Mars 'very likely' hosted alien life in the past, study suggests

According to a recent study, "methanogens"—a class of organisms—likely lived in underground lairs on Mars billions of years ago and may still do so today.

The study offers a tantalising glimpse of how microbial aliens could have emerged and survived on the red planet and concludes that Mars was "very likely" habitable to life more than 3.7 billion years ago and may still be home to hardy organisms today.

Mars, today, is cold and dry. But there is a wealth of evidence to suggest that this world was once warmer, wetter, and more hospitable to life. In order to look for signs of extinct aliens that may have lived there billions of years ago, NASA's Perseverance rover is currently exploring the dried-out remnants of what was once a vast ancient lakebed on Mars, known as Jezero Crater.

A team of researchers led by Boris Sauterey, a biologist at the Institut de Biologie de l'École Normale Supérieure in France, has published a groundbreaking study that evaluates the possibility of hydrogen-eating methanogens on early Mars and makes predictions about the future survival of any hypothetical descendants of these organisms.

Even though there is no proof that life has ever existed on Mars, scientists have theorised that methanogens, which are among the oldest life forms on Earth, may have thrived in the planet's early environments. Methanogens produce methane as a waste product and get their energy from carbon dioxide and hydrogen, both of which were present on ancient Mars.

The researchers also found that the early Martian microbes' activities would have caused a global cooling effect, possibly resulting in their own extinction. For billions of years, life has also changed the climate here on Earth, but these feedback loops have generally preserved and even improved the habitability of our planet. According to the new study, transient life may develop on many planets, but the kind of long-term habitability we have on Earth might be an exception.