Ceres' mysterious bright spots are clearer and sharper than ever, thanks to NASA's Dawn mission. The mission will need to get much closer to answer all of our questions and provide all of the details, but these recent views provide some interesting insights.
On May 16th the spacecraft shot the latest sequence of images to enable its navigation over the dwarf planet. The 4,500 mile orbit revealed that the crater which contains the bright spots is framed by a series of cracks or furrows in the crust of Ceres.
Christopher Russell, principal investigator for the Dawn mission, believes that although the precise nature of the spots remains unsure, this latest information reduces the number of possibilities: "Dawn scientists can now conclude that the intense brightness of these spots is due to the reflection of sunlight by highly reflective material on the surface, possibly ice."
On a surface like that of Ceres ice cannot remain for too long; eventually it will sublimate unless covered by dust or other debris, much like ice exposed on Mars in the past. This lets us know that if the bright spots are ice, they are fairly new features.
Although many have posited that these bright spots are the same captured by the Hubble Telescope a significantly lower resolution in 2004, this is apparently not the case. The Bad Astronomy blog reports that Joe Parker, part of the 2004 Hubble team, confirms that these are not the same spots. It is unlikely that they formed after 2004, and more likely that compared to Hubble's resolution they aren't bright enough to be visible distinct from the rest of Ceres, which is dark. What happened to the spot Hubble found is unclear.
As Ceres rotates, sunlight bounces off the spots, especially at sunrise and sunset. Phys.org and Bob King of Universe Today speculate that the spots may be elevated, located near the side of a hill or mountain. This leads King to ask the question: "Could we be seeing relatively fresh ice or salts after recent landslides related to impact or tectonic forces exposed them to view?"
Whatever the ultimate answer, more exploration will have to take place before we can understand it.
