Building blocks of life found on the dwarf planet Ceres
Organic molecules, consisting primarily of carbon and hydrogen and small amounts of other elements, are widely regarded as essential ingredients for life. On Earth, these compounds form the basic building blocks of all living organisms.
Over the last few decades, scientists have discovered similar molecules on distant objects in the solar system, including trans-Neptunian bodies, comets, and far-flung asteroids.
Because these entities are believed to be largely unchanged since the solar system’s birth, many researchers suggest that the building blocks of life might have been present from the start, potentially traveling to the inner regions of the solar system later on.
Organic deposits on the planet Ceres
In a recent study, a team of scientists set out to determine whether the dwarf planet Ceres, situated within the asteroid belt between Mars and Jupiter, contains previously uncharted deposits of organic material.
Because Ceres orbits in a region neither distinctly part of the inner nor the outer solar system, it has sparked interest regarding the origins of its organic elements: Did they form locally, or did they arrive from somewhere else?
The scientists examined the entire surface of Ceres for organic matter, focusing on aliphatic hydrocarbons – chain-like compounds formed when water interacts with rock over long periods.
Earlier studies hinted that such compounds might be scattered across Ceres, prompting researchers to delve deeper into their precise locations and geological contexts.
Dawn mission data
NASA’s Dawn spacecraft reached Ceres in March 2015 and spent about three and a half years mapping the dwarf planet’s surface with a sophisticated camera system and spectrometer.
By observing how the brightness of reflected light changes with different wavelengths, scientists can infer the presence of organic materials.
Dawn’s spectrometer, which splits light into numerous wavelengths, confirmed that these substances belong to the category of aliphatic hydrocarbons, though it could not identify the exact molecular species.
Locating organic molecules on Ceres
The current study, published in the journal Nature Geoscience, made use of an artificial intelligence system to analyze Dawn’s data. The researchers wanted to locate all possible sites of aliphatic hydrocarbons across Ceres and compare them with the dwarf planet’s geological features.
“Sites of such organic molecules are actually rare on Ceres, and devoid of any cryovolcanic signatures,” said Ranjan Sarkar, the study’s first author from the Max Planck Institute for Solar System Research (MPS).
The majority of these deposits appear around the large Ernutet crater in Ceres’ northern hemisphere, though three outliers exist farther away. Two of the patches had not been previously identified.
Martin Hoffmann from MPS elaborated on what the team found. “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.”
Rethinking cryovolcanism as a source
Ceres has long been recognized as a cryovolcanic body, containing a subsurface reservoir of salty water (or brine) that has been seeping up to the surface in certain locations.
This process, known as cryovolcanism, initially seemed like a plausible mechanism for delivering organics to the surface from the dwarf planet’s interior.
“Of course, the first assumption is that Ceres’ unique cryovolcanism has transported the organic material from the interior of the body to the surface. But our results show otherwise,” said Andreas Nathues, head of the Dawn camera team at MPS.
Organic-rich deposits, it appears, do not coincide with regions of cryovolcanic activity. Where cryovolcanic evidence is present, organics are conspicuously absent – and where organics lie, there is no clear sign of volcanic or tectonic features.
This striking mismatch undermines the idea that cryovolcanic processes delivered these compounds from within.
Building blocks of life on Ceres
Instead, the researchers propose that impacts from one or more asteroids in the outer asteroid belt brought the organic materials to Ceres.
Simulations suggest these particular outer belt asteroids frequently collide with Ceres at relatively modest speeds, generating only mild heat. Under such gentle conditions, organics can survive the impact without being destroyed.
“However, the organic deposits that have been reliably detected with Dawn so far likely do not originate Ceres itself,” Nathues explained.
He added that Dawn’s instruments cannot detect all organic compounds, leaving open the possibility that some might have formed within Ceres’ own subsurface ocean and perhaps even reached the surface.
Future exploration of the planet Ceres
Ultimately, the study hints that Ceres may host different populations of organic molecules – some introduced by asteroid collisions, others potentially produced within its interior.
To confirm the latter, the research team advocates for a future lander mission capable of directly sampling Ceres’ subsurface.
Such a mission would provide definitive answers about whether Ceres has been generating organic compounds within its hidden ocean – and whether that process continues today.
Understanding how and where these materials originated could shed light on broader questions about the distribution of life’s building blocks across the Solar System.
As scientists work toward unraveling the full story of organics on Ceres, the study’s findings underscore the complexity of planetary surfaces and the myriad ways cosmic processes can shape them.
By combining advanced data analysis with ambitious exploration, researchers hope to learn more about how life-friendly ingredients form and travel, possibly revealing new clues about the origins of life on Earth and elsewhere.
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