Evidence for ice on dwarf planet Ceres
The presence of water ice in our Solar System points to potential signs of life in its early history. The latest icy candidate is dwarf planet Ceres, according to new data from NASA's Dawn spacecraft.
A graphic showing the theoretical path of a water molecule on Ceres, eventually ending up in a ‘cold trap’ crater that can store water ice for a billion years.
Evidence has been found for the presence of vast expanses of ice on dwarf planet Ceres, making it a potential candidate for having supported life in the early Solar System.
While images from NASA’s Dawn spacecraft have mostly shown Ceres as a cratered world, scientists studying Dawn data have found evidence of ice at or near its surface.
They were able to detect hydrogen in the upper surface of Ceres’ atmosphere, which is consistent with the presence of large expanses of water ice at the surface.
The water ice is likely to exist on the dwarf planet as part of a mixture of porous rocks in which the ice fills the pores. Data from Dawn's gamma ray and neutron detector (GRaND) shows that the mixture is about 10 per cent ice by weight.
"These results confirm predictions made nearly three decades ago that ice can survive for billions of years just beneath the surface of Ceres," says Thomas Prettyman, principal investigator of GRaND. "The evidence strengthens the case for the presence of near-surface water ice on other main belt asteroids."
"These studies support the idea that ice separated from rock early in Ceres' history, forming an ice-rich crustal layer, and that ice has remained near the surface over the history of the Solar System," says Carol Raymond, deputy principal investigator of the Dawn mission.
An animation of images from NASA's Dawn spacecraft showing a crater in the northern polar region of Ceres that is partly in shadow year-round.
Another study led by Thomas Platz of the Max Planck Institute for Solar System Research looked at craters on Ceres that spend most of their time in shadow in the northern hemisphere. Some of these dark craters act as ‘cold traps’ because very little of the ice within them turns into water vapour over the course of a billion years. The Dawn spacecraft was able to detect the presence of ice in one of these craters, suggesting water ice can be stored in craters on the dwarf planet.