The asteroid Ceres is an ancient ocean world that slowly formed into a giant, murky icy orb.

Since Giuseppe Piazzi first observed the first and largest asteroid discovered in our solar system in 1801, astronomers and planetary scientists have pondered the composition of this asteroid/dwarf planet. Its heavily battered and dimpled surface is covered with impact craters. Scientists have long argued that the visible craters on the surface meant that Ceres could not be very icy.

Researchers at Purdue University and NASA’s Jet Propulsion Lab (JPL) now believe that Ceres is a very icy object that may once have been a muddy ocean world. This discovery that Ceres has a dirty ice crust is led by Ian Pamerleau, Ph.D. student, and Mike Sori, assistant professor in Purdue’s Department of Earth, Atmospheric and Planetary Sciences, who published their discoveries in Natural astronomy. The duo and Jennifer Scully, a research scientist at JPL, used computer simulations of how Ceres’ craters deform over billions of years.

“We think there is a lot of water ice near the surface of Ceres and that it becomes progressively less icy as you go deeper and deeper,” Sori said. “People thought that if Ceres was very icy, the craters would deform quickly over time, like flowing glaciers on Earth or like gooey flowing honey. However, we showed through our simulations that ice can be much more resilient in conditions on Earth than expected if you mix in just a little solid rock.”

The team’s discovery contradicts the previous belief that Ceres was relatively dry. The common assumption was that Ceres was less than 30% ice, but Sori’s team now estimates that the surface is instead 90% ice.

“Our interpretation of all this is that Ceres was an ‘ocean world’ like Europa (one of Jupiter’s moons), but with a dirty, muddy ocean,” Sori said. “As this muddy ocean froze over time, it created an icy crust with some rocky material trapped inside.”

Pamerleau explained how they used computer simulations to model how relaxation occurs in Ceres’ craters over billions of years.

“Even solids flow over long periods of time, and ice flows more easily than rock. Craters have deep bowls that produce high stresses which then release to a lower stress state, which which results in a shallower bowl via solid-state flow,” he said. “The conclusion after NASA’s Dawn mission was that due to the lack of relaxed, shallow craters, the crust could not be that icy. Our computer simulations explain a new way in which ice can flow with only a little non-icy impurity mixed in, which would allow a very ice-rich crust to barely flow, even over billions of years. Therefore, we could get an ice-rich Ceres that still fits. to the observed lack of crater relaxation. We tested different crustal structures in these simulations and found that a gradual crust with high ice content near the surface, which slopes down to lower ice with depth, was the best fit. to limit the relaxation of cerian craters.

Sori is a planetary scientist specializing in planetary geophysics. His team is addressing questions about planetary interiors, the connections between planetary interiors and surfaces, and these questions could be answered through spacecraft missions. His work covers 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 little lumpy things as asteroids (and most of them are!), but Ceres is definitely more like to a planet,” Sori said. “It is a large sphere, with a diameter of about 950 kilometers, 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 protoplanets Vesta and Ceres. Although it was launched in 2007, Dawn did not reach Ceres until 2015. It orbited the dwarf planet until 2018.

“We used several observations made with Dawn data to find an ice-rich crust that resisted crater relaxation on Ceres. Different surface features (e.g., pits, domes, and landslides, etc.) suggest that the basement near 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 gravitational data gives a density value very close to that of ice, especially impure ice. We also took the topographic profile of a real complex crater on Ceres and used it to construct the geometry of some of our simulations.

Sori says that because Ceres was the largest asteroid, it was suspected that it could have been any icy object, based on some estimates of its mass made from Earth. these factors made it an excellent choice for a spaceship tour.

“For me, what’s exciting about all of this, if we’re right, is that we have a frozen ocean world quite close to Earth. Ceres could be a valuable point of comparison for the icy moons of the outer solar system that are home to oceans like Jupiter’s moon Europa and Saturn’s moon Enceladus,” Sori said. “Ceres, we believe, is therefore the most accessible icy world in the universe. This makes it an ideal target for future space missions. Some of the bright features we see on the surface of Ceres are the remains of the ocean muddy Ceres, now mostly or entirely frozen, has erupted to the surface so we have a place to collect ocean samples from an ancient ocean world where it’s not too difficult to send a spacecraft. .