The search for aliens has led astronomers to scour the farthest reaches of the cosmos for signs of life.
But a new study suggests that we might not need to look so far from home.
According to NASA researchers, the icy dwarf planet Ceres may once have been home to microbial life.
Although scientists aren’t sure that living creatures ever emerged, they are now certain that Ceres had the right conditions to help that life survive.
Previous research has shown that Ceres has hidden lakes of salt water beneath the surface and organic carbon molecules – two of the necessary ingredients for life.
But the dwarf planet is still lacking anything for microbes to eat.
Now, using computer models to simulate Ceres’ past, researchers have shown that this was not always the case.
Between 2.5 and four billion years ago, radioactively warmed water would have created a ‘buffet for microbes’ that could have supported simple forms of life.
Scientists say that the dwarf planet Ceres could have once had the conditions to support abundant microbial life
Today, Ceres, which sits between the orbits of Mars and Jupiter, is a barren frozen wasteland.
In 2018, NASA’s Dawn mission found that reflective layers on the planet’s surface were actually the leftover salt from liquid that had once bubbled up through the ground.
This liquid came from vast, underground reservoirs of brine, which are now around –63°C (–81°F) – far too cold to support any known forms of life.
However, between 500 million and two billion years after Ceres formed, the decay of radioactive minerals in the rocky interior would have produced a steady supply of hot water.
According to the researchers’ simulations, water near the core would have reached temperatures exceeding 270°C (530°F).
That hot water would have surged up towards the surface, mixing with the cold water and injecting a stream of dissolved minerals and gases.
That might not sound anything like food as we would recognise it, but these sorts of hot water vents can actually be key to developing life.
Lead researcher Sam Courville, now a PhD candidate at Arizona State University, says: ‘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.
Although the dwarf planet, which orbits between Mars and Jupiter, is now a frozen wasteland, around 2.5 to four billion years ago, it may have been warm enough to support life
As radioactive materials decay, they heat water that pushes to the surface, carrying a stream of dissolved gases and minerals. Those chemicals then enter the cold reservoir of salty water and provide the fuel for life
‘So it could have big implications if we could determine whether Ceres’ ocean had an influx of hydrothermal fluid in the past’
If life had emerged on Ceres, a type of microbe known as a chemotroph that gets its energy from chemical reactions could have survived on the supply of hot water.
Professor Helen Williams, an expert on planetary formation from the University of Cambridge who was not involved in the study, told Daily Mail: ‘This research is really exciting because it shows that Ceres may once have had water at its surface.
‘Water acts as a means of transporting and concentrating elements that are also essential to life.
‘These elements are also concentrated in rocks, so water percolating through those rocks would transport and concentrate those elements near the planet’s surface, creating conditions extremely favourable for the development of life .’
Unfortunately, scientists say that our window for finding alien life on this distant dwarf planet has long since closed.
The radioactive materials that provided the heat decayed billions of years ago, removing the source of fuel.
Unlike some moons, such as Saturn’s moon Enceladus or Jupiter’s moon Europa, Ceres isn’t heated by the intense gravitational push and pull of a nearby planet, so it is now too cold for life.
Scientists had previously found that Ceres contained liquid water and organic carbon–based molecules, which are both necessary ingredients for life. Now they also know that it once had a supply of food for life to feed on
However, today Ceres is once again frozen. As this diagram shows, the oceans have frozen as the radioactive minerals decayed, leaving only a thin layer of brine that is too cold to support life
However, the researchers say that this discovery opens the possibility of finding forms of life elsewhere.
Professor Williams says: ‘These results certainly tell us that a wider class of planets could be habitable, although this depends on many other factors, such as the distance these planets are from the central star in their solar systems.’
Since Ceres was able to become habitable purely through its own inherent radioactivity, the same could be true of objects of a similar size.
In their study, published in Science Advances, Mr Courville and his co–authors write: ‘Being in large numbers, these bodies might represent the most abundant type of habitable environment in the early solar system.’
That means there could be many more planets out there with the capacity to support life than researchers had previously thought.
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