Washington - NASA announced on Thursday that its robot explorer Curiosity, which landed on Mars in 2012 and has been exploring there ever since, found organic molecules in rocks formed three billion years ago, a discovery that could indicate that there was life on the Red Planet at that time.
Paul Mahaffy, Director of NASA's Solar System exploration division, said that although this is an exciting discovery scientists still cannot confirm how the molecules originated.
They could be evidence for the development of ancient life on Mars but they could also have come from a meteorite or other sources, Efe reported.
Despite the fact that it is still not clear how these molecules were created, NASA emphasized that these kinds of particles could have been the food source for hypothetical microbial life on Mars.
Jennifer Eigenbrode, with the NASA's Goddard Space Center in Maryland, said that the organic molecules found on Mars do not provide specific evidence of life since "they could have come from things that are non-biological".
In any case, however, the molecules may provide key information to scientists in their continuing search for life on Mars, since "All life that we know of is based on organic molecules," Eigenbrode explained.
She said that although the surface of Mars is presently "inhospitable", indications are that in the distant past the Martian climate allowed liquid water to exist on the planet's surface.
The data gathered by Curiosity reveal that billions of years ago there was a shallow lake of water inside the Gale Crater on Mars that contained all the ingredients necessary for life as we know it, including chemical building blocks and energy sources.
Eigenbrode said that -- now that potential signs of ancient life have been found -- future missions to Mars will delve deeper into the issue of organic molecules and other possible markers for life.
Curiosity found the first indications of water on Mars in 2013 and it also determined that the concentration of methane in the planet's thin atmosphere fluctuates regularly with the Martian seasons.
Although the origin of the gas is unknown, scientists say it could have been trapped underground as a byproduct of organic processes in the distant past and is now slowly seeping out.