The dwarf planet Ceres is an unusual world characterized by cryovolcanic activity. However, the organic materials found on its surface are believed to have come from external sources rather than its core. The organic substances discovered in several locations on Ceres likely originated from asteroids impacting the outer asteroid belt.
The organic substances discovered in various regions on Ceres are thought to originate from outside the dwarf planet. These materials may have been delivered by asteroids colliding with Ceres from the outer asteroid belt. A team of researchers, led by the Max Planck Institute for Solar System Research (MPS) in Germany, has conducted a thorough analysis of this enigmatic material and its geological setting, as reported in the journal AGU Advances. For the first time, artificial intelligence was utilized to examine data gathered by NASA’s Dawn spacecraft. The study reveals that Ceres’ distinctive cryovolcanism—which involves salty brine emerging from below the surface—is not responsible for the organic materials found on the surface. These new insights contribute to our understanding of how and where conditions suitable for life might have emerged in our Solar System.
Organic molecules are essential for life as we know it. On Earth, the compounds made up of carbon, hydrogen, and, to a lesser extent, other elements form the fundamental components of all living organisms. In recent years, scientists have detected these molecules at great distances from the Sun on trans-Neptunian objects, comets, and distant asteroids. These celestial bodies are considered to be largely unaltered remnants from the early Solar System, indicating that the components essential for life may have been part of their initial formation and could have only reached the inner Solar System later on.
For this study, the researchers sought to identify previously unknown deposits of organic materials on Ceres. Situated in the middle of the asteroid belt between Mars and Jupiter, Ceres does not clearly belong to either the inner or the outer Solar System, and some theories suggest this may even be its place of origin. Consequently, scientists are keen to learn about the origins of the organic materials found on Ceres. Did these materials form locally within the asteroid belt, or were they delivered at a later time?
Scanning for Organics from a Distance
Early in the Dawn mission, evidence of organic material was detected. The Dawn spacecraft reached Ceres in March 2015 and studied it for over three years. During this period, its scientific camera and spectrometer analyzed the entire surface of the dwarf planet. Specific patches of organic material can be identified through the camera data, where the brightness of the reflected light significantly increases with wavelength. The spectrometer can analyze light across a broader range of wavelengths, allowing researchers to confirm the presence of organic materials. However, remote observations are insufficient to identify specific types of molecules with complete certainty. Nonetheless, it is clear that the identified deposits contain organic compounds characterized by chain-like structures, known as aliphatic hydrocarbons.
The authors of this study employed artificial intelligence to meticulously search the surface of Ceres for traces of aliphatic organic molecules. “These types of organic molecules are quite rare on Ceres, and none of them show any signs of cryovolcanic activity,” explains first author Ranjan Sarkar from MPS, highlighting the findings. Most of the organic deposits are located on or near the large Ernutet crater in the northern hemisphere, with only three farther away. Two of these patches were previously unidentified. A detailed examination of the geological features surrounding these organic material locations leads to further conclusions. “At none of these sites do we see evidence of past or present volcanic or tectonic activity: no trenches, canyons, volcanic domes, or vents, and there are no nearby deep impact craters,” says Martin Hoffmann from MPS.
Cosmic Impacts from Distant Neighbors
Ceres has emerged as a remarkable, cryovolcanic world, revealing a hidden brine layer beneath its surface, which has been seeping out in certain areas until relatively recently. “The initial assumption is that Ceres’ unique cryovolcanism has brought organic materials from its interior to the outside,” comments Andreas Nathues from MPS, head of the camera team. “However, our findings suggest otherwise.” At the sites known for cryovolcanic activity, the presence of organic matter has not been proven. Likewise, in locations where organic compounds have been definitively identified, no evidence of deep or surface geological activity is observed.
The researchers contend that the organic materials were likely introduced by asteroids crashing into Ceres from the outer asteroid belt. Computer simulations indicate that these asteroids frequently collide with Ceres. Given that these relatively nearby objects do not travel at high speeds, the heat generated during impacts is limited, allowing organic compounds to withstand such temperatures.
“Regrettably, Dawn is not capable of detecting all types of organic compounds,” points out Andreas Nathues. It is quite possible that life-building blocks could also have formed in Ceres’ underground ocean and might have reached the surface—possibly still doing so. “However, the organic deposits that have been reliably identified thus far likely do not come from Ceres itself,” he explains, stressing that a future lander mission would be necessary to obtain organic materials from Ceres’ interior.
About the Mission
NASA’s Dawn mission closely studied two objects in the asteroid belt: the protoplanet Vesta from 2011 to 2012 and the dwarf planet Ceres from 2015 to 2018. The scientific camera system, known as the Dawn Framing Cameras, was developed, constructed, and managed under the MPS’s leadership, while the VIR spectrometer was provided by the Italian Space Agency ASI.
