Is Ceres Still Spewing Haze, Oozing Brine?

This series of photos show how haze forms and disappears around the white spots in Occator Crater on Ceres during the day. The view at noon (a) shows a white haze that nearly fills the crater’s floor. At dusk (b), the haze has disappeared completely. The bottom photos (c,d) shows changes in the haze as viewed in profile. 450 seconds separate the images c and d. Credit: NASA/JPL/CALTECH/UCLA/MPS/DLR/IDA

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.

Closeup of the bright spots in Occator Crater. The brightest (left), a mound-shaped feature named Cerealia Facula, shows almost no craters, an indication of just how fresh the salts and carbonates are that percolated up from below the crust. Credit: NASA/JPL-Caltech

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.

This photo of the edge of dwarf planet Ceres shows a section of the northern hemisphere that prominently features Occator Crater and intriguing brightest areas. At 57 miles (92 km) wide and 2.5 miles (4 km) deep, Occator displays evidence of recent geologic activity. Credit: NASA/JPL-Caltech

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.

This panel shows the crater and bright spots as seen from many angles taken by the orbiting Dawn spacecraft. Credit: NASA/JPL-Caltech

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.

This photo well captures how dark the surface of Ceres is. The dwarf planet reflects only 9% of the sunlight striking it. In contrast, the salty spots in Occator Crater reflect 40% of the light they receive from the sun. The Earth’s reflectance is around 30% for comparison. The bump at the right edge is Ahuna Mons, the tallest feature on Ceres and believed to be a volcano composed of ice. Credit: NASA/JPL-Caltech

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.