This image of Ceres approximates how the dwarf planet’s colors would appear to the eye. This view of Ceres, produced by the German Aerospace Center in Berlin, combines images taken during Dawn’s first science orbit in 2015 using the framing camera’s red, green and blue spectral filters. The color was calculated using a reflectance spectrum, which is based on the way that Ceres reflects different wavelengths of light and the solar wavelengths that illuminate Ceres. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
New research based on data from NASA’s Dawn mission suggests the dwarf planet Ceres may have once possessed a deep, long-lasting energy source capable of sustaining habitable conditions in its ancient past.
The findings, published on Aug. 20 in the journal Science Advances, add a crucial third piece to the puzzle of Ceres’s potential habitability. While the Dawn mission previously confirmed the presence of liquid water (in a subsurface brine reservoir) and essential carbon-based organic molecules — non-biological chemical building blocks for life — this new study identifies a viable, long-term chemical energy source. Though there is no evidence that life ever arose on the dwarf planet, the discovery supports theories that, for a significant period, Ceres had all the necessary ingredients to support microbial organisms.
Ceres is the largest object in the main asteroid belt, a dwarf planet roughly 585 miles (940 kilometers) in diameter. It has long intrigued scientists due to its surprisingly water-rich composition. The dwarf planet is now extremely cold, and any remaining liquid is thought to be a highly concentrated, frigid brine unlikely to support life as we know it. The new findings paint a picture of a much more dynamic and warmer past.
“On Earth, when hot water from deep underground mixes with the ocean, the result is often a buffet for microbes — a feast of chemical energy,” said Sam Courville, planetary scientist and lead author of the study, who led the research at NASA’s Jet Propulsion Laboratory. “So it could have big implications if we could determine whether Ceres’ ocean had an influx of hydrothermal fluid in the past.”
Energy bubbling up from below
The study used sophisticated thermal and chemical models to simulate the evolution of Ceres’s interior over billions of years. The models indicate that heat from the decay of radioactive elements in the dwarf planet’s rocky core could have raised its temperature to more than 550 Kelvin (roughly 530°F). This intense heating would have triggered a process called thermal metamorphism, essentially baking hydrated rocks in the core and forcing them to release hot water rich in dissolved gases like carbon dioxide and hydrogen.
This heated, mineral-laden fluid would have then percolated upward, mixing with the colder global ocean that existed beneath Ceres’s icy shell. This process would have created a powerful chemical imbalance, providing a potential energy source for chemotrophs, organisms that derive energy from chemical reactions. Because this potential habitat was a deep subsurface ocean, locked beneath a thick crust of ice, sunlight would have been unavailable, making chemical energy the only viable option for life instead of photosynthesis.
According to the study, this potentially habitable period on Ceres would have occurred between 2.5 and 4 billion years ago, lasting for hundreds of millions of years as the core reached its peak temperature of 800 Kelvin (980°F).
This warm era did not last forever. The heat was generated by the decay of finite radioactive elements, and as this internal furnace naturally cooled over geologic time, it could no longer sustain the hydrothermal activity. Without the steady supply of hot fluids from the core, Ceres’s subsurface ocean began to cool and eventually freeze, locking away the ingredients for life and ending the dwarf planet’s habitable period.
The three ingredients for life
In short, the study concludes that for a long time, ancient Ceres had the three key ingredients for life as we know it: liquid water, the right chemical building blocks, and a confirmed energy source. This is not evidence that life ever existed on Ceres, but it confirms that a potentially habitable environment with all the necessary conditions was present deep beneath its surface.
The Dawn mission’s ongoing legacy
This new understanding of Ceres’s history is a direct result of NASA’s Dawn mission. Launched in 2007, Dawn became the first spacecraft to orbit two deep-space destinations, studying the asteroid Vesta before arriving at Ceres in 2015. The mission, which concluded in 2018, gathered a trove of data that scientists are still analyzing. Its discovery of bright salt deposits in Occator Crater provided the first concrete evidence of liquid erupting from Ceres’s interior, setting the stage for this latest habitability research.
The implications of the study extend beyond Ceres, suggesting that many other mid-sized, water-rich worlds in the outer solar system could have followed a similar evolutionary path, hosting habitable periods long ago before freezing over.