Dwarf planet Ceres' bright spots are perhaps the strangest of all its features. Now we're finally in a low-enough altitude to get an unprecedented close-up look — and what we're seeing may only have deepened the mystery. NASA's Dawn spacecraft swung into its lowest orbit yet — a cool cruising height of 386km and started snapping pictures of a variety of features of the dwarf planet. Most of the shots are detailed images of things we'd already caught in broad-stroke versions, but there's also a clue to something perhaps bigger.
So what's the big surprise? It's that researchers are not sure that the glowing areas of the Kupalo Crater (pictured above) are caused by the same process as the ones they identified on the Occator Crater late last year.
In that case, the likely cause was salt. But in this one, researchers are not yet ready to make a final call. It could be salt, they say, but it could also be a different, as yet unknown, cause.
Here's the full slate of new snaps: