Images of Occator Crater on Ceres, which is the largest dwarf planet in the asteroid belt between Mars and Jupiter. The white areas in the crater are salt deposits. Numerous images – seen in false color – were put together here to create this animated view. Image via NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.
When the spacecraft Dawn approached Ceres in 2015, it spotted some mysterious bright spots on the surface of this dwarf planet. Eat on Ceres was so highly reflective that viewers joked for a while about strange lights. Scientists were at first surprised, and wondered what caused the reflectivity. It turned out that there are several bright spots on Ceres, and they are now known to be salt deposits on this surface of this small world, mostly composed of sodium carbonate. Scientists said the stains probably came from liquid that percolated and evaporated to the surface of Ceres, leaving a salt churn. But percolated up where? In October 2018, when Dawn’s mission ended, the spaceship dived to 35 km above the surface of Ceres. The craft saw new details in the bright areas that scientists have now turned to to explain the origin of the bright spots.
Dawn scientists now say that the salty liquid on Ceres ‘surface came from a reservoir of brine, like salt-rich water, deep inside Ceres’ interior. Scientists say this salt reservoir is about 25 miles (40 km) deep and hundreds of miles wide. Ceres itself is less than 600 miles (1,000 km) away. That, in other words, Ceres is now understood to have a relatively large interior reservoir of brilliant water.
The findings, which also reveal the extent of geological activity in the Occator Crater – the home of Ceres’ most famous bright spots – appear in a special collection of papers published by Natural Astronomy, Nature Geoscience, en Nature communication on August 10, 2020.
In 2015, when NASA’s Dawn spacecraft approached the dwarf planet Ceres, it saw 2 strange bright spots on the surface of Ceres. Viewers joked about ‘strange headlights’, but could not yet explain the spots. Now they are known to be relatively recent salt deposits. This image is from 19 February 2015, purchased at a distance of almost 29,000 miles (46,000 km). It turns out that the brightest spot on Ceres has a dimmer companion, located in the same crater, now called Occator Crater. Image via NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.
Ceres’ bright spots are only 240 kilometers above its surface (lower than the International Space Station is above the Earth). Image via NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.
An image of Occator Crater – and the bright spots – draped over a digital terrain model, providing a 3-D-like perspective image. Image via NASA / JPL.
Ceres – classified in 2006 as a dwarf planet by the International Astronomical Union (IAU), at the same time Pluto was derived from full planetary status – was once called the asteroid Ceres and was the first asteroid discovered in 1801.
There were hints of bright regions on Ceres long before Dawn’s arrival in 2015. Scientists looked through diffuse bright areas of an unknown nature on the dwarf planets. The scientists’ statement said they:
… knew that micrometeorites often placed the surface of Ceres, making it rough and leaving debris. Over time, such action would have to darken these bright areas. That their brightness indicates that they are probably young. Trying to understand the source of the areas, and how the material could be so new, was a major focus of Dawn’s definitively expanded mission, from 2017 to 2018.
From its narrow orbit, Dawn retrieved detailed images of two distinct, highly reflective areas within the Occator Crater, which later became Cerealia Facula and Vinalia Faculae (“faculae” means bright areas).
The study not only confirmed that the bright regions are young, some less than 2 million years old. It also found that the geological activity driving these deposits could continue. This conclusion was dependent on scientists who made an important discovery: salt compounds (sodium chloride chemically associated with water and ammonium chloride) concentrated in Cerealia Facula. The scientists explained:
On the surface of Ceres dehydrate salt with water rapidly, within hundreds of years. But Dawn’s measurements show they still have water, so the fluids must have reached the surface recently. This is evidence of both the presence of fluid beneath the Occator Crater region and continuous transfer of material from the deep interior to the surface.
In our solar system, icy geological activity occurs mainly on icy moons, where it is driven by its gravitational interactions with its larger planets. But that is not the case with the movement of bricks to the surface of Ceres, because this small world is not particularly close to large bodies in space that might attract it. Instead, scientists found two main paths that allow liquids from the interior of Ceres to reach the surface. Dawn lead researcher Carol Raymond said:
For the large castle at Cerealia Facula, most of the salt was supplied from a slushy area just below the surface that was melted by the heat of the impact that formed the crater about 20 million years ago. The impulse heat dropped after a few million years; However, the impact also created large fractures that could reach the deep, long-lived reservoir, allowing brine to continue to percolate to the surface.
The discovery of this pleasurable continuous activity on Ceres – this movement of briny water from the interior to the surface – suggests that there are other large, icy bodies in our solar system. net moons can also be active.
This mosaic image uses false color to mark the recently exposed brine, as salty liquids that were pushed up from a deep reservoir under Ceres’ crust. In this view of an area of Occator Crater they appear red. Image via NASA / JPL-Caltech / UCLA / MPS / DLR / IDA
Dawn is the only spaceship that ever orbited two alien destinations: Ceres and the giant asteroid Vesta. This dual mission was made possible by Dawn’s ion propulsion system. The scientists’ statement stated:
When Dawn used the last of an important fuel, hydrazine, for a system that controls its orientation, it could not yet use Earth’s means of communication, nor to point its solar rays at the sun to produce electrical power. Because Ceres had organic matter on its surface and liquid beneath the surface, planetary protection rules required that Dawn be placed in a long-term environment, which would prevent the planet from affecting the dwarf planet for decades.
NASA Dawn Mission Director Marc Rayman said in a statement:
Dawn succeeded much more than we hoped when it began with its extraordinary foreign expedition. These exciting new discoveries at the end of its long and productive mission are a wonderful tribute to this remarkable interplanetary explorer.
This mosaic of Ceres’ Occator Crater is composed of images from NASA’s Dawn mission, captured on its second extended mission, in 2018. Bright pits and mounds (foreground) were formed by saline fluid released as the water-rich floor of Occator frozen after the crater-forming impact about 20 million years ago. Image via NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / USRA / LPI.
Bottom line: Scientists studying space data Dawn now say that the salt deposits on the surface of Ceres came from a reservoir of brine, or salt-rich water, deep in the interior of the dwarf planet. This brine reservoir is estimated to be about 25 miles (40 km) deep and hundreds of miles wide … remarkable on a small world less than 600 miles (1000 km) across.
Sources (Collection): Dawn XM2 at Occator Crater
Via NASA
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