The rugged and parched expanses of Western Australia are where many of the oldest signs of ancient life on Earth have been found, embedded in the sedimentary rocks that have been undisturbed there for eons. One particularly significant finding from the Tumbiana Formation contained a substantial and telltale excess of the carbon-12 isotope compared with carbon-13.
Since carbon 12 is used by living organisms, that carbon-12 excess in the rocks was interpreted to mean that some life-form had been present long ago (about 2.7 billion years) and left behind that “signature” of its presence. What was once a microbial mat that could have produced the carbon-12 excess was ultimately found nearby.
After nine years of exploring Gale Crater on Mars, scientists with NASA’s Curiosity rover have collected a substantial number of rock samples that they have similarly drilled, pulverized, gasified and analyzed.
And as explained in an article in the Proceedings of the National Academy of Science (PNAS,) researchers have found quite a few Martian specimen that have the same carbon-12 excesses as those found in Western Australia.
Paul Mahaffy of NASA’s Goddard Space Flight Center, long-time principal investigator for the instrument that found the carbon-12 excess on Mars, called the results “tantalizingly interesting.”
And the lead author of the PNAS paper, Christopher House of Penn State University, said that “On Earth, processes that would produce the carbon signal we’re detecting on Mars are biological.” Like from Western Australia and elsewhere.
So something unusual and important has been discovered. But exactly what it is and how it came to be remains very much a work in progress.
Perhaps biology did play a role, the team writes. If so, it would involve ancient bacteria in the Martian surface that would have produced a unique carbon signature when they released methane into the atmosphere. Ultraviolet light would have then converted that gas into larger, more complex molecules that would rain down and become part of Martian rocks.… Read more