Bright spots on the dwarf planet Ceres continue to confuse scientists. When a group of astronomers led by Paolo Molaro of the Astronomical Observatory of Trieste in Italy recently made observations of these features, they found something unexpected. Scientists were surprised to find that these spots become brighter during the day, and also show other changes. This variability is still a mystery.
The striking features on Ceres were discovered by NASA's Dawn spacecraft, which is orbiting a dwarf planet, constantly collecting interesting information about it. These spots reflect a lot more light than their much darker surroundings. The composition of these features is still under discussion; scientists cannot decide if they are composed of water ice, evaporated salt, or something else.
Molaro and his colleagues studied the spots on Ceres in July and August 2015 using the HARPS instrument. This instrument, mounted on a 3.6-meter telescope at the La Silla Observatory in Chile, allows radial velocity measurements with the highest accuracy available today.
Using HARPS, scientists have discovered unexpected changes in mysterious spots. However, at first they decided it was an instrumental problem. After rechecking everything, they concluded that the radial velocity anomalies were absolutely real. And then the group noticed that they correspond to the periods of time when the bright spots of the crater Occator were visible from Earth. A connection was established between them.
It's funny, but scientists still have not found a plausible explanation for the appearance of these spots.
“We don't know anything about these changes, really. This makes the stains all the stranger,”says Molaro.
One of the proposed hypotheses is that the observed changes could be caused by the presence of volatiles, which are evaporated by radiation from the sun. When the spots are on the sunlit side, they form plumes that perfectly reflect light. Scientists speculate that these plumes quickly evaporate, lose reflectivity, and produce the observed changes.
“It is already known that there is a lot of water under the surface of Ceres, so water ice or hydrate clathrates can explain everything. We will receive an exact answer from the scientists working with the Dawn probe in the coming months,”says Molaro. He also noted that the changes must be confirmed by direct shooting of Occator's bright spot at the highest resolution available.
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If the theory of the team of scientists is confirmed, Ceres is active inside. Although the dwarf planet is rich in water, it is not clear how this relates to bright spots. In addition, due to the huge reservoir of water, Ceres is being promoted as a suitable place for microbial life.
“Life as we know it on Earth needs liquid water, nutrients and a stable source of energy. Ceres is a great place in which all this is and has been for a long time, maybe billions of years. Who knows what else is there,”concluded Molaro.
ILYA KHEL