Perseverance report published

What Perseverance has revealed about the potential for life on Mars...
25 November 2022

Interview with 

David Rothery, Open University




To Mars, and a treasure trove of information from the Mars rover Perseverance which has just been published. Perseverance landed spectacularly in Mars’ Jezero crater in February of 2021, with the mission of surveying the nearby area for signs of life - or at least signs that life may have once been supported. Images from space showed that the Jezero crater contained what used to be a river delta; so where better to start the hunt for extraterrestrials than a place that was once probably full of water. The rover has been gathering data ever since and, this week, a collection of papers were published documenting the initial findings. Planetary geologist David Rothery from the Open University took Will Tingle through what’s been discovered so far…

David - But there's history of igneous activity there on the floor of the crater. Now a delta flowed across that crater floor and leaves us the delta we see very prominently from the spacecraft images looking down on Jezero crater. But that's not the original delta, that's just an erosional remnant. Most of the delta rocks have been eroded away. And where have they gone? It's a very good question. Some rocks have been flushed out of there as an outflow channel going out of the crater, but maybe a lot's been removed by the wind. The curious thing is, you see the front of this delta, there are some damn big boulders there brought in by torrential floods: metre size boulders potentially. And you can't blow those away in the wind, especially in Mars' very tenuous atmosphere. So there are processes going on that we don't really understand. But what's published this week is the lavas on the floor of the crater were altered by water.

David - So it's clear there was a body of water overlying these lavas and there's been a certain amount of alteration of the original rocks formed by cooling from molten lava being carbon deposited. And then later on some salts precipitated from brine, so water got really salty. So we've got an alteration history, but we haven't yet got samples of the lake bed rocks that might have microbes in them - or not as published. The rover is now at the very bottom of the steep face of a delta in amongst some very fine grain sediments. And that's a chance for finding some fossilised microbes. And I guess there will be caching some specimens for later return to earth from that very site where they are now.

Will - It's good that you mentioned that because it did say that on one of the papers that Perseverance will be collecting up to 38 samples of rock and regular earth (regular being dust that's on top of bedrock.) They plan to be brought back and returned for analysis in earth laboratories. I wonder if you could shed any light on how they plan on bringing these samples back.

David - One plan, given that the Ingenuity helicopter has functioned so well, is to use helicopters to go and collect these little bits of samples and bring them back to a central point from where a future mission can return them. But they're probably going to be using the Perseverance rover as well to bring samples to our collection points. But Perseverance has a big job to do. First, it's going to climb up the front of its delta. It's about a hundred metres high to get it from the bottom of the delta to the top. The top continues to slope upwards. It's got quite a traverse to go through to see the whole sequence of delta morphologies. So we're a long way off yet bringing samples back to work. But it's collecting samples in collection tubes ready to be retrieved when we've figured out quite how we're going to do it.

Will - How optimistic are you that we may find remnants of life, be it alive or in a deep torpor or even just fossilised remnants.

David - There are organic molecules that have been found. That doesn't mean life. Organic is just carbon and hydrogen bonded together with oxygen and so on. So there are some quite complex molecules in amongst the rocks. But we won't find microbes with this mission - unlikely to anyway. But future missions may have a better chance. Mars in the past surely had life. Even if it didn't develop its own life, it could have had life carried from earth. If there was a big impact on earth and a rock gets flung out from earth, it will have some bugs in it. Some of those bugs will survive passage to Mars and can seed Mars. Either life on Earth came from Mars or life on Mars came from Earth. So I'm sure Mars had things living on it in the deep past at the same time Earth had early microbes present, but they're going to be hard to find.


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