The hunt for microbial Martians

with Lewis Dartnell, UCL

Mars is getting crowded: a new NASA vessel slipped into the red planet's orbit last week followed closely by India's satellite sending back its first pictures of the Martian surface. Meanwhile, a number of other countries - Russia, China, Japan - have all announced space programmes to explore the planet in future.

But why? Well, in recent years, there has been a shift from looking for microbial Martians to searching for evidence that Mars was once habitable. And, if it was, might there be fossilised evidence of organisms? Speaking with Kat Arney, Lewis Dartnell is an astrobiologist who specialises in looking for life elsewhere in the Solar System...

Kat - We're stepping away from Earth now to look at our closest planetary neighbor, and it turns out Mars is getting a bit crowded. A new NASA vessel slipped into the red planet's orbit last week followed by India's satellite, sending back its first pictures of the Martian surface while a number of other countries, Russia, China, and Japan have all announced space programs to explore the red planet, but why? Well, rather than looking for little green men actually, they're searching for evidence that Mars was once habitable and if so, whether there might be any fossilized evidence of organisms there. We're joined by Dr. Lewis Dartnell, he's an astrobiologist specializing this. Hi, Lewis!

Lewis - Hello.

Kat - What makes Mars a potential climate for life and what sort of life might we be looking at?

Lewis - Well in many ways, at least early Mars, a kind of primordial Mars, was very much like the early Earth. We think it would have been a warmer, wetter world than we find it today and with the rovers that you have just been mentioning, we found extensive evidence for kind of rivers, and babbling brooks. Curiosity touched, last year, what was last essentially river mud on the bottom of one of these babbling brooks and has looked into the kind of chemistry of the minerals we find there and realize that the water wouldn't have been too acidic, or too alkaline, or too salty, it would've been very clement, very habitable environment for life. So, what you could've done, you could've travelled in a time machine, four billion years into the Martian past, stooped down on the banks of that babbling brook and dunked in a glass, and drunk that Martian river water. It would've been the perfect environment for life to have got started in and to be sustained in.

Kat - We're talking just about bacteria here?

Lewis - Yeah. So we're not talking about little green men, perhaps little green cells, perhaps there's things like cyanobacteria which photosynthesized on Earth and would have been pumping out oxygen-rich atmosphere, maybe there's something as complex as cyanobacteria on Mars but we're not hoping for multicellular life, and certainly not kind of bug eyed aliens.

Kat - Let's certainly hope not. We've learned a lot from the curiosity rover but in terms of finding this clay, is there any chance that we can actually understand if there were bacteria in them.

Lewis - Yes, so. So far, we've been trying to characterize what the Martian environment would be like, whether it was habitable. And what we really want to do next is to see if life did get started there. If you can find so called, biosignatures or signs of life, and what I'm directly involved in at University of Lester is the next ESA, the European Space Agency mission called ExoMars and this will have life detection equipment onboard. It's got something called a Raman Spectrometer which can tell not just the kind of minerals you're looking at but if there are organic molecules, other signs of life. So this is a really exciting mission to be working on.

Kat - And when you think about life on another planet, you think about life on our own planet, it's all based on DNA and this kind of thing, and is there reason to believe that life on other planets would be based on that kind of nucleic acid?

Lewis - As Nick was saying about earlier, Carbon is just really good at doing chemistry, and so for looking for life on other planets, moons, we're gonna' be looking for organic chemistry, organic life because, simply, we know it works. "Hi. Here we are." So, it makes more sense to look for the kind of life that, a) you know works, and b) you would have a good shot at detecting chemical signs of it, but also you don't want to be too specific. You want to kind of keep quite an open mind and perhaps not look for things like DNA itself but signs of complex organic chemistry in general. So there's always that kind of dramatic tension between trying to be broad-minded, you can find stuff that's, by definition, different to you, alien but also have a good chance of finding it.

Kat - And I guess if you did find DNA, that might tell you that perhaps there is credence to this sort of DNA or organisms floating about in space and hopping off on different planets.

Lewis - Well, actually DNA isn't particularly stable in a rock over long periods of time. And we've been looking for things like amino acids and what actually might be the very best outcome for life on Mars. If you find organic molecules and find amino acids and realize that those amino acids are the same handedness as life on Earth, i.e. that they have selected the same mirror image version amino acids that would've been a very intriguing outcome. But also, might be quite frustrating because we'll find it difficult to be able to tell if you'd find Martian life. Something that had its own independent genesis on Mars, or maybe found terrestrial life that contaminated Mars, either billions of years ago inside a meteorite, or perhaps more recently with one of, you know, our own dirty probes, perhaps we're going to find your own dirty fingerprints.

Kat - Oh dear!

Lewis - The best possible outcome would be to find amino acids on Mars that have got one particular handedness i.e. it's definitely a product of life but is right-handed, not left-handed because that would tell us that it's Martian life, not Terrestrial life.

Kat - And what you've said implies that we might be looking for life that is long gone and not there anymore. Do you think there's any chance that they could be kind of living life?

Lewis - So the Martian surface today is a really unpleasant place to find yourself in and the whole planet suffered some kind of environmental catastrophe, some kind of climactic decline. So life on the surface has probably been driven extinct and the surface of Mars now is drenched in ultraviolet radiation and radiation from outer space, the cosmic rays that I study but you only have to go a couple of meters underground to get protection from that. But if we're looking for life that is like living and active today, you'd probably have to go several kilometers underground where the, you know, the warm innards of the planet's enough to thaw out that ice into liquid water which active life needs. So perhaps decades and decades down the line, we might start envisioning almost kind of an industrial action on Mars to drill very deep into the crust and find if there's an active biosphere down there.

Kat - So, future generations of scientists, when we land there, they'll be like digging down, looking for the alien civilization.

Lewis - For that, you'd probably have to have humans on Mars rather than just robots which we're sending at the moment.

Kat - But I mean though, are you optimistic that we will find life there? Where do sit on the scale?

Lewis - I kind of bet my career on it. I'm pursuing a career in astrobiology and I think there's a good enough chance to find something in my career, in my lifetime that it is worthwhile to kind of be spending time. I just find it absolutely fascinating as well. There are few areas of science which I think are so potentially profound if we get the answer we're looking for.

Kat - And do you find yourself staring up at the night sky, just looking up at it

Lewis - Wondering if anything is waving back.

Kat - Waving. Do you wave?

Lewis - No, do you wave, Kat. There's a little window into your psyche.

Kat - Just in case. Anyway, we'll be coming back to both Lewis and Nick Lane later, that's alien hunter Dr. Lewis Dartnell and his quest to find microbial Martians.