New research on those bright spots inside Occator Crater on Ceres show they’re very young and may still be oozing briny lava. Scientists at the Max Planck Institute for Solar System Research (MPS) have closely examined the crater’s bright central pit domed by a deposit of mineral salt left over when brines rose to the surface from below. The water would have quickly vaporized away, leaving behind a white, salty coating like the what salt stains on asphalt after the plow’s been through and the ice evaporates.
By making crater counts in the region, astronomers were able to estimate the age of both Occator and the salt deposits. They do this by noting that more heavily cratered areas are much older — they’ve been under bombardment for a longer time — than fresher, newer landscapes that have few to no craters. Occator’s about 30 million years old, but the salt is only about 4 million years old. That’s practically brand new considering that Ceres and many of its formed 4.5 billion years ago.
The scientists also point out that the white coating is rich in carbonates, a mineral that forms when carbon dioxide interacts with water. Ceres has plenty of the wet stuff to spare with an estimated 30% of the dwarf planet made of water ice. Much of that lies just beneath the crust, insulated by rock for billions of years.
The dome and other bright patches seen in the photo likely originate from that subsurface layer. The huge impact that blasted out Occator Crater 30 million years ago would have heated warmed and melted the ice which then bubbled and boiled through fractured rock to the surface as the brine equivalent of lava. We don’t know if this was a one-time event or whether it happened in episodes. But it may still be happening to this day.
NASA’s Dawn spacecraft photographed a haze layer at the bright spots that waxes and wanes according to the time of day, and Europe’s Herschel spacecraft detected water vapor spewing off Ceres in 2014, suggested geological activity. If only we could send a lander to Ceres to touch down on the brightest spot, take a sample, hang around and wait for the haze to gather.