In March 2015, Ceres received the Dawn spacecraft without any visible signs of asteroid crashes, making the scientists wonder what happened to the missing craters.
The conclusion was that Ceres went through some kind of transformation that erased all the basins created after the impacts with asteroids.
Ceres is orbiting the asteroid belt between Jupiter and Mars, which exposes the planet to multiple crashes. His neighbor Vesta is full of craters and evidence of the impacts.
The study had been leaded by David Williams, a professor at the Arizona State University, who discovered a new model in the evolution of the small dwarf.
The team of scientists studied the data gathered by Dawn to explore the dynamic geology of the Ceres.
The first observation was that Ceres was missing craters, which was an unusual situation for an object situated in the middle of an asteroid belt. Of course, the surface has basins, but none of them was larger than 177 miles.
One of these basins was named Kerwan Basin, after the Hopi Indian spirit of young corn. Just below it, the depression called Vendimia Planitia is almost 460 miles long, more than twice the size of the basin. There might be that the depressions were unusual marks of impacts occurring before the formation of the Kerwan Basin.
As Ceres is 4.5 billion years old, it would have been impossible for no asteroid to hit the dwarf planet.
The computer simulations are calculated that there should have been at least 15 craters with sizes over 250 miles, and more than 40 holes of 60 miles across.
However, the dwarf planet has only 16 craters larger than 60 miles, and just one 177 miles long hole, the Kerwan Basin.
Thus, the scientists set out to find an explanation for the lack of marks on its surface.
The researchers looked into the planet’s composition and internal evolution. Supposing that the globe would have been rocky, the craters would have been preserved. But the observations made from Earth proved that the crust could contain ice.
When mixed with salts, ice could have done the crust become softer and to change the topography of a large crater making it smoother and even eliminate it completely.
Other elements involved in the process are believed to be the decay of radioactive elements and the icy volcanism, with molten ice instead of molten rock. As an example of cryovolcanism, the Occator Crater resembles a domed formed with materials being pushed from below.
NASA wants to keep Dawn near Ceres just until the dwarf planet gets closest to the Sun in 2018, as the scientists want to see how the heat will impact the surface.
Image Source: Flickr