The organic material on the dwarf planet Ceres is likely of extraterrestrial origin. A recent study concludes that asteroids from the outer asteroid belt, which impacted the dwarf planet, brought it there. A team led by the Max Planck Institute for Solar System Research (MPS) in Göttingen thoroughly analyzed the data collected by the Dawn spacecraft from the dwarf planet. For the first time, artificial intelligence (AI) was used in this analysis. Dawn arrived at Ceres in March 2015 and collected data until it ran out of fuel in November 2019.
Ceres is a dwarf planet about 960 kilometers in diameter, located in the middle of the asteroid belt between the orbits of Mars and Jupiter. It is significantly larger than other asteroids. A notable feature of Ceres is its large amount of water and salt. In some places, brine from ice volcanoes reaches the surface.
Did the organic molecules originate from within Ceres? During measurements with the spectrometer, Dawn found evidence of organic molecules in several craters on the dwarf planet, specifically aliphatic hydrocarbons. These are organic molecules where carbon atoms form long, open chains. Until now, research assumed that these hydrocarbon compounds originated inside Ceres and were brought to the surface by ice volcanoes.
The MPS team used AI to examine the entire surface of Ceres for aliphatic molecules. The result was that sites with organic molecules are rare, said Ranjan Sarkar, lead author of the paper in the journal AGU Advances. Importantly, “they do not show typical features of cryovolcanism.”
This suggests that the organic molecules, considered fundamental building blocks for life, must have come to the dwarf planet from outside. The team suspects that asteroids from the outer asteroid belt brought them there. These celestial bodies, considered largely unchanged remnants from the early solar system, have already been found to contain organic compounds.
Since these asteroids do not travel very fast, an impact on Ceres generates relatively little heat. These temperatures can be withstood by organic compounds. However, the team does not want to rule out the possibility that hydrocarbons also formed in Ceres’ underground ocean and possibly even reached the surface. “The organic deposits that have been reliably detected with Dawn so far probably do not originate from Ceres itself,” said Andreas Nathues from MPS. However, Dawn was “not able to detect all types of organic compounds.” To prove organic material from the interior, a future landing mission would be necessary.
In conclusion, the study suggests that the organic materials on Ceres likely have an external origin, brought by asteroids from the outer asteroid belt. While there is a possibility that some organic materials could have originated from within Ceres, the current evidence points towards an extraterrestrial source. Future missions may provide more insights into the origins of these organic compounds and their implications for the study of life in the solar system.