Scientists have found out there are not any big craters in dwarf planet Ceres’ surface. Instead, there are only craters of small size, which is a rare condition for the largest object in the asteroid belt between Mars and Jupiter.
Studying data from NASA’s Dawn mission, such as high-resolution images of the surface, researchers realized the biggest craters in Ceres, named Kerwan and Yalode, are about 175 miles (from 270 to 280 km) wide. Ceres is 587 miles (945 km) across, so those impact craters are not exactly big. Ceres’ surface has a wonderful composition with water ice underneath, for the lack of bigger craters.
In a study published in the journal Nature Communications, led by Simone Marchi, a senior research scientist at the Southwest Research Institute in Boulder, Colorado, scientists attributed cryovolcanoes and the dwarf planet’s surface.
Models created by researchers do not match reality
The team made a statistical modeling of collisions of large bodies with Ceres with computer simulations. Since the dwarf planet formed, it should have between 10 and 15 craters greater than 250 miles (400 km) in diameter, and at least another 40 craters larger than 60 miles (100 km) wide.
The actual surface of Ceres only show 16 craters larger than 60 miles, and there are no impact craters larger than 175 miles across.
Researchers have come with the theory that Ceres originally formed farther out in the solar system, later migrating to the asteroid belt. However, if this were the case, that would not explain the lack of massive craters, because it is believed that Ceres formed in the early days of the solar system, necessarily making it a victim of the constant collisions that identified those rough times.
According to images provided by the Dawn spacecraft, there seem to be three broad depressions across the dwarf planet’s surface. These depressions are over 500 miles wide, and they could be impact craters that have been filled in and smoothed. “Whatever the process or processes were, this obliteration of large craters must have occurred over several hundred millions of years,” Marchi said in a news release published by the NASA.
Apparently, Ceres have been smoothing over time because of the ice it is believed to be contained on its surface. As ice is less dense than stone, the smoothing process is quicker.
Salt has also been found as part of the subsurface composition of the dwarf planet. The mineral is a low-density material, that, just as ice, allows the surface to smooth and soften in a shorter period. Salt has been spotted at the center of the Occator Crater, and after some analysis scientists found that it might be left over from a frozen subsurface ocean.
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When the cryovolcanoes that are around Ceres’s surface erupt, they are releasing water from the frozen ocean. It is possible that, through the years, eruptions made materials on the surface to flow, “patching” impact craters. The smaller holes that the dwarf planets currently has would be the result of more recent impacts on the surface generated by the cryovolcanoes.
Ceres seems to be very different from Vesta, and the giant asteroid Dawn visited before Ceres. With a 300-mile-wide surface, the asteroid is covered in impact craters, including a large one that occupies most of its surface.
“The ability to compare these two very different worlds in the asteroid belt — Vesta and Ceres — is one of the great strengths of the Dawn mission,” Marchi said.
Source: NASA – Jet Propulsion Laboratory