You never know what might be hiding in the shadows. There’s a vast empty space between Mars and Jupiter that’s peppered with rocky, icy remnants of the early solar system. This is the asteroid belt, and the largest object here is Ceres, a dwarf planet about the size of Texas.
Ceres Carters: An animation of Ceres’ northern craters where the sun really doesn’t shine. Credit: Thomas Platz, et. al.
Though Ceres was discovered in 1801, we hadn’t gotten a lot of new information about the mysterious dwarf planet before 2015, when the Dawn mission started making observations.
As described in a newly published paper in Nature Astronomy, researchers looking at photos sent back by Dawn noticed that about 600 of Ceres’ many craters were shrouded in constant shadow–so deeply so that their bases were never lit by the sun. Ten of these craters had curious bright spots located in their depths. The scientists took a closer look to see what was going on in there.
Turns out that those bright spots in the dark may contain water ice. The researchers think the water ice could have entered the craters in one of two ways.
One possibility is that the ice formed when the icy interior of Ceres erupted in a cryovolcano–a volcano spewing ice (instead of lava) over a large enough area that some of it got into the craters. That’s a real possibility since a cryovolcano half the size of Mount Everest has been identified on Ceres’ surface. But the ice could also have gotten there in the same way the craters themselves were created–when an asteroid slammed into the dwarf planet’s surface, kicking up water ice that then landed in the craters and stayed there.
The presence of water ice in the craters is exciting because the same observations have been made on other bodies in the solar system, including Mercury and the Moon. This finding has important implications for future space travel, since knowing where to find sources of water will be critical for refueling astronauts’ bodies as well as their spaceships during extended missions.