Ceres and Pluto don’t seem to have much in common. Nestled in the asteroid belt between Mars and Jupiter, Ceres is a tiny loner, while Pluto — in the Kuiper Belt at the edge of the solar system — is nearly three times as big and hosts a handful of moons. A mixture of rock and water ice dominates Ceres’ landscape, while methane and nitrogen ices cover Pluto. A thin, hazy atmosphere hangs over Pluto, while astronomers have seen only faint traces of gas above Ceres. The worlds are so dissimilar that planetary scientist Steve Desch says he is one of only a handful of researchers familiar with both.
But look a little closer, and it turns out the dwarf planets aren’t all that different. New traces of ammonia on Ceres hint at a much closer relationship between the pair. Large depressions mar the surface of each, and both feature icy volcanoes possibly powered by liquid beneath the surface. In fact, astronomers are beginning to consider them twins, albeit fraternal, born in the same place at the same time but separated almost immediately after birth. Their differing adult features reflect their adopted environments.
One more commonality: NASA spacecraft visited both worlds in 2015 — New Horizons flew past Pluto and Dawn began orbiting Ceres. It’s thanks to those missions that we have all this new data in the first place. “If you took a Pluto-like body and put it in the asteroid belt, it would probably look a lot like Ceres,” says astronomer Will Grundy, a co-investigator for New Horizons.
Separated at Birth It turns out that might actually be the case, with Ceres originally starting out nearer to Pluto, before getting shoved around by the bigger planets.
