An international team of scientists has used data from NASA’s Dawn spacecraft to gain a crucial insight into what lies beneath the surface of the dwarf planet Ceres.
The research, published in Science, looked at the water ice and metal distribution throughout the dwarf planet’s exterior. Ceres seems to have extensive ice deposits in mid-to-high latitude (about 40°), just a meter from the surface, though has a curious lack of iron.
According to the researchers, the material that makes up the dwarf planet organized itself into layers due to internal processes, making the surface rich in water and metal-poor.
“The interior of Ceres was warmed by short-lived radioisotopes, injected into the solar nebula by nearby supernovae. This warming produced liquid water that altered the silicates within Ceres' interior producing hydrated minerals,” lead author Dr Tom Prettyman from the Planetary Science Institute in Tucson, Arizona told IFLScience.
The bulk composition of the dwarf planet and its surface is very different, and this is due to the past presence of liquid water, which lead to the formation of different chemical compounds and ice layers.
“During Ceres' early history liquid water was present in Ceres' interior. Some of the water was consumed by serpentinization, wherein the water was incorporated as OH in the crystal lattice of serpentine group minerals and other hydrated species,” continued Prettyman. “Some of the residual water not spent by this process exists today in Ceres' regolith as ice. The amount of ice is yet another constraint on the present state and evolution of Ceres.”
This serpentinization process trapped a significant fraction of the original water and it is one of the many processes that has kept Ceres’ ice content for billion of years. The top layer of soil also protects the ice deposits, reducing the dwarf planet’s water loss.
“The deeper the ice, the harder it is for the water molecules to escape. Some molecules do find their way, but the loss rate is very low. The temperatures on Ceres are low enough that production of water vapor at the interface between the ice table and soil is very low,” said Prettyman.
This study has confirmed previous estimations of the ice content on Ceres, based on its density, and it proves that ice can survive even in the top layers of an atmosphereless world for billions of years.