to 15 giant craters stretching more than 250 miles across. But images show none of the Ceres’ crater is wider than 177 miles. Even though small craters (60 miles wide) are scattered all over the dwarf planet, they are still less than anticipated. Ceres has only 16 small craters instead of at least 40 estimated by researchers.
“When we first starting looking at Ceres image, we noticed that there weren’t any really large impact basins on the surface,” said David Williams from Arizona State University who led the team of researchers mapping the geology of Ceres.
“Even Vesta, only about half of Ceres’ size, has two big basins at its south pole. But at Ceres, all we saw was the Kerwan Basin, just 177 miles in diameter.”
So what erased Ceres’ large craters and basins?
Researchers suggest certain geological forces in and on Ceres are likely responsible for removing large basins and leaving smooth surface behind. These may include icy crust especially that of mixed with salt, internal heat generated by the decay of radioactive elements under the crust that might have brought changes in the geology of Ceres or even the cryovolcanism or icy volcanism which is evident in the bright spots scattered over Ceres, especially in crater Occator.
“It's possible that there are layers or pockets of briny water in the crust of Ceres,” said Williams. "Under the right conditions, these could migrate to the surface and be sources for the bright spots.”
But researchers are unable to reveal what exactly has smoothed the surface of Ceres.
Ceres is the largest object in the asteroid belt between Mars and Jupiter and NASA’s Dawn spacecraft has been intensively studying this dwarf planet since its arrival at Ceres in March 2015.
Dawn spacecraft is planning to continue orbiting Ceres till April 2018 when dwarf planet will make the closest approach to the Sun. It will enable researchers to see whether solar warmth triggers any changes in Ceres’ surface and it will also help test their theories.
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