A specific area on Mars has been identified as a potential location for current life 鈥� with the organisms living far beneath the surface.
at the University of Barcelona and his colleagues investigated possible locations on Mars that could host living organisms, focusing on areas that might have the right amounts of water, heat and energy necessary for life to exist.
Taking data from the multitude of orbiters and rovers that have visited Mars, the researchers found that Acidalia Planitia 鈥� a 3000-kilometre-wide plain in the northern hemisphere of Mars 鈥� seems to have the right conditions for methanogens, methane-producing bacteria, an estimated 4.3 to 8.8 kilometres beneath the surface.
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鈥淸It is] a promising target area for future missions in the search for extant life in Mars鈥� subsurface,鈥� the researchers write.
Methanogens on Earth are found in a variety of environments including in wetlands and deep in the oceans. Some of these locations, such as extremely salty pockets of water at the sea floor, are 鈥渁nalogs of a hypothetical habitable Martian subsurface鈥�, according to Butturini and his colleagues.
The low pressure and temperature at the surface of Mars 鈥� NASA鈥檚 Perseverance rover experienced a range of about -93 to 17掳C (-136 to 62掳F) 鈥� make the possibility of life there remote. But in the subsurface, remnant water from the planet鈥檚 past, plus heat and chemical energy produced by the radioactive decay of elements such as thorium left over from the planet鈥檚 formation, could provide the ingredients for life to survive.
鈥淭here鈥檚 enough energy to, in theory, fuel life very slowly,鈥� says at Newcastle University, UK. 鈥淭he dividing times of bacteria might be hundreds of years,鈥� he says, whereas bacteria in laboratories on Earth 鈥渦nder ideal conditions can divide and grow in 20 minutes鈥�.
Using data from Mars orbiters, Butturini and his colleagues identified several regions on Mars as having an abundance of thorium that could provide this energy. Matching this with the distribution of ice picked up by missions like China鈥檚 Zhurong rover, the 鈥渕ost robust target area is the southern Acidalia Planitia at mid latitude鈥�, they write, specifically between 4.3 and 8.8 kilometres deep, where the conditions could support liquid water mixed into the Martian soil because of the predicted temperature of 0 to 10掳C (32 to 50掳F).
鈥淭he potential for subsurface sites to host an ecosystem independent of the surface is not science fiction,鈥� says Telling.
However, accessing such a deep location to see if there is actually life there would be extremely difficult. 鈥淲e can barely do that on Earth,鈥� says Telling. 鈥淚t鈥檚 going to be hard to drill down to those levels without major crewed missions.鈥�
The upcoming from the European Space Agency (ESA), due to launch in 2028, will include a drill to dig into the surface, but only down to 2 metres. Whether any methanogens several kilometres below the surface would produce evidence of life at this shallower depth is 鈥渞eally unknown鈥�, says at the University of Oxford.
So far, searches for methane in the Martian atmosphere from biological sources using ESA鈥檚 Trace Gas Orbiter spacecraft have been unsuccessful. 鈥淭he methane observations are sporadic,鈥� says Olsen. 鈥淚t鈥檚 hard to say where they鈥檙e coming from.鈥�
Yet identifying potentially habitable locations on Mars is still useful for future study, says Telling. 鈥淚f you want to look for life alive today on Mars, you鈥檝e got to look deep down,鈥� he says.
arXiv
