Two new studies have provided evidence that the dwarf planet Ceres might have had a global liquid ocean on its surface in the past, and that maybe some of this water is still present underneath its crust.
Researchers have looked at the composition of Ceres' crust and discovered that it’s a mixture of ice, salts, and hydrated material. Planetary scientists consider a lost water ocean the most likely scenario to explain this.
"More and more, we are learning that Ceres is a complex, dynamic world that may have hosted a lot of liquid water in the past, and may still have some underground," Julie Castillo-Rogez, Dawn project scientist and co-author of the studies, based at NASA's Jet Propulsion Laboratory (JPL), said in a statement.
The first study, published in the Journal of Geophysical Research: Planets, used the gravitational anomalies of the dwarf planet to establish its composition and interior structure. Scientists had a general idea of what Ceres should be like but there are some discrepancies. "Ceres has an abundance of gravity anomalies associated with outstanding geologic features," added the lead author of this study, Anton Ermakov, also at JPL.
Occator crater, the location of Ceres’ bright spots, or the lonely tall mountain Ahuna Mons are good examples. These and many others seem to be associated with cryovolcanism phenomena, hinting at a world that is geologically active.
This approach also discovered that the crust has a density closer to ice than rock. This was a bit of an issue since previous studies suggest that the crust is much stronger than regular ice. That’s where the second study, published in Earth and Planetary Science Letters, comes in.
The analysis suggests that Ceres' crust is a mixture of ice, salts, rock, and clathrate hydrate, a crystalline solid with very interesting properties, which is made from water and small gaseous molecules. Clathrate hydrates have the same density as water ice but can be between 100 and 1,000 times stronger than regular ice.
This composition fits well with the scenario of a slowly changing Ceres. The dwarf planet had more pronounced features which have disappeared over time. The crust likely rests on a more deformable layer, which might still contain a liquid component. This might be the remains of an ocean that could have covered the dwarf planet 4 billion years ago.
Ceres is the largest object in the asteroid belt and the only dwarf planet in the inner solar system. The Dawn mission has just been extended to continue studying the planet for another year.