One of the weirdest features of the asteroid belt's biggest dwarf planet Ceres is a series of bright spots in the center of the large Occator crater. NASA's Dawn spacecraft has revealed that the bright center of the crater is actually home to a dome shape highlighted by reflective salts. New research suggests the bright material, dubbed Cerealia Facula, is actually much younger than the rest of the crater and that the central dome could be the result of cryovolcanic activity.

"The age and appearance of the material surrounding the bright dome indicate that Cerealia Facula was formed by a recurring, eruptive process, which also hurled material into more outward regions of the central pit", says Andreas Nathues, who works on the Dawn mission from the Max Planck Institute for Solar System Research in Germany.

The bright, salty deposits are estimated to be 30 million years younger than the rest of the crater, leading Nathues and his team to theorize that Occator Crater was created by a large impact some 34 million years ago and that the dome, aged only four million years, rose up much later and started tossing shiny sub-surface brine all over the place.

"The large impact that tore the giant Occator Crater into the surface of the dwarf planet must have originally started everything and triggered the later cryovolcanic activity," says Nathues.

The researchers think the ancient impact disrupted things enough that the brine was able to move closer to the surface and that escaping gases could have formed a system of vents that led to eruptions and deposited salts to form the central dome and other bright spots.

In other words, there's reason to believe that Ceres' bright spots were put there by salty, icy volcanoes over time, ending with the final layer of the dome being laid down four million years ago. Nathues says similar domes have been observed on Jupiter's moons Callisto and Ganymede.

The scientists aren't sure if all cryovolcanism in Occator has gone totally dormant or ceased. It could be ongoing at a lower level, they say, as supported by images that show haze in the crater from certain angles.

The research was published in The Astronomical Journal.

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