[LINK] "Two mysterious bright spots on dwarf planet Ceres are not alike"

[rfmcdonald]

New Scientist's Jacob Aron reports on the latest mystery to emerge from Ceres.

The unidentified bright spots on dwarf planet Ceres have become more mysterious. The spots on the surface were first glimpsed close-up just a month ago, and now infrared images reveal that they have different thermal properties.

NASA's Dawn spacecraft is currently in orbit around the dwarf planet, which sits in the asteroid belt between Mars and Jupiter. Mission scientists presented the latest results from the spacecraft at the European Geosciences Union General Assembly in Vienna, Austria, today.

Two spots on the surface, labelled feature one and feature five, show up in visible light images as very bright in comparison to the rest of Ceres's dull grey, leading to speculation that they could be the sites of watery volcanoes on the dwarf planet, also known as cryovolcanoes.

Now Federico Tosi, who works on Dawn's Visible and Infrared Spectrometer, has presented infrared images of the two spots, measuring their thermal properties. "What we have found is that bright spot number one corresponds to a dark spot in the thermal image," he said at a press conference today. In other words, the bright spot is much cooler than its surroundings.

In comparison, feature five, which appears as two separate bright spots next to each other in visible images, didn't show up in the infrared images. "Spot number five shows no distinct thermal behaviour," he said, meaning it is the same temperature as its surroundings. At the moment Dawn is too far away from Ceres to determine whether this is due to the bright spots being made from different stuff, or due to a different structure on the ground.