How do we look inside a planet? Well, in the absence of having some futuristic super-powerful drill, we have to use more indirect methods to do so.
And that’s exactly what scientists have done to peer inside the dwarf planet Ceres. By sending and receiving signals to NASA's orbiting Dawn spacecraft, they have been able to map the variations in the gravity of Ceres for the first time, hinting at what it is made of. The findings are published in the journal Nature.
Using this technique, the team of scientists from NASA’s Jet Propulsion Laboratory (JPL) in California found that Ceres has distinct layers. The densest of these is its core, but the scientists also think it has a region of low-density materials such as water ice located nearer to its surface. However, the difference between the layers is less well defined than on worlds like Earth.
“We have found that the divisions between different layers are less pronounced inside Ceres than the Moon and other planets in our Solar System," said the study’s lead author Ryan Park from JPL in a statement. "Earth, with its metallic core, semi-fluid mantle and outer crust, has a more clearly defined structure than Ceres."
Park suggests that water and other light materials may have separated from the rock during a “heating phase” early in the history of Ceres. He added to Space.com that this may be due to radioactive material inside Ceres, and that the dwarf planet’s interior may still be warm, which is somewhat of a surprise.
This all points to Ceres once having water moving beneath its surface in its past, but the dwarf planet never reached the temperatures necessary to form a metallic core like Earth.
Dawn is continuing to orbit Ceres, having been denied a mission to go and visit another asteroid in the asteroid belt. Dawn first entered orbit around Ceres in March 2015, after the spacecraft had visited and studied the protoplanet Vesta – making it the first spacecraft to orbit two separate bodies in the Solar System other than Earth, using its revolutionary ion engine to achieve the feat.
By staying in orbit around Ceres, scientists hope to observe changes on the dwarf planet as it gets nearer to the Sun in its orbit and heats up. Many mysteries remain about Ceres, but for now we at least know a bit more about what’s going on inside it.