The mysterious bright spots of Ceres have been puzzling scientists since they have been discovered last year, as latest observations by NASA's Dawn probe suggest that these are highly reflective material on the surface of the dwarf planet. 

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Now, the latest observations reveal that these spots are made from volatile material that evaporates in sunlight. Scientists also report that they observed how these spots are changing, that brighten then fade during the course of the day. 

To date, there are 130 bright spots on the surface of Ceres that have been identified, where these regions apparently reflect more light than their surroundings but scientists still do not know what causes these spots and what they are made of. When NASA released photos of the bright spots located inside the craters, many scientists speculate that these are made from hydrated magnesium sulfates or simply put, salt.

Now, in this new study, scientists from the INAF-Trieste Astronomical Observatory in Italy suggest that there is more than just salt in these bright spots than first thought. The team led by Paolo Molaro utilized the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph in the European Southern Observatory in Chile where they targeted the brightest spot of Ceres, which is located inside the Occator crater.

The team observed this particular spot for two nights in last July and August where they noticed that the cluster of spots becoming brighter and dimmer over the course of the day, which is not related to the dwarf planet's rotations. 

Molaro says that these brights spots were truly surprising as anyone would have expected the dwarf planet to be completely dark, pockmarked with impact craters from asteroids. As scientists discover more and more about these spots, these indicate that the planet could be hiding some sort of activity even on a short, temporal scale, which is truly unexpected from an isolated body that is very distant from any gravitational forces of other planets.

Researchers say that these changes in the spots are caused by the presence of volatile substances that disappear or evaporate in sunlight. As the crater faces the sun, the spots apparently form plumes that can reflect sunlight effectively however, they evaporate quickly where they lose all reflectivity. 

Molaro reveals that they still do not know what kind of material this is but he suggests that if this was simple material, then it could water vapor or ice however, more complicated material are not to be dismissed. In order to determine for sure the composition of these spots, data and images from NASA's Dawn probe are crucial. To date, scientists confirm that there is a lot of water found in Ceres' interior but in this new study, this study is only limited to the changes of reflectivity of the spots that are measured.

He concludes that the real nature of these bright spots can only be determined ultimately by the Dawn mission where they can hopefully learn and repeat their measurements with a new technique.

This new study is published in the Monthly Notices of the Royal Astronomical Society.