Ceres’ spots suggest hydrothermal activity

Dawn data has revealed the bright spots on Ceres may have been caused by hydrothermal activity when liquid water existed below the surface of the dwarf planet.

The bright spots on Ceres’ Occator Crater. Inset shows data on the mysterious feature, with red indicating an abundance of carbonates.
Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

The bright spots on Ceres’ Occator Crater. Inset shows data on the mysterious feature, with red indicating an abundance of carbonates. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

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Studies of the bright spots on Ceres have revealed they are made predominantly of sodium carbonate, a kind of salt, and that liquid water may have existed below the surface of the dwarf planet fairly recently, in geological terms.

Ceres is the largest object in the asteroid belt in our Solar System, and has been studied by NASA’s Dawn spacecraft since it arrive there in spring 2015.

One feature that has caught astronomers’ attentions is a mysterious pattern of bright spots on its surface.

These spots are located in the Occator Crater, which is 92km wide and contains a central pit about 10km wide.

A new study using data collected by Dawn has found that the bright spots contain the highest concentration of carbonate minerals ever seen outside Earth.

It found a high percentage of sodium carbonate, which is a kind of salt found on Earth in hydrothermal environments, suggesting hydrothermal activity once occurred below the surface of Ceres.

Scientists believe this material may have come from inside the dwarf planet as it is unlikely that an impacting asteroid delivered it.

The fact that this material has reached the surface suggests temperatures inside Ceres are warmer than believed, but also that liquid water may have existed beneath the surface at one time.

These salts could be left over from a subsurface ocean or bodies of water that reached the surface and froze millions of years ago.

“The minerals we have found at the Occator central bright area require alteration by water,” says Maria Cristina De Sanctis, lead author and principal investigator of Dawn’s visible and infrared mapping spectrometer.

“Carbonates support the idea that Ceres had interior hydrothermal activity, which pushed these materials to the surface within Occator.

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We will need to research whether Ceres’ many other bright areas also contain these carbonates.”