Sensors on Mars Rover could be tweaked to hunt for life

A PhD student at Imperial College London says he's found a way to use existing scientific tools to search for active life on Mars. Solomon Hirsch says the discovery could avoid the need for costly new missions to the Red Planet. I've been speaking with him...

Solomon - Well, the work we have here is some work we did on the equipment in our lab that closely replicates the equipment that is used on the surface of Mars. And we found that this equipment is able to distinguish between living and dead things, basically. So we've not found any evidence of life yet. But if we do, one of the first questions is, is it living now or is it dead? And hopefully the signals that we've detected in these experiments will help us answer that question in the future.

Chris - Had the people who built the analytical instruments on the rovers not realised that this was what they could do then?

Solomon - I have read previous mission statements that have said that this ability is lacking. And it comes with some limitations. The main one being that we don't know what life is going to be like beyond Earth. We're really making the massive assumption here that it's similar to Earth. It's the best assumption we have. You know, we might think things might have evolved in similar ways on other planets. So we're not saying this is 100% perfect test for all life. But with the best information we've got and using the equipment that we know that works, I think, yeah, we have discovered a new way that this equipment can be used.

Chris - What is the signal that you think you can look for then?

Solomon - We started by looking at these molecules that are found in the membranes of most cells on Earth. So if these molecules aren't there, the membrane can't form and the cell will die. And when a cell dies, these membranes break down very quickly, mainly because they're eaten by other things. So these are a really good marker of living things because they break down really quickly when something's dead. So if they're there, then we expect that something is alive. We took these compounds and put them through our system and tried to see whether there was any distinctive signal of these compounds compared to the compounds that you get after something's died. And we found a few particular compounds that could distinguish that these compounds that are indicative of living things.

Chris - What are the chemicals?

Solomon - They're called intact polar lipids, and they are long chains of carbon. One end is positively charged and the other end is negatively charged. And that kind of charge distribution causes these quite large molecules to arrange themselves into a membrane. A lot of them contain phosphate or phosphorus, not all of them. And in fact, our signal doesn't rely on the phosphorus. It just relies on the kind of most standard arrangement of these compounds.

Chris - And how do you see them? As in what instrument on the rovers and what instrument in your lab enables you to see them? And with what sort of sensitivity?

Solomon - Very good question. It's something called a GCMS, which is gas chromatography mass spectrometry. Very long winded. When I first used it, it just seemed like a magic machine. You put something in and it tells you what it is. I couldn't believe it existed. It works very well for organic chemicals, especially because life is based on organic chemicals, one of the main targets for astrobiology. The mass spectrometer part is probably the most intuitive to understand. We're trying to find the mass of the molecule basically. And then from that, we can figure out what the compound is.

Chris - And rovers like Curiosity have got these devices aboard and therefore could go looking for these compounds that you say are indicative of a life process, because if they break down so quickly, if they're there, something must be actively making them.

Solomon - Exactly. Yeah. It's been used many times before. The Viking landers had this GCMS equipment. Curiosity had it. The ExoMars, the mission that's launching in a few years time will have it as well. The Dragonfly mission, Titan will also have it. So it's well tested in space and we know it can work in those environments.

Chris - And the sensitivity?

Solomon - We know this equipment works. We know this signal should be there if something is living. And the sensitivity should be high. We need to do more work to specifically give you a number on that sensitivity. But this equipment has been used at very high sensitivities. And you can even tune the equipment. Now we know what we're looking for, you can tune it to give you a high sensitivity if you know what you're looking for.

Chris - Have you spoken to the mission teams to see if you can get this integrated into the experiments and just start sniffing around to see what's there?

Solomon - If you find some evidence of biology somewhere else in the solar system, I think, to my mind, that's just immediately. Is it living now or is it dead? So it will become useful once we kind of reach that threshold of, okay, this looks like a biological signal. Now can we tell whether it's living or dead?