The Australian outback’s ancient geological record is again being referenced by international space agencies in their preparation for human travel to Mars.
NASA and European Space Agency astrobiologists recently travelled to the Pilbara region of Western Australia to study its stromatolites – layered rocks formed by mats of ancient microbes – to understand potential similarities with the Martian surface.
More than 3.7 billion years ago, cyanobacteria colonies in what is today called the Pilbara, began trapping rock sediments in layers.
As time progressed, the constant layering of sediment by these microbes fashioned what today appears as an array of knobbly rock formations across some of WA’s most remote areas. The process is still ongoing, with stromatolites still being formed in Shark Bay, a town about 900km southwest of the Pilbara.
Astrobiologists look for several markers to identify a stromatolite: the presence of life; its ability to leave a recognisable record of its existence; and that preservation takes place and lasts long enough to be discovered.
“That is an extremely unique and difficult process to have happen,” says Dr Lindsay Hays, NASA’s program scientist for Astrobiology, and deputy lead for its Mars sample return program.
“Only a fraction of life that ever existed [on Earth], ever becomes a fossil. It is, in fact, an incredibly lucky process to go from life living at some point to a fossil that you can find.”
The value of stromatolite study is its use as a model for, potentially, the geological structures that might be encountered by NASA’s Perseverance Rover as it makes its way across the red planet.
The rocks formed by these self-fossilising cyanobacteria are uniquely structured and are easily distinguished from non-stromatolite rocks.
But while the Pilbara is one of the world’s best examples of these structures, whether something similar has happened on Mars remains, literally, to be seen.
“Trying to do this on Earth is difficult enough,” says Perseverance Rover program scientist Dr Mitch Schulte.
“Trying to do it from 100 million miles away with rovers that have cameras, and you have to send signals that take time to go back and forth [is] even more challenging.”
The Perseverance rover is currently scouring the 1,200 km wide Jezero Crater on Mars. While water only exists on Mars in the form of polar icecaps, the crater is the remnants of ancient lakes and rivers – as cyanobacteria persist in the pools of Shark Bay today, so too may they have existed in Mars’ long-gone pools.