While studying the size and distribution of craters on the dwarf planet Ceres, scientists made a surprising discovery. The team led by Southwest Research Institute (SwRI) found that the crater distribution on the planet is fewer than expected.

Scientists expect Ceres to have at least 10 to 15 craters bigger than 400 kilometers across and 40 craters bigger than 100 kilometers wide. However, using NASA’s Dawn spacecraft,  they did not see craters bigger than 280 kilometers wide and only saw 16 crater bigger than 100 kilometers.

As stated in the study published on July 26 in the journal Nature Communications, the dwarf planet Ceres should have plenty of large craters due to collisions in the last 4.5 billion years. They only found small craters, an attribute that is unusual compared to others. By comparison, the asteroid Vesta, which is only half the size of Ceres, has large craters, even one that covers almost its side, measuring up to 500 kilometers across.

dwarf planet Ceres

Kerwan, Ceres’ largest impact crater. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

If Ceres has huge craters, the team believes that they are hidden beneath the surface. The team claims that the three circular depressions or planitiae could be impact basins caused by large collisions that occurred in the early years of the dwarf planet.

The possible explanation for the hidden huge craters could be because Ceres regenerates new surfaces repeatedly. In other words, the dwarf planet cures its own impact scars.

The ice-rich layer deep within the planet caused the craters to relax over time. It could be that the Ceres’s cryolava could have also flowed across the surface, hiding the craters over time. Admittedly, Ceres is not doing a perfect job at hiding its impact scars.

“Regardless of the specific mechanism(s) for crater removal, our result requires that large crater obliteration was active well after the late heavy bombardment era or about 4 billion year ago,” points out the study’s lead investigator, Simone Marchi, who works as a senior research scientist in SwRI’s Space Science and Engineering Division. “This conclusion reveals that Ceres’ cratering record is inextricably linked to its peculiar composition and internal evolution.”