Ceres is a key object in understanding the evolution of small bodies and is the only dwarf planet to have been orbited by a spacecraft, NASA’s Dawn mission. Dawn data paint an inconclusive picture of Ceres’ internal structure, composition and evolutionary pathway. New research shows that a crust with nearly 90% ice near the surface, which gradually decreases to 0% at 117 km depth, simultaneously matches the Dawn observations. This crustal structure results from a frozen ocean that became more impurity rich as it solidified top-down. Therefore, the Dawn data are consistent with an icy Ceres that evolved through freezing of an ancient, impure ocean.
“Ceres is the largest object in the asteroid belt, and a dwarf planet. I think sometimes people think of small, lumpy things as asteroids (and most of them are!), but Ceres really looks more like a planet,” said Purdue University researcher Mike Sori.
“It is a big sphere, diameter 950 km or so, and has surface features like craters, volcanoes, and landslides.”
“We think that there’s lots of water-ice near Ceres surface, and that it gets gradually less icy as you go deeper and deeper.”
“People used to think that if Ceres was very icy, the craters would deform quickly over time, like glaciers flowing on Earth, or like gooey flowing honey.”
“However, we’ve shown through our simulations that ice can be much stronger in conditions on Ceres than previously predicted if you mix in just a little bit of solid rock.”
This discovery is contradictory to the previous belief that Ceres was relatively dry.
The common assumption was that Ceres was less than 30% ice, but Sori’s team now believes the surface is more like 90% ice.
“Our interpretation of all this is that Ceres used to be an ocean world like Europa (one of Jupiter’s moons), but with a dirty, muddy ocean,’” Dr. Sori said.
“As that muddy ocean froze over time, it created an icy crust with a little bit of rocky material trapped in…
Read the full article here