THREAD: What is @NASAPersevere rover looking for on #Mars? Rocks that could prove that oxygen-producing bacteria were once common on the Red Planet. On board are samples of similar rocks from Earth that will allow the geo-lab to calibrate on Mars.... 1/n #Mars2020

I spoke yesterday to @sydneyunigeo scientist Patrice Rey in his office. He has loads of very cool rocks - similar to one he sent to colleagues in France a few years ago that ended up onboard @NASAPersevere. They range in age from 2.5 to 3.5 billion years. (yes, billions!!) 2/n

About 3 to 3.5 billion years ago a floodplain formed in what is now the Pilbara region of Western Australia. The chert rocks formed then have distinctive red in them, like this little beauty. This is oxidised iron, which shows the water had oxygen in it. 3/n

Here is another cool hematite rock that is about 3.5 billion years old THAT I HELD IN MY HAND. That's only about 1 billion years older than the formation of the planet 4.6 billion years ago 4/n

The oxidised iron in these rocks, I'm told, could only have formed if there was plentiful oxygen in both the atmosphere and water in the ancient Pilbara flood plain. This could only have occurred if cynobacteria were prevalent - an indication of early life. 5/n

So if @NASAPersevere finds rocks like the hematite chert rocks from the Pilbara that Patrice Rey is holding here in his @Sydney_Uni office, then it's a pretty sure bet that there was bacterial life on #Mars about 3.5 billion years ago. 6/n

Another sign of early life @NASAPersevere will be looking for are biomats threaded in Martian rocks. Biomats are remnants of stromatolites (no relation), which are biochemical accretion layers. You can see them in this 2.9 billion year old rock from the Pilbara THAT I HELD! 7/n

About six years ago Patrice Rey with colleagues Claire Mallard @sydneyunigeo & Nicolas Coltice @Geosciences_ENS took this cute (slightly sweary) video of them taking some of this hematite rock that eventually ended up ON FREAKEN MARS! (excuse the French - haha) 8/n

You can read this 'Postcard from Australia to Mars' about how a bit of that rock ended up on @NASAPersevere rover and is helping calibrate the onboard laboratories as they begin their search for evidence of early life on #Mars #Mars2020 . 9/n, n=9. https://www.sydney.edu.au/news-opinion/news/2021/02/17/nasa-perseverance-mars-geological-postcard-from-australia-pilbara.html