The evidence for Mars once being habitable is steadily growing, as samples collected by Nasa’s Mars Curiosity rover have revealed a key ingredient for life in Martian rock.
Scientists found traces of nitrogen compounds known as nitrates, a vital source of nutrients for living things on Earth.
The discovery is the latest feather in the cap for the theory that while Mars is barren and dry now, it was once habitable.
The findings were published in the journal Proceedings of the National Academy of Sciences.
In their paper, the team of researchers said the nitrogen could indicate the first stage of a primitive nitrogen cycle on the surface of ancient Mars.
This could have provided a biochemically accessible source of nitrogen for life on Mars.
‘Discovery of indigenous martian nitrogen in Mars surface materials has important implications for habitability and, specifically, for the potential evolution of a nitrogen cycle at some point in martian history,’ they wrote.
The latest evidence was found by using the Sample Analysis at Mars (Sam) instrument on the Mars Science Laboratory (MSL), more commonly known as Curiosity.
The discoveries were made at areas of Mars known as John Klein and Cumberland.
The scientists note that this particular nitrate likely resulted from an asteroid impact, or lightning in a volcanic plume.
Nitrogen is a key component of things like RNA, DNA and amino acids, and thus important for life. Nitrates themselves are important because they are a good source of nitrogen for living things.
The next step will be to see if nitrates are still being produced on Mars.
‘People want to follow the carbon, but in many ways nitrogen is just as important a nutrient for life,’ said Dr Jennifer Stern, a science team member for the Mars Science Laboratory mission, reported LA Times.
‘Life runs on nitrogen as much as it runs on carbon.’
This follows news in December 2014 when the rover identified spikes of methane that scientists believe may have come from bacteria-like organisms on the surface.
‘This temporary increase in methane – sharply up and then back down – tells us there must be some relatively localised source,’ said Sushil Atreya of the University of Michigan, Ann Arbor, and Curiosity rover science team, at the time.
‘There are many possible sources, biological or non-biological, such as interaction of water and rock.’
Previous satellite observations have detected unusual plumes of methane on the planet.
But none of these previous readings are as extraordinary as the sudden ‘venting’ measured at Gale Crater, where evidence suggests water once flowed billions of years ago.
Curiosity landed in the 96 mile-wide (154km) crater in August 2012 and has been exploring the region ever since.
Since it landed, conclusive evidence has been found that Mars once had water on its surface, and now scientists are hoping to provide an answer once and for all to the greatest question: Was there, or is there still, life on Mars as well?