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Kupalo Crater on Ceres
This image of Ceres’ Kupalo Crater was captured by NASA’s Dawn spacecraft from a height of about 240 miles on Dec. 21. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)

For years, scientists puzzled over the bright spots that shine like alien headlights from the surface of Ceres, a dwarf planet in the main asteroid belt. Scientists are leaning toward identifying them as salt deposits, and now there’s a new line of evidence that could help tell the tale definitively.

The evidence takes the form of bright deposits in Kupalo Crater, one of the freshest craters spotted on Ceres. In this case, just a little bit of bright material can be seen on on the crater’s floor. But lots of the stuff is tumbling down from the crater’s rim.

The material shows up clearly in an image captured by NASA’s Dawn spacecraft. Dawn has been circling Ceres since last March, but last month it descended to a 240-mile orbit for up-close imaging. The newly released picture of Kupalo Crater was taken Dec. 21.

“This crater and its recently formed deposits will be a prime target of study for the team as Dawn continues to explore Ceres in its final mapping phase,” Paul Schenk, a Dawn science team member at the Lunar and Planetary Institute in Houston, said Tuesday in a NASA news release.

Ceres’ best-known bright spots are at the bottom of a 60-mile-wide impact basin known as Occator Crater. Last month, researchers laid out their case that the spots contain a shiny type of salt known as hexahydrite. Dawn’s readings suggest that the salts are left behind when subsurface ice on Ceres turns into water vapor.

The salts would be exposed by impacts, and if the proposed scenario holds true, that’s what the stuff on the rim of 16-mile-wide Kupalo Crater should consist of. Dawn’s science team plans to analyze the chemical signatures of the material there, as well as in the bright spots in Occator Crater and elsewhere, to clinch the case.

NASA released three other pictures on Tuesday, showing the fractured floor of 78-mile-wide Dantu Crater (plus a bright spot, by the way), parts of 25-mile-wide Messor Crater, and an unnamed 20-mile-wide crater that contains steep-sloped scarps.

Dawn was launched in 2007, and has paid visits to the asteroid Vesta as well as Ceres. The spacecraft is due to continue its mapping mission through June.

This Dec. 21 picture from NASA's Dawn spacecraft shows the fractured floor of Dantu Crater on Ceres. This cracking may have resulted from the cooling of impact melt, or when the crater floor was uplifted after formation. Similar fractures are seen in Tycho, one of the youngest large craters on Earth's moon. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)
This Dec. 21 picture from NASA’s Dawn spacecraft shows the fractured floor of Dantu Crater on Ceres. This cracking may have resulted from the cooling of impact melt, or when the crater floor was uplifted after formation. Similar fractures are seen in Tycho, one of the youngest large craters on Earth’s moon. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)
Messor Crater
This Dec. 19 image shows part of Messor Crater on Ceres. The scene shows an older crater in which a large lobe-shaped flow partly covers the northern part of the crater floor. The flow is a mass of material ejected when a younger crater formed just north of the rim. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)
Cerean crater
This 20-mile-wide crater on Ceres is covered with ridges and steep slopes, called scarps. NASA’s Dawn spacecraft captured the image from a height of 240 miles on Dec. 23. (Credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA)
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