Pluto may be the star of the dwarf planet scene for the next few days, but let's not forget about Ceres: We've been salivating over the mysterious white spots on its surface since NASA's Dawn orbiter sent its first photos home. But according to the mission's principal investigator, the crowd favorite theory -- that the spots are made of some kind of water or ice -- is probably about to be debunked.
— NASA's Dawn Mission (@NASA_Dawn) July 6, 2015
According to Christopher Russell of the University of California at Los Angeles, the Dawn mission's principal investigator, the team is "shying away from there being ice on the surface."
"The general consensus on the team right now is that water is definitely a factor on Ceres, but that the spots themselves are more likely to be just highly reflective salt, rather than water," Russell told The Post.
The mystery is far from completely solved, Russell cautioned. The team failed to get the quality of measurements they wanted in examining the spots, and they'll have to try again at a closer orbit -- like the next planned mapping orbit, which will take them from 2,700 miles over the surface to just 900. The photos taken at that height will also have significantly better resolution, which should further help the team determine what the spots are made of.
But based on the spectral data the team did get, Russell said, the spots "really don't look like mounds of ice."
That doesn't mean water isn't important on Ceres. We already know that there's water vapor in the planet's atmosphere. But while it was reasonable to think that the water-vapor find and the bright spots might be linked, Russell said — with the dots representing geysers, fountains, or places where water seeped out of the ground — salt is now the most likely culprit.
"The bright spots are probably — like you might find in the desert on Earth — a salt plain where maybe water came out at one time and evaporated," Russell said.
The spacecraft's current mapping orbit is going to be extended while mission scientists investigate an anomaly Dawn recently experienced, but they report that the closer orbit will still occur — whenever they decide to move forward. Until then, the resolution of the spot mystery will remain unconfirmed.