The Mystery of Ceres: the reason for the formation of bright regions on the surface of a dwarf planet

(ORDO NEWS) — Analysis of data from NASA’s Dawn spacecraft has allowed scientists to study close-ups of the surface of the dwarf planet Ceres, which lies in the main asteroid belt between Mars and Jupiter. By the time the mission was completed in October 2018, the orbiter had descended less than 35 kilometers above the surface, making it possible to see mysterious objects on the surface in incredible detail.

Scientists have found that the bright areas are sediments composed mainly of sodium carbonate – a compound of sodium, carbon and oxygen. Most likely, they arose from a liquid that seeped to the surface and evaporated, leaving behind a highly reflective salt crust. However, the nature of the origin of this liquid has not yet been determined.

After analyzing the data collected near the end of the mission, the scientists concluded that the liquid came from a deep reservoir of salt-enriched water. By studying Ceres’ gravity, scientists have learned more about the inner structure of the dwarf planet and were able to determine that the reservoir is about 40 kilometers deep and hundreds of kilometers wide.

Ceres does not benefit from the internal heating caused by gravitational interaction with the large planet, as is the case with some icy moons in the outer solar system. But new research, which focuses on the 92-kilometer-wide crater of Ceres called Occator, home to the most expansive bright regions, confirms that Ceres is a rich watery world.

The results of the new study, which was published Aug.10 in the journals Nature Astronomy, Nature Geoscience and Nature Communications, also show the extent of geological activity in Occator Crater.

Long before the spacecraft arrived at Ceres in 2015, scientists spotted diffuse bright regions through telescopes, but their nature was unknown. As it approached, the spacecraft captured images of two separate, highly reflective areas in Occator Crater, which were later named Cerealia Facula and Vinalia Faculae. (“Faculae” means light areas).

Scientists knew that micrometeorites often coat the surface of Ceres, causing bumps and debris. Over time, doing this should darken these bright areas. Thus, their brightness indicates that they are probably relatively “young”.

The study not only confirmed that the bright regions are young – some less than 2 million years old; it also found that geological activity leading to such deposits could continue. This conclusion arose after scientists made a key discovery: they identified salt compounds (sodium chloride chemically bound to water and ammonium chloride) concentrated in Cerealia Facula.

On the surface of Ceres, salts that carry water quickly dehydrate over hundreds of years. But Dawn’s measurements show they still have water in them, so the fluids must have reached the surface quite recently. This indicates both the presence of liquid below the Occator crater region and the ongoing transfer of material from deep bowels to the surface.

 

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