The dwarf planet Ceres, at 587 miles wide the largest object in the main asteroid belt between Mars and Jupiter, has a different surface composition than previously thought—and it took NASA and DLR’s Boeing 747-based SOFIA observatory to make the distinction. By observing Ceres in mid-infrared, only possible from high altitudes above infrared-absorbing water vapor, SOFIA found that Ceres is covered in silicates—pyroxenes—that likely came from impacts, the result of infalling material from elsewhere in the asteroid belt…the “dust” of asteroid collisions.
Ceres’ Haulani Crater, with a diameter of 21 miles (34 km), shows evidence of landslides from its crater rim. Smooth material and a central ridge stand out on its floor. This image was made using data from NASA’s Dawn spacecraft when it was in its high-altitude mapping orbit, at a distance of 915 miles (1,470 km) from Ceres.
This enhanced color view allows scientists to gain insight into materials and how they relate to surface morphology. Rays of bluish ejected material are prominent in this image, the color having been associated with young features.
After more than a dozen years of head-scratching we finally have our first really good look at the weird bright spot on Ceres, thanks to NASA’s Dawn spacecraft and its low-altitude mapping orbit (aka LAMO) around the dwarf planet. Appearing from 240 miles up as a dome covered in cracks and rising from the surrounding darker terrain, the largest of Ceres’ bright spots looks not unlike… a giant pimple.
Researchers using the High Accuracy Radial velocity Planet Searcher (HARPS) instrument on ESO’s 3.6-meter telescope at La Silla have detected “unexpected” changes in the brightness of Ceres during observations made in July and August of 2015. Variations in line with Ceres’ 9-hour rotational period were expected, but other fluctuations in brightness were also found that indicate albedo changes on a daily, diurnal basis.
Long story short: Ceres is slowly “blinking.”
So now that NASA’s Dawn spacecraft has been in orbit around Ceres for seven months, has the nature of its strange bright spots finally been determined? Are they brilliantly reflective deposits of water ice, as many initially suspected? Or just some curiously-bright rock faces? (Or the metallic remains of an ancient alien space base, like more than a few folks have imagined?) As it turns out, Ceres’ bright spots may be none of these (and especially not that last one… puh-leeze) — they may be enormous deposits of salt.