At the annual American Geophysical Union meeting, NASA scientists presented the results of the latest research on bright spots on the dwarf planet Ceres. In particular, the activity detected over time, especially by NASA’s Dawn space probe with variations in their brightness confirm the possibility that on Ceres there’s still a geological activity that is modifying this dwarf planet’s surface.
The bright spots are the most visible feature of the dwarf planet Ceres. Ever since NASA’s Dawn space probe entered its orbit in March 2015, it allowed to identify over 300 of those bright spots. In an article published in the journal “Icarus” Nathan Stein of Caltech divides them into four categories:
- the bright spots made of the most reflective material, in red in the bottom image, such as the one in Occator Crater, probably composed of salts.
- those that include bright materials found in crater rims, in green in the image.
- those that include bright materials, in blue in the image, that can be found in materials ejected during crater formation.
- Mount Ahuna, in yellow in the image, where bright materials are not associated with impact craters as it’s probably a cryovolcano.
Occator crater is a special case because it contains several bright spots. The one in the central area of the crater was called Ceralia Facula, while the surrounding bright areas were called Vinalia Faculae. They seem to form distinct spots and this feature raised one of the questions that various researchers have sought an answer for, such as Lynnae Quick of the Smithsonian Institution.
The proposed explanation is that Vinalia Faculae are formed by a fluid pushed to the surface by a gas, in an event compared to the champagne that comes out of the bottle when its cork is removed. It could have been a volatile substance such as water vapor, carbon dioxide, methane or ammonia. Volatile-rich salty water could have emerged through fractures under Occator Crater and then boiled under the conditions on the surface.
Ceralia Facula is different because at a higher elevation and is brighter than Vinalia Faculae. Perhaps it was formed from a material more like icy lava that rose up through the fractures to swell in a kind of dome. There may have been several intermittent boiling phases that led to the progressive formation of the big white spot we see today.
Probably in the distant past there were many more bright spots but over the course of hundreds of millions of years many of the bright materials that formed them got mixed with other darker ones. In essence, the surface of the dwarf planet Ceres has undergone many changes over time, only partly due to impacts. Its evolution is not yet well explained but there are indications that suggest the existence of a geological activity. The mission of the Dawn space probe continues to solve these mysteries.