Life on Mars was possible, scientists say

Telegraph

17-04-2025

Mars was once habitable, scientists have said, after discovering evidence that a carbon cycle once operated on the Red Planet.
Finding life on Mars is a holy grail for researchers, but it is still not clear whether the planet could have sustained life.
Although the Martian landscape shows clear signs that liquid water once flowed on the surface, it would have required a lot of carbon dioxide in the atmosphere to keep it warm enough.
Previous rock sampling suggested there was not enough carbon on the planet to create such an atmosphere, leaving experts in a quandary about whether Mars really was a wet, warm planet that could allow life to evolve.
Now, new sampling by Nasa's Curiosity rover has found large deposits of siderite, a carbon-rich mineral, in the Gale Crater, a dried-up ancient sea.
It suggests that the atmosphere contained enough carbon dioxide to support liquid water, and as the atmosphere thinned, the carbon dioxide was absorbed into the rocks.
'It tells us that the planet was habitable and that the models for habitability are correct,' said Dr Ben Tutolo, an associate professor at the University of Calgary, and a scientist on the rover team.
'The broader implications are that the planet was habitable up until this time, but then, as the CO2 that had been warming the planet started to precipitate as siderite, it likely impacted Mars's ability to stay warm.
'The question looking forward is how much of this CO2 from the atmosphere was actually sequestered? Was that potentially a reason we began to lose habitability?'
'Potentially habitable environments'
It is thought Mars lost its atmosphere around four billion years ago, about the time that life was starting to get going on Earth.
Carbon is the chemical backbone of life on Earth, being the fundamental building block of life and regulating the planet's temperature.
But to do this, it needs to be constantly moving around the planet, a process which happens through mechanisms including photosynthesis, respiration, erosion and volcanic activity.
Nasa had hoped that sedimentary layers at the Gale Crater would show evidence of carbon being pulled into the rocks because they were formed when Mars was drying out and becoming colder.
The findings suggest that large amounts of carbon dioxide have been locked into the planet's crust, and if they are representative of similar regions globally, then it suggests a huge carbon reservoir, indicative of a thick atmosphere.
Dr Tutolo says it's clear that small changes in atmospheric CO2 can lead to huge changes in the ability of the planet to harbour life.
'The most remarkable thing about Earth is that it's habitable and it has been for at least four billion years,' he adds. 'Something happened to Mars that didn't happen to Earth.'