Mars, with its cold and barren landscape, may seem inhospitable to life as we know it, but it might once have been teeming with life. I mean, the Sahara desert wasn’t always a desert. Just 2,500 years ago, during the African Humid Period, it was lush green and covered in grass, trees, and lakes. Is it so hard to believe that 2,000,000 years ago the desert-like Mars might have also been teaming with life?
Astrobiologists, those involved in the study of the origin and evolution of off-world life, have in recent years attempted to answer this question with the help of technological and off-world scientific rovers that traverse and study the geological makeup of Mars. One of the key pieces of evidence supporting the idea of past life on Mars is the presence of huge craters — called bench-and-nose formations — which are thought to have once been habitable rivers. These were discovered by NASA’s Curiosity Mars rover and the scientists who analysed its data, using numerical models that simulated thousands of years of erosion.
In 2020, the continuing search for signs of past life on Mars led to the deployment of advanced robotic missions like NASA’s Perseverance rover (The image above is a photo of the surface taken by the rover. Its helicopter component can also be spotted in flight on the right of the shot). With its cutting-edge instruments, the goal of Perseverance is to explore and examine the ancient lake-bed of Jezero Crater, where scientists believe that the then-warm and wet conditions may have been conducive to life billions of years ago.
One of Perseverance’s primary objectives is to collect rock samples that may preserve traces of ancient microbial life. These samples will be stored and eventually returned to Earth, where the extraterrestrial rocks can be analysed in laboratories equipped with sophisticated instruments capable of detecting any such fossilised biomolecules.
In addition to these physical searches overground, in 2021 scientists (writing in the peer-reviewed journal Astro Biology), studied Martian meteorites and revealed that rocks below the planet’s surface could produce the same kinds of chemical energy that allow for subterranean life on Earth. Again, this was a fascinating but tentative conclusion, drawn from circumstantial evidence just like previous rover studies. So, while we can’t say definitively that there was once life on Mars, the case for it is getting much more compelling.
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