Dwarf planet Ceres may be getting organic matter from space objects

Ceres is a dwarf planet, the largest object in the asteroid belt. It was explored a few years ago by the Dawn spacecraft. Scientists have recently concluded from the data obtained from it that there is a lot of organic matter on the object, which comes from outside.

Ceres. Source: phys.org

Organics on Ceres

Organic material found at several locations on the surface of the dwarf planet Ceres is likely exogenous in origin. It may have been brought in by asteroids from the outer asteroid belt.

In the journal AGU Advances, a team of researchers led by the Max Planck Institute for Solar System Research (MPS) in Germany presents the most comprehensive analysis to date of this enigmatic material and its geologic context. For this purpose, the team first used artificial intelligence to analyze observational data from NASA’s Dawn spacecraft. 

According to the study, the dwarf planet’s unique cryovolcanism, in which salty brine rises from the interior of the body to the surface, is not responsible for the organic deposits discovered to date. These new findings help us understand where and how habitable conditions in the Solar System might have arisen.

Organic molecules are one of the necessary components of habitable worlds. On Earth, compounds of carbon, hydrogen and, in smaller quantities, other elements form the basic building blocks of all living things. In recent years, researchers have discovered such molecules at great distances from the Sun: on trans-Neptunian objects, comets, and distant asteroids.

These bodies are thought to be mostly unaltered remnants from the early days of the Solar System. Consequently, the building blocks of life may have been part of their “basic configuration” from the beginning and may have only gotten to the interior of the Solar System later.

For this study, scientists searched for previously unknown deposits of organic material on the dwarf planet Ceres. Due to its location in the middle of the asteroid belt between the orbits of Mars and Jupiter, this body does not belong to either the inner or outer Solar System. According to preliminary research, this place might even have been its homeland. Therefore, scientists are interested in the origin of Ceres’ organic components. Did they originate locally in the asteroid belt? Or did they arrive later?

Finding organics from afar

Evidence of deposits of organic material was found early in the Dawn mission. The Dawn spacecraft reached Ceres in March 2015 and accompanied it for about three and a half years. During this time, the scientific camera system and spectrometer on board scanned the entire surface of the dwarf planet.

Potential areas of organic material can be detected from the camera data: the brightness of light reflected from these areas increases markedly with increasing wavelength. A spectrometer splits light into many more wavelengths than a camera and therefore can prove or disprove the presence of organics. 

Unfortunately, remote sensing data are insufficient to indisputably identify individual molecule types. However, it is safe to say that the detected sediments consist of organic compounds that have a chain structure. Researchers call such molecules aliphatic hydrocarbons.

The authors of the new study used artificial intelligence to scan the entire surface of the dwarf planet for traces of aliphatic organic molecules. The vast majority of deposits can be found along the edge of or near the large Ernutet crater in the dwarf planet’s Northern Hemisphere. Only three are located at a greater distance from it. Two spots were not previously known. A closer look at the geologic structures where organic material is found allows further conclusions to be drawn.

“At none of the deposits do we find evidence of current or past volcanic or tectonic activity: no trenches, canyons, volcanic domes or vents. Furthermore, there are no deep impact craters nearby,” said Martin Hoffmann of MPS.

Influence of Ceres’ distant neighbors

During the Dawn mission, Ceres turned out to be an unusual, cryovolcanic world. Beneath its surface is a watery brine that has recently seeped to the surface in some places. 

There is no evidence of organic matter at the cryovolcanic activity sites. And where organic compounds have been reliably detected, there is no evidence of depth or surface activity. 

Therefore, the researchers argue that the influence of one or more asteroids from the outer asteroid belt brought organic material. Computer modeling shows that these bodies are among those that have most often collided with Ceres. Because the non-distant neighbors do not gain much speed, only a small amount of heat is generated on impact. Organic compounds can withstand these temperatures.

“Unfortunately, Dawn can’t detect all types of organic compounds,” says Andreas Nathues of MPS, the camera’s team leader. It’s likely that the building blocks of life also formed in Ceres’ underground ocean and may have even reached the surface — or are still doing so.

“However, the organic deposits that have been reliably detected by Dawn so far likely do not originate from Ceres itself,” he explains. Nathues continues by saying that a future lander mission will be needed to detect organic materials from Ceres’ interior.

NASA’s Dawn mission studied two bodies in the asteroid belt at close range: the protoplanet Vesta from 2011 to 2012 and the dwarf planet Ceres from 2015 to 2018. The mission’s science camera system, Dawn Framing Cameras, was designed, built, and operated during the mission under the direction of MPS. The VIR spectrometer was provided by the Italian space agency ASI.

According to phys.org

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