The Nakhla meteorite, which landed in Egypt back in 1911, has already provided the first evidence of water on the red planet, but until now signs of life have eluded astrobiologists.
They came close in 2006, when NASA scientists broke open a fragment of the meteorite and found "an abundance" of complex carbon materials inside, resembling the effects of bacteria present in Earthly rocks. At the time, however, their findings were criticised on the grounds that carbon is the fourth most abundant element in the universe.
But a recently discovered oval-shaped structure within the Nakhla meteorite has a slightly different composition to the rest of the meteorite. This was caused during the development of its structure, when the wall of the ovoid was isolated from the rest of the system through the formation of a layer of Iron oxides and hydroxides.
Scientists from Greece and the UK believe it could hold new secrets about the existence of life on Mars, and have been using X-rays and electron microscopy to prise secrets from the rock.
The main finding, published in the journal Astrobiology, is that the ovoid is made of clay - the first documented presence of extensive clay in Nakhla. This is a crucial discovery because clay is an important material for giving rise to the geological conditions necessary for life formation.
They also discovered the ovoid's sub-surface contained multiple niche environments, each slightly different from the others. If these are also present on the shallow subsurface of Mars, life could have the potential to develop, the scientists concluded.
While this is no definitive sign of life on Mars, it is an indication that it could have existed, the team said.
Professor Sherry L. Cady, who was involved in the study, said: "Though the authors couldn't prove definitively that the object of focus was evidence of life, their research strategy revealed a significant amount of information about the potential for life to inhabit the subsurface of Mars."
It's not just the potential for life originating on Mars that the study has helped scientists to understand, either; it is objects like the martian ovoid that could, ultimately, pave the way for our own relocation to Mars in the future.
“These studies may also be useful for assessing the possible habitability of the martian subsurface,” the report concludes.