Scientists Share Their Thoughts on the Appearance of Ancient Martians

According to NASA Administrator Sean Duffy, the US space agency now believes that these traces could have been left by ancient life forms that lived billions of years ago. Now scientists have figured out what these alien organisms could have looked like, writes the Daily Mail. Any life that arose on Mars would have to contend with harsh radiation, weak gravity and temperatures that can fluctuate between 20°C (70°F) during the day and -153°C (-225°F) at night. However, the scientists behind this groundbreaking study argue that the evolution of some life forms is still possible. If there was life on Mars, it would almost certainly consist of very simple microorganisms, such as bacteria.

In the unlikely event that more complex life did arise somewhere on the Red Planet, it would need to develop special adaptations to survive in this incredibly harsh climate.

While exploring a region known as Bright Angel, NASA's Perseverance rover spotted a group of unusual markings that resembled the spots of a leopard. Scientists call these spots "reaction fronts," and they are contact points where chemical and physical reactions have occurred in the past.

Importantly, the Daily Mail points out, Perseverance's onboard laboratory found that these spots contain two iron-rich minerals: vivianite, which is found in decaying organic matter, and greigite, which is produced by microbes on Earth.

Dr Keiron Hickman-Lewis, an Earth scientist at Birkbeck, University of London and co-author of the NASA report, told the Daily Mail: "The kinds of organomineral assemblages seen at Bright Angel and reported in this paper are known to be generated by microbial life on Earth, so it's a very exciting observation to see something so similar on Mars. Certainly, I think this is the strongest potential evidence for life on Mars found to date."

Scientists cannot yet rule out that the spots may be caused by non-biological processes, and Dr Hickman-Lewis says it is not "smoking gun".

However, after spending a year examining the evidence and looking for alternative explanations, the researchers are now confident enough to say that it could be a "biosignature," an elusive sign that proves the existence of life.

Potential signs of life have been discovered in an area called Jezero Crater, an impact basin north of the equator, the Daily Mail reports. Although it is now a barren wasteland, billions of years ago Jezero Crater was filled with water that could have been home to life. If life did exist in these waters, the most likely explanation is that it was some kind of simple microorganism.

Dr Hickman-Lewis said: "The environment in which these potential biosignatures were found appears to be rich in water at low temperatures and therefore very favourable for microbial life."

In their paper published in the journal Nature, the researchers suggest that microbes could have fed on the natural carbon, sulfur and phosphorus found in the rocks. These microbes then excreted the minerals that we now see as leopard spots. Conditions on the surface would have been incredibly harsh, but the researchers say life could still have eked out a mere existence.

Dr Sanjeev Gupta, an Earth scientist at Imperial College London and a member of the research team, told the Daily Mail: "Billions of years ago, there was liquid water on the surface of the planet, so it was a habitable environment. Simple microbial life could have existed here. There's a lot more we can say."

Since we can only see possible traces left by these microorganisms, it is difficult to say what they might have looked like or behaved like. However, some very general predictions can be made based on parallels with Earth, notes the Daily Mail.

Professor Michael Garrett, an astronomer at the University of Manchester and director of the Jodrell Bank Centre for Astrophysics, who was not involved in the study, told the Daily Mail: "Think about hardy bacteria, similar to terrestrial extremophiles, that thrive in very salty, cold or low-oxygen conditions here on Earth. Good analogues are microbial communities in very salty lakes, or microbes living several kilometres beneath the Earth's crust, or in the high desert of Chile. These examples show us that life can be harsh, minimalist and resilient, even in places with harsh conditions on the surface."

If these leopard spots are indeed biosignatures, the researchers say it is unlikely that they existed in only one place. Perseverance is currently studying very ancient rocks outside Jezero Crater for signs of more widespread life.

However, it is highly unlikely that more complex life arose anywhere on the Red Planet. Researchers believe that microbes appeared on Mars around the same time as life on Earth. However, after about a billion years, Mars' climate began to change rapidly as solar winds stripped away its atmosphere, leaving the planet very cold and dry.

Professor Garrett said: "These harsh conditions on Mars after 1 billion years will place severe limits on the body size and complexity of any life form. It took another 3 billion years for truly complex life, such as animals, to evolve on Earth, where conditions were much better for supporting complex, energy-hungry life forms."

In the unlikely event that more complex life did arise, Mars' harsh conditions would also place severe constraints on what it might look like.

"It would have to be adapted to the intense ultraviolet radiation from the Sun, extreme cold and limited liquid water - we don't really see complex animal life in those conditions," says Professor Garrett. "If they were there, they would need protection from the sun's ultraviolet radiation - thick skin, for example, or perhaps living mostly under the Martian soil."

This means that the complex life form could resemble terrestrial creatures that live in extremely harsh conditions, such as desert-dwelling lizards.