Ceres changed from ocean world to icy, muddy orb

September 30 () –

Simulations of the deformation of Ceres’ craters over millions of years reveal that this dwarf planet was once a muddy, oceanic world. retains a dirty ice crust.

“We think there is a lot of water ice near the surface of Ceres, and that it gradually becomes less icy as you go further and further down,” explains Mike Sori, associate professor in the Department of Earth, Atmospheric and Planetary Sciences. from Purdue University and co-author of the new research, published in Nature Astronomy.

“People used to think that if Ceres was very icy, the craters would deform quickly over time, like glaciers flowing on Earth, or like viscous honey flowing. However, we have shown through our simulations that the Ice may be much stronger under Ceres conditions than previously predicted if mixed with a little solid rock.”

90 PERCENT ICE SURFACE

The team’s discovery is contradictory to the previous belief that Ceres was relatively dry. The common assumption was that Ceres It had 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,” Sori said. “As that muddy ocean froze over time, “It created an icy crust with some rock material trapped in it.”

Ian Pamerleau, a PhD student and co-author of the study, explained how they used computer simulations to model how crater relaxation occurs on Ceres. over billions of years.

“Even solids flow on long time scales, and ice flows more easily than rock. Craters have deep basins that produce high stresses that then relax to a lower stress state, resulting in a shallower basin.” through solid state flow,” said in a statement.

“The conclusion after NASA’s Dawn mission was that, due to the lack of relaxed, shallow craters, the crust could not be so icy. Our computer simulations account for a new way in which ice can flow with just a little bit of non-ice-derived impurities mixed in, which would allow a very ice-rich crust to barely flow even for billions of years. So we could get an ice-rich Ceres that still matches the lack of relaxation. of craters observed. We tested different crustal structures in these simulations and found that a gradual crust with high ice content near the surface gradually shrinking to lower ice with depth was observed. “the best way to limit the relaxation of Ceres’ craters.”

Sori is a planetary scientist whose focus is planetary geophysics. His team addresses questions about planetary interiors, the connections between planetary interiors and surfaces, and those questions could be resolved with space missions. His work spans many solid bodies in the solar system, from the Moon and Mars to icy objects in the outer solar system.

“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 are!), but Ceres is actually more like a planet “Sori said. “It is a large sphere, about 950 kilometers in diameter, and has surface features such as craters, volcanoes and landslides.”

On September 27, 2007, NASA launched the Dawn mission. This mission was the first and only spacecraft to orbit two extraterrestrial destinations: the protoplanet Vesta and Ceres. Although it launched in 2007, Dawn didn’t arrive at Ceres until 2015. It orbited the dwarf planet until 2018.

“We used multiple observations made with Dawn data as motivation to find an ice-rich crust that resisted crater relaxation on Ceres. Different surface features (e.g. trenches, domes, and landslides, etc.) suggest that “The nearby subsurface of Ceres contains a lot of ice.”Pamerleau said. “The spectrographic data also shows that there should be ice beneath the regolith on the dwarf planet and the gravity data gives a density value very close to that of ice, specifically impure ice. We also took a topographic profile of an actual complex crater on Ceres and we used it to build the geometry for some of our simulations.”

Sori says that because Ceres is the largest asteroid, there was suspicion that it could have been any icy object based on some estimates of its mass made from Earth. These factors made it a excellent option for a space visit.

“For me, the most exciting thing about all of this, if we’re right, is that we have an icy ocean world quite close to Earth. Ceres can be a valuable comparison point for icy moons in the outer solar system that host oceans, like Jupiter.