The Australian Outback and the Search for Life on Mars

In June of 2023, members of NASA's Mars Exploration Program, the Australian Space Agency, ESA (European Space Agency), and the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO), joined together on an expedition to visit three incredible field locations containing stromatolites, fossils of ancient microbial life, and the oldest, most convincing evidence for life on Earth. Stromatolites are rock features that are usually dome or cone-shaped, and are caused by photosynthetic lifeforms precipitating minerals throughout their life cycle, while continuously climbing upwards towards their energy source of the sun. Over time these microbial communities begin to form layers of rock that rise up to form strange shapes in the geological record that cannot be formed in any other way. Could these structures be found on other planets? On Mars? As we search the solar system and beyond for biosignatures, or signs of life, it's crucial that we know as much as possible about the nature of life on Earth. Knowing how quickly life took hold on our planet, and how that life evolved over time, will help NASA scientists understand the possibilities for life on other worlds and how best to search for them. Mars and Earth may have had very similar pasts, and the surface of Mars shares many qualities with the stromatolite outcrops in Western Australia. If life could take a foothold on Earth 3.5 billion years ago, could it also have taken a hold on Mars?

What is said in the film

All right. Well, welcome, everybody, to the Pilbara. We're delighted to be able to take you into a site containing the oldest and most convincing evidence for life on Earth in rocks that are 3. 5 billion years old. It's a great opportunity to come and see what you might be looking for on Mars.

We can see rippled sediment, beautiful ripples here continuing along and it comes up to the edge and it pinches out against the side of the stromatolite and then continues over here on the other side. Beautiful ripples through here... So, what we’re looking at here in Western Australia are what are known as stromatolites. These are rock features that were precipitated or caused to precipitate by mats of microorganisms that were living at the time, again, 3. 5 billion years ago.

So a stromatolite is a physical feature. Usually it's either a dome or a cone-shaped feature, and these are formed when single-celled organisms living together in a colony either trap and bind sediment or precipitate sediment on them. And then these photosynthetic organisms grow up. And so you see these layers that repeat in that shape. Sometimes they branch, sometimes they grow, sometimes they shrink.

But what it is, is evidence of a colony of life from the earliest evolution of life, the earliest fossils that we have. And these organisms then had their presence here on Earth captured and preserved in the rock record for all of this time. And so what we're looking for are these particular structures that these microorganisms made that are distinct from what geology normally does. So the greatest thing about Australia is that it has some of the oldest rocks and some of the best preserved rocks for all different time periods in Earth's history. and it's important for us to come here because what we're looking for here is the oldest convincing evidence of life on earth.

And in our search for evidence of life on other planets beyond Earth, especially Mars, it's important to understand how difficult it is to convince people of what we're seeing here on Earth as being evidence of life from 3. 5 billion years ago. That is an extremely unique and difficult process to have happen. So there's only a fraction of life that ever existed, ever becomes a fossil. It's in fact an incredibly lucky process to go from life living at some point to a fossil that you can find.

Earth and Mars may have had similar pasts. And the more we learn about Earth's past, the more we may be able to apply it to Mars. Now that we're collecting samples at Mars, wouldn't it be unbelievable if we were able to find something that indicated similar things that we're finding here on Earth that indicate, hey, there may have been life in the in the distant past on Mars?

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