The red planet once had the right conditions to allow microbes to thrive there, the new research claims. Those microorganisms could have been able to survive for hundreds of millions of years on the ancient planet.

“We showed, based on basic physics and chemistry calculations, that the ancient Martian subsurface likely had enough dissolved hydrogen to power a global subsurface biosphere,” said Jesse Tarnas, a graduate student at Brown University and lead author of the study published in Earth and Planetary Science Letters. “Conditions in this habitable zone would have been similar to places on Earth where underground life exists.”

On Earth, organisms known as subsurface lithotrophic microbial ecosystems or SliMEs are able to live in similar conditions. They cannot get energy from sunlight, so instead peel electrons off molecules in the environments that surround them.

Around four billion years ago, Mars would have had the same conditions that sustain huge numbers of microbes down on Earth today.

The researchers are clear that the findings don't definitively mean that alien life existed on Mars. But they are important evidence that if life did get started there it would have been able to sustain itself.

By combining a range of different data about the red planet, scientists found that it probably had a habitable zone that stretched for kilometres deep and all around the world. It would have existed for hundreds of millions of years.

Scientists now hope the findings can be used to inform future trips to Mars that will attempt to find evidence of alien life.

“The mission of the 2020 rover is to look for the signs of past life,” Mustard said. “Areas where you may have remnants of this underground habitable zone — which may have been the largest habitable zone on the planet — seem like a good place to target.”

The Independent

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