Dwarf planet still growing
NASA data suggests things are far from settled beneath the surface of Ceres. Andrew Masterson reports.
The presence of certain chemical compounds on the surface of the dwarf planet Ceres shows that it is still evolving, researchers have found.
A team led by Filippo Giacomo Carrozzo of Italy’s Istituto di Astrofisica e Planetologia Spaziali used data from a visible-infrared mapping spectrometer on board NASA’s Dawn spacecraft to resolve uncertainties regarding the chemical composition of the dwarf planet, which is the largest object in the asteroid belt, orbiting between Mars and Jupiter.
Previous research and data from Dawn had confirmed the presence of carbonates on the surface of the planet. These are a group of minerals that are extremely diverse and common on Earth, and a defining feature of sedimentary rock. The detection of carbonates on other planets is assumed to be evidence that liquid water was once present.
Carrozzo and colleagues used the Dawn spectrometer data to better map the presence of carbonates. They did this by measuring absorption bands – wavelengths characteristic of particular compounds – to build a map of chemical distribution across the surface.
However, the researchers also report the presence of sodium carbonates, particularly a compound called natrite (Na2CO3). This was unexpected, because if Ceres was nothing more than a long-dead ball of rock then these compounds would have evaporated over the past tens of millions of years.
Instead, they are present in kilometre-size areas, especially near impact craters with domes or mounds. Some of the craters, too, show possible floor fractures.
The evidence leads the researchers to conclude that the sodium carbonates are possibly being pushed to the surface from below-ground by rising subsurface fluids.
Carrozzo and his colleagues suggest therefore that the kilometre-wide patches formed only within the past few million years, and that the process of their gradual evaporation is still underway. The story of Ceres, whatever else it might be, is certainly not finished.