New evidence from NASA suggests that a dwarf planet may have harbored the right conditions to support life in the past.
According to findings published following studies from NASA’s Dawn mission which ended in 2018, the dwarf planet named Ceres once possessed a combination of subterranean water, organic molecules, and, crucially, a long-lasting source of chemical energy.
Although it is now cold, the research shows that Ceres hosted a deep, long-lived energy source that may have maintained habitable conditions in the past.
The Dawn mission proved 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 the liquid was an enormous reservoir of brine, or salty water, just below the surface.
The mission also revealed evidence that Ceres has organic material in the form of carbon molecules that is essential to support microbial cells, though not sufficient on its own.
The study was published in Science Advances on August 20, seven years after the mission took place. In that time, 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.
This 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.
Sam Courville, lead author of the study, said: “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.”
Courville led the research at Arizona State University in Tempe, while also working as an intern at NASA’s Jet Propulsion Laboratory in Southern California, which managed the Dawn mission.
During further analyses, the team found undersea environments that in similar conditions, support thriving microbial ecosystems on earth.
While there is no direct evidence of life on Ceres, the researchers say the discovery of “food” – chemical energy sustaining metabolism – in its ancient oceans significantly boosts its status as a once-habitable world.
NASA JPL added, “The Ceres we know today is unlikely to be habitable. It is cooler, with more ice and less water than in the past. There is currently insufficient heat from radioactive decay within Ceres to keep the water from freezing, and what liquid remains has become a concentrated brine.”
“The period when Ceres would most likely have been habitable was between half a billion and 2 billion years after it formed (or about 2.5 billion to 4 billion years ago), when its rocky core reached its peak temperature. That’s when warm fluids would have been introduced into Ceres’ underground water.”