Thanks to NASA’s Dawn spacecraft, we’re finally seeing more of the asteroid Ceres than a fuzzy ball. This mosaic, assembled from images taken in blue, green, and infrared spectral filters, shows the dwarf planet’s surface in false color:
The color scheme in this map is inverted from reality: the version JPL released assigns the short, bluer wavelengths to be red, and the long, infrared wavelengths (which the human eye can't see) to be blue. That seemed a wee daffy to me, so I asked what was up. Turns out the camera team wanted the map to look unreal: it's too early in the mission to unambiguously separate all the things that influence the surface's apparent color, and when the team made a map with a different color scheme, it led to misleading interpretations even among the team's own members. So instead they decided to emphasize the "false" in false-color and forestall confusion.
But the colors do help us pick out surface differences. The asteroid’s surface definitely has variety; as the press release from JPL explains, the images suggest that Ceres was once more active geologically. That’s not surprising: between 17% and 27% of Ceres’ mass is water, and planetary scientists have speculated whether it might have had (or even still have?) a subsurface water ocean driving geology up top. There are also fewer large craters than expected.
Dawn has only just begun its investigation, so we’ll have to wait until it spirals closer to the asteroid’s surface to better understand Ceres.
You can read more about the Dawn mission in our April 2015 issue. You can also explore Ceres as a globe in this web tool adapted by astronomy enthusiast Grzegorz Czepiczek. And don't forget about the mission director's Dawn Blog, either.