More than any other celestial body, the planet Mars has been heavily scrutinized over the years in search of the evidence for past or even current life forms. Indeed, in March 2013, the team supervising NASA’s Curiosity rover, which is currently exploring the soil of Mars, claimed that the Red Planet had once presented environmental conditions conducive to the appearance of life. But the question remains: is there life on Mars?
To find traces of life on Mars — if there is any — we must go back billions of years into the planet’s past. Many missions to Mars have already taught us several things: fresh water in the liquid state was present, as well as oxygen in the atmosphere. Indeed, NASA’s Goddard Conceptual Image Lab released in 2013 a computer-generated video in which is shown the surface of Mars as it was 4 billion years ago. At the time, our sister planet had a thick atmosphere and large amounts of water in the liquid state formed vast oceans like on earth. Such conditions were favorable to the emergence of life. But little by little, this landscape was transformed and the blue sky gave way to ocher hues after which Mars gets its nickname of red planet.
In a study published in 2014 in the journal Astrobiology, geobiologist Nora Noffke (Old Dominion University, Virginia) had brought new elements to the record as to the possibility of a past life on Mars. In fact, by carefully browsing images taken by Curiosity in Yellowknife Bay (on the edge of an ancient lake), the scientist pointed to “striking similarities” between certain structures of Martian sedimentary rocks and others found on Earth, which are formed by microorganisms. “On one image, I saw something that seemed very familiar to me,” says the scientist, “so I took a closer look. I spent weeks investigating some of them, centimeter by centimeter, drawing sketches and comparing them with data on similar terrestrial structures. I worked on these last twenty years, so I know what to look for.”
When talking about life on Mars, some might think of advanced life form like common animals on earth. However, it is almost certain that such advanced life forms do not exist on the planet. What scientists are looking are traces of bacterial life. However, in 2017 a group of researchers have published an unfortunate study for those hoping for the discovery of bacterial life on Mars. The surface of the red planet would not only be sterile, but also highly toxic to bacteria according to the study.
But also in 2017, a study published by the Journal of Geophysical Research: Planets had pointed to the significant presence of zinc and germanium on the Red planet. However, on Earth, these two chemical elements are found together in hydrothermal deposits that also contain sulfur. This combination of elements is very suitable for primitive life forms. Hence the researchers’ hypothesis that the area where the Curiosity robot is currently evolving and where it has taken rock samples could have known a hydrothermal activity favoring the appearance of life.
The search for traces of life on Mars remains a mystery. But new missions are on the way to solve it among which NASA’s Mars 2020 mission, which is a mission to explore the planet with the help of an rover. It is being developed by NASA’s JPL center and is scheduled to launch in 2020. Apart from its scientific instrumentation, the spacecraft is a copy of the Mars Science Laboratory spacecraft that successfully landed on Mars in August 2012. One of the main objectives assigned to this new mission is the collection of samples Martian soil that should be returned to Earth by a return sample mission.