Katie Stack Morgan

When we first landed on the floor of Jezero Crater surrounded by these rocks, my first thought when I looked at them was, we're not in Gale Crater anymore.

Typically, you don't think of igneous rocks, which have a very fiery birth, are not necessarily the kind of rocks where you think, oh yeah, life is there.

But because these rocks had interacted with water at least over several episodes, there's a possibility that microbes might have taken advantage of the water in these rocks, the minerals and chemicals in these rocks to actually live in there too.

So it was a pretty exciting discovery to find both igneous rocks and rocks that had interacted with water.

Love the igneous rocks, but we'd been in them for about a year.

And so the first outcrop of sedimentary rocks, which it was an image called Enchanted Lake, a great name for that kind of outcrop.

I was just like, oh, these are my rocks.

And it was so great to finally be in the sedimentary rocks.

We are, I'll set the scene here, we're in an ancient Martian river valley and those sedimentary rocks are part of a fan.

So it's a deposit that was formed when water brought sediment into the crater and then the grains of sand and mud and the pebbles that that water was carrying, they all settled down onto the crater floor and left behind this sedimentary fan.

And so we were looking for evidence of sediment

Stable water, what kind of environments were there, how deep was the water, how fast was it flowing, how long, relatively, was it here?

And what we discovered was a pretty stable, long-lived and habitable lake, river and delta system.

So we were able to work out the kind of details and walk through time from a time when there were rivers flowing in to, okay, there's enough water now that we're actually forming a lake.

And then a lot of sediment comes in forming this delta that moves out over the crater floor.

And then we have at the very end, these really energetic, catastrophic floods that bring these big boulders into the crater deposited on the top of the fan.

So it was a really dynamic environment.

And it was by studying the rocks very carefully that we were able to put that story together.

And when we got there, we found very interesting features in those rocks and turned out to be amongst the most exciting rocks ever discovered on Mars.

What we found in these rocks were very distinct but small millimeter sized features.