NASA̵7;s Dawn spacecraft gave scientists special close-ups of the dwarf planet Ceres, located in the main asteroid belt between Mars and Jupiter. By the time the mission ended in May 2018, the spacecraft had dropped below 22 miles (35 km) above the surface, revealing sharp detail in the mysterious bright areas Ceres has become famous for.
Scientists have found that bright areas are sediments made up mainly of sodium carbonate – a compound of sodium, carbon and oxygen. They can come from a liquid that seeps to the surface and evaporates, leaving behind a highly reflective salt crust. But what they have yet to determine is where the liquid came from.
By analyzing the data gathered near the end of the mission, the Dawn scientists concluded that the liquid came from a deep saltwater reservoir, or water enriched with salt. By studying Ceres’ gravity, scientists learned more about the inner structure of the dwarf planets and were able to determine that the saltwater reservoir was about 25 miles (40 km) deep and hundreds of miles wide.
Ceres do not benefit from the internal heating produced by gravitational interactions with a large planet, as is the case with some of the icy moons of the outer solar system. But new research, focusing on Ceres’ 57-mile (92-kilometer) Occator crater – home to the widest of bright areas – confirms that Ceres is a water-rich world like other icy objects.
The findings, which also reveal the extent of geological activity in Occator crater, appear in a special collection of articles published by Natural Astronomy, Natural geoscienceand Natural media on August 10.
“Dawn has achieved more than we could have hoped for by embarking on her extraordinary extraterrestrial expedition,” said Marc Rayman, Mission Director of NASA’s Jet Propulsion Laboratory in Southern California. . “These exciting new discoveries after the end of its long and efficient mission are a great tribute to this remarkable interplanetary explorer.”
Bright mystery solving
Long before Dawn arrived at Ceres in 2015, scientists noticed areas of light diffusing with a telescope, but their nature is still unknown. From its close orbit, Dawn captured two distinct, highly reflective areas inside the Occator crater, later named Cerealia Facula and Vinalia Faculae. (“Faculae” means bright areas.)
Scientists know that microscopic particles frequently peel the surface of Ceres, making it rough and leaving debris behind. Over time, that kind of action will darken these bright areas. So their luminosity suggests they may be young. Trying to understand the origins of the regions and how the document could have become so fresh, was the main focus of Dawn’s last expansion mission, from 2017 to 2018.
The study doesn’t just confirm that the bright areas are young – about less than 2 million years old; it also found that the geological activity driving these mines may be in progress. This conclusion depends on the scientists making an important discovery: salt compounds (sodium chloride chemically bound to water and ammonium chloride) are concentrated in Cerealia Facula.
On the surface of the Ceres, the aqueous salts rapidly dehydrate within hundreds of years. But Dawn’s measurements showed they were still water, so the liquid must have surfaced recently. This is evidence of the presence of liquid underneath the Occator crater region and the transition of matter from deep within to the surface.
Scientists have found two main routes that allow liquids to reach the surface. “For the large mine in Cerealia Facula, most of the salt is provided from a bubbling area just below the surface that was melted by the crater formation impact about 20 million years ago,” said Carol Raymond, Investigator Dawn’s main said. “The impact heat decreases after a few million years; however, the impact also creates large cracks that can reach deep, long-lasting aquifers, allowing salt water to continue seeping into the surface.”
Active Geology: Recent and Abnormal
In our solar system, icy geological activity mainly occurs on icy moons, where it is driven by gravitational interactions with their planets. But that was not the case with the movement of salt water onto the surface of the Ceres, suggesting that other large ice-rich celestial bodies other than the moon could also be active.
Some evidence of recent Crater fluids occurs from bright sediments, but other clues come from a series of interesting conical hills reminiscent of Earth’s pingos – glacial mountains small in the polar regions are formed by groundwater with freezing pressure. Such features have been discovered on Mars, but their discovery on Ceres marks the first time they have been observed on a dwarf planet.
On a larger scale, scientists could map the density of the Ceres crust’s structure as a function of depth – a first for an ice-rich planet. Using gravity measurements, they found that the Ceres’ coating density increased significantly with depth, far beyond the simple effect of pressure. The researchers deduced that at the same time the reservoir of Ceres froze, the salt and the mud combined into the lower part of the crust.
Dawn is the only spacecraft to ever orbit two extraterrestrial destinations – Ceres and the giant asteroid Vesta – thanks to its efficient ion propulsion system. When Dawn uses the last critical fuel, hydrazine, for a system that controls its direction, it cannot point at Earth to communicate nor direct its energy arrays at the Sun to generate energy. electricity. Since Ceres is found to have organic material on the surface and liquid below the surface, planetary protection rules require Dawn to be placed in a long-term orbit to prevent it from impacting the dwarf planet in many decade.
Ceres dwarf planet is an oceanic world: research
“Recent Cryovolcanic activity at the crater occurred on Ceres”, A. Nathues et al. 2020 August 10 year Natural Astronomy www.nature.com/articles/s41550-020-1146-8
“Mobilization is based on the impact of deep crust Brines on Dwarf Planet Ceres”, CA Raymond et al. 2020 August 10 year Natural Astronomy www.nature.com/articles/s41550-020-1168-2
“Proof of Ceres Heterogeneous Crust from Dawn’s High Resolution Gravity Data”, RS Park et al., 2020 August 10, Natural Astronomy www.nature.com/articles/s41550-020-1019-1
“New replacement of hydrated sodium chloride on cereals from rising salty liquids”, MC De Sanctis et al., 2020 August 10, Natural Astronomy www.nature.com/articles/s41550-020-1138-8
“The heat-induced volatile redistribution at the crater occurred on Ceres as a planetary comparison process,” P. Schenk et al., 2020 August 10, Natural media www.nature.com/articles/s41467-020-17184-7
“Various Sources of Brines Forming Faculae in the Ceres’ Emplaced Crater through Hydrothermal Brine Spray,” JEC Scully et al., 2020 August 10, Natural media www.nature.com/articles/s41467-020-15973-8
“Cold glass formation following the impact of mounds and hills in Ceres’s crater,” BE Schmidt et al., 2020 August 10, Natural geoscience www.nature.com/articles/s41561-020-0581-6
Provided by Jet Propulsion Laboratory
Quote: Mystery solved: The bright areas on the Ceres come from the saltwater below (2020, August 11) accessed August 11, 2020 from https://phys.org/news/2020-08 -mystery-bright-areas-ceres-salty.html
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