The research, published in Nature on Tuesday, used high-resolution 3D imaging data to discover evidence of ancient rivers more than 3.7 billion years ago. And co-author Dr Matt Balme, Senior Lecturer in the Planetary Environments Research Group at The Open University, said the discovery will add impetus to missions scheduled to visit the Red Planet this decade to try and work out whether living organisms ever did evolve there.
Dr Balme told Express.co.uk: “The more we look for evidence of water and clement environments in the geological record of Mars’s ancient past, the more we find it.
“I am 100 percent convinced that parts of Mars were once more than suitable for life to thrive in – whether life ever started on Mars is a different question – the BIG question that we are all trying to answer.
“This is why we spend money and time on missions like the ESA ExoMars Rosalind Franklin Rover that will launch in 2022 and is specifically designed to search for the chemical signatures of life.”
Dr Balme admitted: “That’s sitting on the fence a bit I guess – but I’m a scientist, I try not to speculate when we only have one datapoint (the Earth) to extrapolate from!”
Large rivers once flowed on Mars, said Dr Balme
Nevertheless, while he believes conditions were once right, he is less convinced Mars harbours living organisms today.
He said: “So while I can’t give a percentage for ‘did life ever exist on Earth’, I can say that I don’t think that life exists on Mars now, or else we would have detected its products in the atmosphere.”
However, he did leave the door open slightly, saying: “The only fall back is that it could exist so deep underground that it is almost totally insulated from the present-day atmosphere.”
As for the Martian environment in what was is known as the Hesperian Era, he added: “These would have been substantial rivers, maybe tens of metres across, set within loose materials forming flat-lying floodplains at the bottoms of broad, shallow valleys.
“They could have looked like rivers you’d find in some of the most arid places on Earth today, such as the streams that form in the Dry Valleys of Antarctica.
“So if you can imagine a river on Earth without grass, trees or bushes, in a barren landscape that was probably still really rather cold and dry, then you’d be close to imagining what standing on martian river bank, 3.7 billion years ago might be like.”
Dr Balme’s study suggests the rivers flowed for at least 100,000 years – although it is difficult to be precise – and it could have been much longer.
He explained: “The problem with trying to work out “time” from the layers seen in a cliff-face like this is that there are periods of ‘lost time’.
“We can clearly see that there are some parts of this outcrop that contain stack of shallow u-shaped layers, indicating that the river was active and depositing sands and migrating around the local area, and we can estimate how long these took to form by comparison with similar sized deposits on earth – and this is where we get our estimate of at least 100,00 years from.
“But there are also stark tops and bottoms to these sets of u-shaped layering. This shows that the river sediments here were eroded away, creating a ‘planed-off’ surface.
“Perhaps the river dried out for a time, or the path of the river shifted to another region, leaving this part abandoned.
“The point here is that we don’t know how much ‘lost time’ occurs in these periods of inactivity. It could be a few tens of years, or tens of millions!
“So yes, the river system that we see a part of here could have been active for much longer than 100,000 years, with the river shifting around the landscape to areas where we cannot now see it.
“Or, there could have been long periods where the whole river system was inactive.
“Why did the river become inactive? Probably because Mars environment shifted to being slowly drier and colder, and the atmosphere less able to keep the surface warm.”
Addressing the question of where in the solar system – and the universe – to look for life, Dr Balme said: “Mars is probably as good a place to look for extra-terrestrial life as any, and has many advantages: we know that in its past it was more Earth-like in terms of rock, minerals and liquid water being available (all good for life!), its relatively easy to explore (compared to drilling into the ice crust of an outer planet satellite), and we can realistically expect to collect samples from Mars and return them to Earth for study within realistic time and budget constraints.
“This is important because the parts of Mars where we are most likely to find evidence of past life are similar in age to the time periods when life started on Earth, so if we do find evidence we can make a direct comparison with Earth.
“Having said that, if we can find an ExoPlanet with a perfect Earth-like environment and evidence for certain gases in the atmosphere, then that might also be a great focus, or if the SETI programme turns up something amazing then we can’t ignore that!”
And if life is discovered in the cosmic neighbourhood, it would have massive implications, said Dr Balme.
He added: “If we find solid evidence for extra-terrestrial life anywhere within the solar system, or even in any of the nearer stars, this would suggest life is common in the Universe.
“It would be massively improbable that the only two examples of life in the galaxy were right next to each other!”