Life on Mars May Have Caused its Own Extinction

As of this writing, there is no proof of life on Mars now or at any time in the planet’s history. No Martians, no spiders or girls with mousy hair (sorry David Bowie), no microbes, no tardigrades … no life on Mars. Despite that, there is plenty of hope within the science community that there could have been life on the Red Planet at one time. One potential sign that Mars could have supported some microbes is that models of its ancient atmosphere show evidence that microbes could have lived there about 3.7 billion years ago – coincidentally, when microbes were beginning to come alive in Earth’s oceans. However, while our microbes were learning how to survive and spread, these new models show that these simulated Martian creatures did something that resulted in their planet-wide extinction … and it was due to the same deadly condition we’re now encountering today on Earth – climate change. Did Martian microbes really terminate their own existence? Could the same thing happen on Earth?

"We think Mars may have been a little cooler than Earth at the time, but not nearly as cold as it is now, with average temperatures hovering most likely above the freezing point of water. While current Mars has been described as an ice cube covered in dust, we imagine early Mars as a rocky planet with a porous crust, soaked in liquid water that likely formed lakes and rivers, perhaps even seas or oceans."

In a press release from the University of Arizona, Regis Ferrière, a professor in the university’s Department of Ecology and Evolutionary Biology and a senior author of a paper on the research published in Nature Astronomy, sets the stage for building a model for what life on Mars might have looked like in the Noachian period 3.7 billion years ago when Mars was being bombarded by meteorites and asteroids on both land and in what could have been a large amount of surface water. The planet would also have had temperate climate and a thin but viable atmosphere made of carbon dioxide and hydrogen. That would be a hostile environment for Earth microbes accustomed to oxygen in the atmosphere and hydrogen in the water. However, there is one Earth microbe that lives in such a hostile place – the methanogenic microbes found around the deep submarine hydrothermal vents at the bottom of the oceans. Could early Mars have been inhabited by similar methanogenic microbes? The model says yes … but.

"Our goal was to make a model of the Martian crust with its mix of rock and salty water, let gases from the atmosphere diffuse into the ground, and see whether methanogens could live with that. And the answer is, generally speaking, yes, these microbes could have made a living in the planet's crust."

The model used spectroscopic measurements of rocks exposed on the Martian surface to predict that the water on the planet was extremely salty. The computer software then added various atmospheric compositions to predict temperatures at the surface and in the crust for each possibility. Each iteration created an ecosystem which the model would then evaluate to determine whether the methanogenic microbes would have been able to survive and, more importantly, how the microbes would have affected the environment over time. The good news is … this methanogenic life thrived at a level just a few inches below the Martian surface at the beginning. The bad news is …

"The problem is that even on early Mars, it was still very cold on the surface, so microbes would have had to go deeper into the crust to find habitable temperatures. The question is how deep does the biology need to go to find the right compromise between temperature and availability of molecules from the atmosphere they needed to grow?”

According to Boris Sauterey, a former postdoctoral fellow and study co-author, the model revealed what was causing the temperature change on the Martina surface … unfortunately and quite surprisingly, it was the methanogenic microbes themselves! The simulation shows the microbes removing hydrogen from the thin atmosphere at a very fast rate – so fast that some models showed the atmosphere being completely changed in just 10,000 years, with others stretching it to hundreds of thousands of years. By “changed,” the researchers mean cooled down … down to the point of being covered with ice – a situation that was unsuitable for microbes used to a warm hydrogen-filled atmosphere. What would you do if you were one of these gasping, shivering Martian microbes?

“The problem these microbes would have then faced is that Mars' atmosphere basically disappeared, completely thinned, so their energy source would have vanished and they would have had to find an alternate source of energy. In addition to that, the temperature would have dropped significantly, and they would have had to go much deeper into the crust."

With no warmth and no energy source, the ancient methanogenic microbes dug themselves deeper and deeper into the surface of Mars, proving that tiny microbial brains in desperate situations will – at least in computer models – make very bad decisions. While they may have been a bit warmer as they moved away from the frozen surface, they were also moving away from their only source of hydrogen energy. As these microbes dug deeper and deeper, they may have come to a grim realization – they were digging their own graves. Too late to change their tiny minds and unable to change their physiology to utilize another energy source – if there even was one – the methanogenic microbes finally succumbed to a self-inflicted extinction.

Or did they? Remember, this was only a model. The real proof will be to find fossilized microbes – but that will require drilling far deeper below the Martian surface than any Mars probes have dug so far. There is also a very remote possibility that some of these ancient methanogenic microbes survived – they could be the source of traces of methane detected in today’s Martian atmosphere by satellites or the cause of the strange 'alien burps' of methane detected by NASA's Curiosity rover. The day humans set foot on the Red Planet can’t come soon enough.

One more thing … the model shows the extinction of these Martian life forms was self-inflictied by overusing the atmosphere and creating climate change. Sound familiar? It does to Boris Sauterey, who says this may be why we haven’t found any other life in the universe yet.

"So it's possible that life appears regularly in the Universe. But the inability of life to maintain habitable conditions on the surface of the planet makes it go extinct very fast. Our experiment takes it even a step farther as it shows that even a very primitive biosphere can have a completely self-destructive effect."

Is Earth the only place in the universe where life hasn’t self-destructed? Is this a good reason to make sure we’re not on the same path as the Martian methanogenic microbes? Perhaps David Bowie was musing not about life on Mars but about life across the universe when he sang”

“It's a God-awful small affair.”