Ceres might be the queen of the asteroid belt, but it’s a small fish compared to Jupiter and Saturn. These gas planets have been messing with the dwarf planet, changing its inclination over a short amount of time.
According to the data collected by NASA’s Dawn, over the last 3 million years, Ceres’ tilt has ranged from 2 to 20 degrees. The researchers were surprised to discover how quickly it changes. The tilt is currently at 4 degrees and was at about 19 degrees just 14,000 years ago, showing how strong of an influence the gas planets have. These results are published in Geophysical Research Letters.
This discovery was possible thanks to a careful look at the ice found on the surface of Ceres. The dwarf planet doesn’t have an atmosphere, so water ice can only survive in regions that never see the Sun, like craters.
"We found a correlation between craters that stay in shadow at maximum obliquity, and bright deposits that are likely water ice," lead author Anton Ermakov, postdoctoral researcher at NASA's Jet Propulsion Laboratory, said in a statement. "Regions that never see sunlight over millions of years are more likely to have these deposits."
The GIF shows how Ceres' northern hemisphere is illuminated by the Sun as its tilt goes from 2 to 12 to 20 degrees. NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
When the axis is close to vertical, an area of 2,000 square kilometers (800 square miles) is in perpetual darkness, but at its maximum inclination only between 1 to 10 square kilometers (0.4 to 4 square miles) remain in shadow.
Dawn showed that some of those shadowy areas both in the northern and southern hemisphere have bright deposits, and one of them has definitely got water ice.
"The idea that ice could survive on Ceres for long periods of time is important as we continue to reconstruct the dwarf planet's geological history, including whether it has been giving off water vapor," said Carol Raymond, deputy principal investigator of the Dawn mission and study co-author, based at JPL.
Understanding the geology of Ceres could help clarify the many incredible discoveries Dawn has allowed scientists to do, such us the organic molecules forming on its surface.