NASA scientists have unveiled evidence that the dwarf planet Ceres—the largest body in the asteroid belt between Mars and Jupiter—may have harboured the right conditions to support life in its distant past.

According to findings published following studies from NASA’s Dawn mission, Ceres once possessed a combination of subterranean water, organic molecules, and, crucially, a long-lasting source of chemical energy.

The dwarf planet is cold now, but the new research paints a picture of Ceres hosting a deep, long-lived energy source that may have maintained habitable conditions in the past.

Science data from NASA’s Dawn mission, which ended in 2018, previously showed that the bright, reflective regions on Ceres’ surface are mostly made of salts left over from liquid that percolated up from underground.

Later analysis in 2020 found that the source of this liquid was an enormous reservoir of brine, or salty water, below the surface. In other research, the Dawn mission also revealed evidence that Ceres has organic material in the form of carbon molecules – essential, though not sufficient on its own, to support microbial cells.

In the study, published in Science Advances on August 20, the authors built thermal and chemical models mimicking the temperature and composition of Ceres’ interior over time.

They found that around 2.5 billion years ago, Ceres’ subsurface ocean may have had a steady supply of hot water containing dissolved gases travelling up from metamorphosed rocks in the rocky core.

The heat came from the decay of radioactive elements within the dwarf planet’s rocky interior that occurred when Ceres was young – an internal process thought to be common in our solar system.

“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. So it could have big implications if we could determine whether Ceres’ ocean had an influx of hydrothermal fluid in the past,” said Sam Courville, lead author of the study. Now based at Arizona State University in Tempe, he led the research while working as an intern at NASA’s Jet Propulsion Laboratory in Southern California, which also managed the Dawn mission.

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