Ceres, the Celebrity of the Asteroid Belt

Despite comprising almost a third of the asteroid belt’s total mass, Ceres is often left out of dwarf planet discussions. However, Ceres is actually pretty unique and could potentially support life in the future. Because of its relative closeness compared to the likes of Pluto, it was the first dwarf planet to be visited by a spacecraft, called Dawn. While Ceres looks like many asteroids, especially those called C-type asteroids, Ceres contains much more water than anticipated. In fact, it could possibly be almost 25% water, which is more than available on Earth. It also contains ammonia on its surface which is characteristic of objects outside of the ice line. In these ways, Ceres is much more similar to a Kuiper Belt object than an asteroid belt one. There are plenty of theories suggested to explain how these characteristics formed in the asteroid belt, but some scientists believe Ceres actually originated outside the orbit of Saturn. During the early solar system formation, it could have migrated to its current location as giant planets shifted. Learn more about the migration theory here.

Another unique factor separating Ceres from other asteroids is evidence that Ceres was geologically active despite its small size. Ceres could not generate heat like other terrestrial planets or through tidal friction like many giant moons. Instead, it is thought that Ceres was initially cold, and the radioactive decay of elements like uranium and thorium heated the planet up for a period of time before cooling again. This process is called radiogenic heating, and its natural instability would produce unique features across the surface of Ceres. For example, there is a large plateau on one hemisphere with localized fractures that were lacking on the other hemisphere. Physicists simulated this with a model of localized instability on one hemisphere, and the fractures match those observed by the Dawn spacecraft. Read more about the model here. 

This geological activity could have created ice volcanoes which could produce the water vapor found in its thin atmosphere. Additionally, layers of ice could shift and erase large craters while perhaps even a layer of water ice exists below the crust. Because of this, some astronomers are hoping for a rover mission to Ceres to take samples and gather information about the possibility of sustaining life not so far away from home.

An artist’s rendition of Cere’s possible layers is shown below.

Source: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA