Bright spots on Ceres’ surface are large salt reservoirs

Hyperaxion Aug 13, 2020

Thanks to the Dawn spacecraft, scientists have solved the mystery about bright spots on the dwarf planet, something that has puzzled scientists for years.

NASA astronomers have discovered that the bright areas on the dwarf planet Ceres, located in the asteroid belt between Mars and Jupiter, are deposits composed mainly of sodium carbonate – a compound of sodium, carbon, and oxygen. The results of this and other analyzes were published this week in seven articles in the journal Nature.

Bright spots on Ceres’ surface are large salt reservoirs
(Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA).

The mysterious bright spots have puzzled scientists for years. So, when NASA’s Dawn spacecraft approached Ceres in 2015, the researchers took the opportunity to investigate those regions thoroughly. The data reveal that the reservoir is approximately 40 kilometers (25 miles) deep and hundreds of kilometers wide.

“Dawn accomplished far more than we hoped when it embarked on its extraordinary extraterrestrial expedition,” said mission director Marc Rayman. “These exciting new discoveries from the end of its long and productive mission are a wonderful tribute to this remarkable interplanetary explorer.”

The focus of the observations on the dwarf planet was the Occator Crater, more specifically the regions named Cerealia Facula and Vinalia Faculae, where there is a high concentration of bright spots.

(Credit: NASA / JPL-Caltech / UCLA / Max Planck Institute for Solar System Studies / German Aerospace Center / IDA / PSI).

The research not only confirmed that the bright regions are young (some less than 2 million years old), but also found that the geologic activity that creates the reservoirs may be in progress.

According to the researchers, on the surface of Ceres, salts containing water dehydrate quickly, in a matter of hundreds of years. However, measurements made by the Dawn mission showed that salts in the crater still have water, suggesting that somehow fluids reached the surface of the dwarf planet not long ago.

“For the large deposit at Cerealia Facula, the bulk of the salts were supplied from a slushy area just beneath the surface that was melted by the heat of the impact that formed the crater about 20 million years ago,” said Carol Raymond, one of the leaders of the study. “The impact heat subsided after a few million years; however, the impact also created large fractures that could reach the deep, long-lived reservoir, allowing brine to continue percolating to the surface.”

Part of the Occator Crater in Ceres.
Part of the Occator Crater in Ceres. (Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/USRA/LPI).

Scientists were also able to map the density of Ceres’ crust structure. Using gravity measurement data of the dwarf planet, they found that the density of the crust increases significantly with depth.

This indicates that the cause of the phenomenon goes beyond pressure. For the astronomers, while Ceres’ reservoir is freezing, salt and mud are being incorporated into the lower part of the crust, increasing its density.

(Credit: / animations credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA / produced & edited by Steve Spaleta).


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