Data from NASA's Dawn mission has revealed surprising clues. Bright spots on the surface of the dwarf planet Ceres, in the asteroid belt, are actually salt deposits left by briny liquids that once rose from its depths. These discoveries suggest past geological activity more intense than expected.
Organic molecules have been detected in Ceres' soil, indicating the presence of essential ingredients for life. These carbon compounds are fundamental building blocks for living organisms. Their existence on this celestial body opens new perspectives.
Ceres, once considered a dead world, may have hosted conditions suitable for life.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
An energy source would have been necessary to support potential life forms. Computer models show that radioactive decay in Ceres' rocky core could have generated heat billions of years ago. This heat would have fueled hydrothermal activity, potentially creating environments conducive to life.
This hydrothermal activity could have allowed the circulation of liquid water and the formation of nutrients. On Earth, hydrothermal vents host microbial ecosystems without sunlight. Ceres might have offered similar conditions for a limited period.
Today, Ceres is a cold, frozen world, with most of its water in the form of ice. Its window of habitability likely closed long ago. However, this study expands our understanding of potentially habitable environments in the Solar System.
Other icy bodies of similar size, like some moons of Uranus and Saturn, might have followed comparable evolutionary paths. These worlds could have hosted temporary oceans before freezing, offering niches for microbial life in the past.
Representation of Ceres' interior showing water and gas flows from the core.
Credit: NASA/JPL-Caltech What is hydrothermal activity?
Hydrothermal activity refers to the circulation of hot water through rocks, often due to internal heat sources like radioactivity or volcanism. This process can dissolve minerals and transport chemical elements, creating nutrient-rich environments.
On Earth, this activity is observed at underwater hot springs, where water heated by magma rises and interacts with the ocean. These areas host unique biological communities that derive their energy from chemical reactions rather than photosynthesis.
In the case of Ceres, heat generated by radioactive decay in its core could have triggered such circulation. Liquid water, in contact with hot rocks, would have released gases and organic compounds, potentially usable by microorganisms.
This mechanism is crucial for the habitability of celestial bodies lacking external energy sources, like sunlight. It shows that life could emerge in isolated, dark environments, expanding the zones considered habitable in the Universe.
How does radioactivity influence planets?
Radioactivity is a natural process where unstable elements, like uranium or thorium, decay while emitting energy in the form of heat. This heat can warm the interiors of planets and other celestial bodies, influencing their geological evolution.
In rocky planets, this thermal energy can maintain liquid cores, generate magnetic fields, or cause volcanic activity. For small bodies like Ceres, it can be enough to melt ice and create temporary subsurface oceans.
The duration of this heat source depends on the quantity of radioactive elements present and their half-lives. On Ceres, models indicate that this heat was significant for about 1.5 billion years, offering an extended window for biological processes.
Understanding this role helps assess the past habitability of many objects in the Solar System, from asteroids to icy moons, and guides the search for life elsewhere in the Universe.