Remnants of an ancient water ocean are buried beneath the icy crust of dwarf planet Ceres — or, at least, lingering pockets of one. That’s the tantalizing find presented August 10 by scientists working on NASA’s Dawn mission. Their research was laid out in a series of papers published in Nature.
By far, Ceres is the largest object in the asteroid belt, which girdles the inner planets between Mars and Jupiter. But unlike its rockier neighbors, Ceres is a giant ice ball. It holds more water than any world in the inner solar except for Earth. That knowledge had long led some astronomers to suspect Ceres may have once had a subsurface ocean, which is part of the reason NASA sent the Dawn spacecraft there.
However, some models predicted that Ceres' ocean would have frozen long ago, forming the world’s thick, icy crust.
Now, after five years studying a series of strange surface features around recently-formed craters, astronomers believe they’re seeing signs of a large, subsurface body of briny liquid. Variations in Ceres’ gravitational field back that up, implying that the underground reservoir of salty water may stretch horizontally beneath the ice for hundreds of miles and reach depths of roughly 25 miles (40 kilometers).
“Past research revealed that Ceres had a global ocean, an ocean that would have no reason to exist [still] and should have been frozen by now,” study co-author and Dawn team member Maria Cristina De Sanctis of the National Institute of Astrophysics in Rome tells Astronomy. ”These latest discoveries have shown that part of this ocean could have survived and be present below the surface.”
