Dwarf planet Ceres: Hydrocarbons probably came from outside

The organic material on the dwarf planet Ceres is probably of extra-Ceresian origin: a recent study concludes that asteroids from the outer asteroid belt that crashed into the dwarf planet brought it with them.

A team led by the Max Planck Institute for Solar System Research (MPS) in Göttingen has comprehensively analyzed the data collected from the dwarf planet by the Dawn space probe. Artificial intelligence (AI) was used for the first time. 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 size in the middle asteroid belt between the orbits of Mars and Jupiter. This makes it significantly larger than the other asteroids. Another special feature is the large amount of water and salt. In some places, brine from ice volcanoes rises to the surface.

Do the organic molecules come from the interior of Ceres?

During measurements with the spectrometer, Dawn found evidence of organic molecules in several craters on the dwarf planet, namely aliphatic hydrocarbons. These are organic molecules in which carbon atoms form long, unclosed chains. Until now, researchers had assumed that the hydrocarbon compounds were formed in the interior of Ceres and brought to the surface by the ice volcanoes.

The MPS team used AI to examine the entire surface of Ceres for the aliphatic molecules. The result was that sites of organic molecules are rare, said Ranjan Sarkar, first author of the paper in the journal AGU Advances. Above all: “They do not show typical features of cryovolcanism.”

Organic molecules in the outer asteroid belt

This means that the organic molecules, which are considered to be the basic building blocks of life, must have come to the dwarf planet from outside. The team suspects that asteroids from the outer asteroid belt brought them there. Organic compounds have already been found on these celestial bodies, which are considered to be largely unaltered remnants from the early days of the solar system.

As these asteroids are not traveling too fast, comparatively little heat is generated when they hit Ceres. Organic compounds can survive these temperatures.

However, the team does not want to rule out the possibility that hydrocarbons were also formed in Ceres' underground ocean and may even have reached the surface. “However, the organic deposits that have been reliably detected by Dawn so far probably do not originate from Ceres itself,” said Andreas Nathues from the MPS. But Dawn has “not been able to detect all types of organic compounds”. A future lander mission would be needed to detect organic material from the interior.

(wpl)