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Based on the data obtained of Ceres from Dawn scientists have concluded that a variety of geological activities caused the bright areas on the planet, and that some of those activities could still be happening today.
Since Dawn arrived in orbit at Ceres in March 2015, scientists have located more than 300 bright areas on Ceres. A new study in the journal Icarus, led by Nathan Stein, a doctoral researcher at Caltech in Pasadena, California, divides Ceres’ features into four categories.
The first group of bright spots contains the most reflective material on Ceres, which is found on crater floors. The most iconic examples are in Occator Crater [shown in the image above, reduced and cropped to post here], which hosts two prominent bright areas. Cerealia Facula, in the center of the crater, consists of bright material covering a 6-mile-wide (10-kilometer-wide) pit, within which sits a small dome. East of the center is a collection of slightly less reflective and more diffuse features called Vinalia Faculae. All the bright material in Occator Crater is made of salt-rich material, which was likely once mixed in water. Although Cerealia Facula is the brightest area on all of Ceres, it would resemble dirty snow to the human eye.
More commonly, in the second category, bright material is found on the rims of craters, streaking down toward the floors. Impacting bodies likely exposed bright material that was already in the subsurface or had formed in a previous impact event.
Separately, in the third category, bright material can be found in the material ejected when craters were formed.
The mountain Ahuna Mons gets its own fourth category — the one instance on Ceres where bright material is unaffiliated with any impact crater. This likely cryovolcano, a volcano formed bythe gradual accumulation of thick, slowly flowing icy materials, has prominent bright streaks on its flanks.
The report is somewhat vague about why they think that there might be some geological activity even today.
The image above, released as part of this press release, gives us a simulated oblique look at Occator Crater and its bright areas. It is definitely worth it to look at the full resolution image.