Icy dwarf planet Ceres may have a warmer core, scientists found.
Researchers found jumbled icy and rocky zones within the planet's interior, which suggests that Ceres could still be warmed by radioactive material at its heart, Space.com reports.
Ceres is the closest dwarf planet to Earth and the biggest member of the asteroid belt located between Mars and Jupiter, measuring about 585 miles in diameter. Based on previous analysis using ground and space telescopes, the dwarf planet was found to be not as dense as other large asteroids, which suggests that Ceres may not be made purely of rock but a mixture of ice and rock.
According to the researchers, a key parameter to understanding Ceres' internal structure involved determining its "moment of inertia," or how easy or difficult it is for the planet to spin. This property is based on the principle that the lower the moment of inertia, the denser the material is in a body's center.
To determine the moment of inertia, the scientists used the gravity-field data that NASA's Dawn spacecraft gathered from its close encounter with Ceres. According to the researchers, data showed that Ceres could only be partially differentiated, with an interior made of rock overlaid by a volatile-rich shell composed of a mixture of rocky, icy and salty material, with a thickness of 70 to 190 kilometers (43.5 to 120 miles).
"The partial differentiation suggests that Ceres was hot at one point, but it did not fully separate the water and other volatiles from its rocky components," Ryan Park, planetary scientist at NASA's Jet Propulsion Laboratory in Pasadena, California and lead author of the study, told Space.com.
The researchers also suggested that Ceres' insides could still be warm, indicating that the heat from radioactive material is keeping the planet's interior warm. According to the researchers, this discovery was a bit of a surprise, as previous studies suggested that a body as small as Ceres should have cooled off long ago.
Understanding the structure of Ceres could provide insight into how dwarf planets and other asteroids had evolved over time.
The study findings were detailed online in the journal Nature.