We keep going through revolutions in the way science fiction writers handle asteroids. Discovered in 1801, Ceres and later Pallas (1802) spawned the notion that there once existed a planet where what came to be thought of as the asteroid belt now exists. Heinrich Olbers was thinking of the Titius-Bode law when he suggested this, pointing to the mathematical consistency of planetary orbits implicit in the now discredited theory. Robert Cromie wrote a novel called Crack of Doom in 1895 that imagined a fifth planet blown apart by futuristic warfare, a notion picked up by many early science fiction writers.

Nowadays, that notion seems quaint, and asteroids more commonly appear in later SF either as resource stockpiles or terraformed habitats, perhaps hollowed out to become starships. Nonetheless, there was a flurry of interest in asteroids as home to extraterrestrial life in the 1930s (thus Clark Ashton Smith’s “Master of the Asteroid”), and actually none other than Konstantin Tsiolkovsky wrote an even earlier work called “On Vesta” (1896), where he imagines a technological civilization emerging on the asteroid. Before someone writes to scold me for leaving it out, I have to add that Antoine de Saint-Exupéry’s The Little Prince (1943) assumes an asteroid as the character’s home world.

The Dawn mission that did so much to reveal the surface of Ceres made it clear how cold and seemingly inimical to life this largest of all asteroids seems to be. But even here, there is new speculation about a warmer past and the possibility of at least primitive life emerging under the frigid surface. The reservoir of interior salty water whose surface residue can be seen in Ceres’ reflective regions now appears, via Dawn data, to contain carbon molecules. So we have water, carbon molecules and a likely source of chemical energy here.

Image: Dwarf planet Ceres is shown in these enhanced-color renderings that use images from NASA’s Dawn mission. New thermal and chemical models that rely on the mission’s data indicate Ceres may have long ago had conditions suitable for life. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

The new work from lead author Samuel Courville (Arizona State University) and team is built around computer models of Ceres, looking at its chemistry and thermal characteristics since the early days of the Solar System. The evidence shows that as late as 2.5 billion years ago, the asteroid’s internal ocean was still being heated by radioactive decay of elements deep in the interior, providing dissolved gases carried by upwelling hot water exposed to the rocks in Ceres’ core.

That’s a significant marker, because we know that here on Earth, mixing hot water, metamorphic rock and ocean provides everything life needs. Demonstrating that Ceres once had hydrothermal fluid feeding into its ocean would imply that microbes could have formed there, even if today they are long gone. Today heat from radioactive decay should be insufficient to keep Ceres’ water from turning into a concentrated brine, but the situation several billion years ago was similar to that of many Solar System objects which lack any source of tidal heating because they do not orbit a large planet.

Image: This illustration depicts the interior of dwarf planet Ceres, including the transfer of water and gases from the rocky core to a reservoir of salty water. Carbon dioxide and methane are among the molecules carrying chemical energy beneath Ceres’ surface. Credit: NASA/JPL-Caltech.

From the paper:

Since Ceres is not subject to as many complex evolutionary factors (e.g., tidal heating) as are many other candidate ocean worlds that orbit gas giants, it is an ideal body to study evolutionary pathways relevant to candidate ocean worlds in the ~500- to 1000-km radius range. Being in large numbers, these bodies might represent the most abundant type of habitable environment in the early solar system.

An interesting thought! We can even speculate on how long this window of astrobiological opportunity might have remained open:

From a chemical energy perspective, the most habitable periods for these objects were when the rocky interiors underwent thermal metamorphism. Metamorphism leads to an influx of fluids into the ocean. These fluids could provide a steady source of chemical disequilibrium for several hundred million years. In the case of Ceres, the metamorphic period between ~0.5 and 2 Gyr would have created a potentially habitable environment at the seafloor if the rocky mantle reached temperatures greater than ~700 K. The decreasing temperature of Ceres’s interior over the past ~1 Gyr would likely render it thermodynamically inactive at present.

A sample return mission to Ceres? Such is recommended as a New Frontiers mission in the decadal survey Origins, worlds, and life: a decadal strategy for planetary science and astrobiology 2023–2032 (The National Academies Press, 2022). The document cites the need for samples “…collected from young carbonate salt deposits, typified by those identified by the Dawn mission at Occator crater, as well as some of Ceres’s typical dark materials.”

The paper is Courville et al., “Core metamorphism controls the dynamic habitability of mid-sized ocean worlds—The case of Ceres,” Science Advances Vol. 11 Issue 34 (20 August 2025). Full text.