Hexbyte – Tech News – Ars Technica |
What might once have been a ridge along its equator is now tilted 36° off.
Prior to our visit to the dwarf planet Ceres, we knew that it had a density about twice that of water. Considering it likely has a rocky core, that means much of its outer crust is likely to be water. Since water is pretty malleable at the temperatures we’d expect to prevail on Ceres, there were some expectations that any features on the planet had long since flattened out as the ice they were made of flowed downwards as it does in glaciers.
This turned out to be anything but the case, as Ceres is covered in craters, ridges, and the remains of what appear to be ice volcanoes. All of which suggests that the crust is far more rigid than we thought and has a composition that’s more complex than simply water with some dust mixed in.
Now, a researcher named Pasquale Tricarico has analyzed the distribution of material on Ceres and found that it is consistent with the densest material having caused the relocation of the planet’s equator. He suggests that a series of ridges that ring the dwarf planet represent the former equator, which would mean that Ceres tipped over on its side at some point early in its history.
The simplest evidence that there are potential oddities in Ceres’ crust comes from a simple mapping of its density. Ceres’ average density is about two grams per cubic centimeter, but the crust can be below 1.7 g/cm>3 and range up to above 2.3 g/cm>3. So there are a lot of spatial differences in the distribution of material in the crust. Mapping that out on the surface of Ceres shows that the most dense regions—and therefore the ones likely to be the most massive—are generally located along the equator. This includes the likely cryovolcano Ahuna Mons.
This makes sense from what we know of a body’s rotation, which would naturally align so the heaviest material is the farthest out from the axis of rotation. Typically, this would happen naturally during planet formation. But if planets are geologic