“Ceres –the only dwarf planet in the inner Solar System–has gained a pivotal role in assessing the origin, evolution and distribution of organic species across the inner solar system,” said Southwest Research Institute scientist Simone Marchi, about high abundance of carbon on Ceres’ near surface, which could be due to an excess of organic matter, possibly formed locally due to water-rocks chemistry.”One has to wonder about how this world may have driven organic chemistry pathways, and how these processes may have affected the make-up of larger planets like the Earth.”
In 2018, a team led by Southwest Research Institute concluded that the surface of dwarf planet Ceres is rich in organic matter. Data from NASA’s Dawn spacecraft indicated that Ceres’s surface may contain several times the concentration of carbon than is present in the most carbon-rich, primitive meteorites found on Earth.
“Like a Chemical Factory” ––Complex Internal Evolution
“A key difference between Ceres and other main belt asteroids,” wrote Marchi in an email to The Daily Galaxy, “is their sizes. Ceres’ large size would have allowed it to retain internal heat for longer, resulting in a more complex internal evolution. Meteorites come from smaller asteroids that would have rapidly cooled with limited chemical evolution.”
“Ceres is like a chemical factory,” observed Marchi. “Among inner solar system bodies, Ceres’ has a unique mineralogy, which appears to contain up to 20 percent carbon by mass in its near surface. Our analysis shows that carbon-rich compounds are intimately mixed with products of rock-water interactions, such as clays.”
“Ceres’ composition is very complex,” Marchi told The Daily Galaxy. “It speaks to chemical interactions between briny waters and rocks to produce compounds that are rare on asteroids. Among these, we find silicates that contain nitrogen and hydrogen (derived from ammonia), carbonates, and organics. While some of these compounds are found in meteorites, Ceres seems to have them in substantially higher concentrations.”
Similar to the Early Earth
“Similar processes would have also taken place on the early Earth. But the early Earth also accreted large asteroids, some of which could have come from the outer solar system after been scattered among the terrestrial planets,” explains Marchi. Some of them could have undergone Ceres-like chemical evolution, and so they could have deposited their budget of complex compounds to the early Earth.”
Ceres is believed to have originated about 4.6 billion years ago at the dawn of our solar system. Dawn data previously revealed the presence of water and other volatiles, such as ammonium derived from ammonia, and now a high concentration of carbon. This chemistry suggests Ceres formed in a cold environment, perhaps outside the orbit of Jupiter. An ensuing shakeup in the orbits of the large planets would have pushed Ceres to its current location in the main asteroid belt, between the orbits of Mars and Jupiter.
Geophysical, compositional, and collisional models based on Dawn data revealed that Ceres’ partially differentiated interior has been altered by fluid processes. Dawn‘s Visible and Infrared Mapping Spectrometer has shown that the overall low albedo of Ceres” surface is a combination of rock-water interaction products such as phyllosilicates and carbonates and a significant amount of spectrally neutral darkening agents, such as an iron oxide called magnetite.
Because Dawn‘s Gamma Ray and Neutron Detector limits magnetite to only a few percent by mass, the data point to the presence of an additional darkening agent, probably amorphous carbon, a carbon-rich organic material. Interestingly, specific organic compounds have also been detected near a 31-mile-wide impact crater named Ernutet, giving further support to the widespread presence of organics in Ceres’ shallow subsurface.
The study also finds that 50% – 60% of Ceres’ upper crust may have a composition similar to primitive carbonaceous chondrite meteorites. This material is compatible with contamination from infalling carbonaceous asteroids, a possibility supported by Ceres’ battered surface.
“Our results imply that either Ceres’ accreted ultra-carbon-rich materials or that carbon was concentrated in its crust,” said Marchi. “Both potential scenarios are important, because Ceres’ mineralogical composition indicates a global-scale event of rock-water alteration, which could provide conditions favorable to organic chemistry.”
A Relic Ocean World
Ceres appears to be a relic ocean world according to data collected by NASA’s Dawn spacecraft as well as persistently geologically active world. Recently exposed brines on Ceres make it officially an ‘ocean world’ (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)(GIPHY)
Scientists are still unpacking and analyzing the data captured by NASA’s Dawn probe from orbit from 2015 to 2018. “Tantalizing studies in the past few years suggest there’s an ocean sitting 25 miles below the surface, and could stretch for hundreds of miles,” reports the MIT Technology Review. “It would almost certainly be extremely salty—which would keep the water from freezing even well below 0°C.”
Editor’s Note: Simone Marchi is the author of Colliding Worlds, published by Oxford University Press about the cosmic encounters that shape the planets of our solar system, and indeed life itself. Join Dr. Simone Marchi in this YouTube video as he explores the story of massive collisions in space, and how they influenced everything from the creation of the Moon to the evolution of life on Earth.
Image credit: Shutterstock License