Is there water on asteroids?
The answer is yes. The biggest asteroid in the asteroid belt is called Ceres. In fact, it is also considered as a dwarf planet. NASA’s Dawn spacecraft, currently orbiting Ceres since 2015, sent convincing results concerning the presence of water on this dwarf planet.
Two different teams of researchers came up with the same conclusion: water has an important role in the evolution of Ceres.
The first team, led by Andrea Raponi from the Italian National Institute of Astrophysics, focused their research on the Juling Crater located in the asteroid’s midlatitudes. Thanks to the Dawn spacecraft, a patch of ice was seen growing from 3.6 km2 to 5.5 km2 over six months. This event was not expected considering that the crater is located where the sun is higher overhead and the shadows are harder to maintain. Raponi’s team suggested two explanations for this phenomenon. The first possibility is that, as the subsurface of Ceres is made of water ice, a landslide along the crater’s wall would uncover the sub-layer and thus make the ice patch appear to grow. The second possibility, prefered by the team, involves water vapor. In this instance, a source of heat would make the water ice from the subsurface evaporate. The water molecules would get trapped by the crater wall forming a thin layer of liquid water, which would rapidly freeze at the surface of the cold wall.
A second team from the same institute, led by Filippo Carrozzo, mapped several regions of the asteroid in detail, focusing their survey on carbon-rich minerals. It is important to understand that Ceres has no atmosphere, which means that the temperature on the surface of the planet causes any liquid to boil away immediately. Therefore, finding water in its liquid form is highly unlikely. However, as water evaporates, traces of minerals, such as carbonates, can be found on the surface, which is how scientists can claim the presence of water. The Dawn spacecraft revealed over a hundred bright patches on the surface of the asteroid which contained sodium carbonates. The team found that the most recent traces of sodium carbonates were more likely to carry water molecules inside their structures.
These two findings hence reinforce evidences that Ceres’ surface is continuously changing and that water is of great significance to its evolution.
Stay tuned for more scientific insights on the asteroid Ceres from NASA’s Dawn spacecraft.
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Picture from: https://www.nasa.gov/subject/6883/ceres/