Meeting Mars

Mars is our close cosmic neighbour. At its nearest, it’s about 50 million kilometres away and sometimes as far as 400 million km. Eva Higginbotham has the Quick Fire Science on the red planet. Then we hear from University College London's Andrew Coates about the past and future Mars missions he's involved with, before speaking with the Open University's David Rothery about the red planet...

Eva - Mars is on the opposite side of earth to Venus. And is a very different place to be. Mars is named for the Roman God of war. It has two moons Phobos and Deimos the Greek personifications of fear and terror and the sons of the Greek God of war Ares. It's known as the red planet because of the thin layer of iron oxide or rust coating the surface. However, despite its belligerent namesake, in a lot of ways Mars is a calmer place than Venus. It's quite small, the second smallest planet in our solar system next to Mercury. The atmosphere on Mars is very thin, about 1% of what it is here. This might be because unlike earth, Mars doesn't have a magnetic field to keep the atmosphere. There is ice at the poles of Mars, just like at the poles of earth. And it's believed that at one point Mars had liquid water on its surface and may have had the conditions to hold life. What happened to turn it into the red planet is still not fully understood, but scientists have been sending craft to visit Mars since the 60s, trying to get a better understanding of our rusty neighbour.

Chris - Never heard it described that way before, but Mars' disposition does mean that it is a bit more welcoming to land things on compared with Venus that we were talking about just now, and as a result, there have been quite a few forays there already, and some very exciting new ventures are in the offing.

Adam - We've heard from Andrew Coates from University College London already about some of the work he's done on Venus, but what about the work he's done on Mars?

安德鲁-好吧。所以我一直幸运啊n a couple of Mars missions. So Mars Express, which went to Mars launched in 2003, and we were involved in the aspirin three instrument, which was looking at the solar wind interaction with Mars and how the atmosphere of Mars is stripped away. For me, the most exciting mission going to Mars is the ExoMars or Rosalind Franklin, as it's now, called rover. So it's named after the DNA pioneer and the clue is in that because we're looking for biomarkers, basically signs of life underneath the surface of Mars. So the really new thing that that mission is going to do is to drill up to two meters underneath the Mars surface. That's the first time that that's been done. So the reason that's important is to get below - I mean the surface of Mars is really harsh for life now. 3.8 billion years ago, we think it was very different. And we think they were the right opportunities for developing life there at about the same time life was developing on earth. But now Mars basically, you know, 3.8 billion years ago lost its magnetic field has been losing its atmosphere ever since. So it's now got a very thin atmosphere about 1% of the Earth's atmospheric pressure. So that means that the surface is basically bathed in ultraviolet. So it's a little bit like being underneath the ozone hole on earth, you know, a very deep ozone hole without the protection of a thick atmosphere. So that really is very harmful for life or anything to do with it. So you've got to get below where the ultraviolet can get to. So that's about a millimetre. Also there's oxidation has been found on the surface. So getting below that, which is about a meter below the surface. And then getting below where cosmic radiation can get to, so this is radiation from the galaxy and from the sun. These are energetic particles which can get through the thick atmosphere and provide a significant radiation environment on the surface of Mars. So you have to get below that to be able to look for signs of life. So that's why we have ExoMars, Rosalind Franklin being able to drill two metres. So the idea is to get a sample from underneath the surface from up to two meters underneath the surface, underneath all that nasty stuff. So it's a pristine sample from underneath the surface to analyse that on board the rover, and then send the results back to earth. So with all that, we hope that this mission is the most likely to actually find life signs on Mars.

克里斯-这是非常令人兴奋,不是吗?安德鲁Coates there talking about the Rosalind Franklin ExoMars Rover that is currently scheduled to launch in 2022. Now with us is Open University Planetary Geoscientist David Rothery. David, Andrew was talking about drilling down through this fairly sterile, pretty nasty crust that's been basted in radiation for billions of years. So they're not looking for life there. But he's saying get some sample from deeper, that's more likely to have the hallmarks of life or past life. So what sort of chemicals are they going for? What's an indicator of life?

大卫- Well, you look for organic molecules of various kinds and yes, if you can drill one or two metres down, you have a better chance because the surface is very oxidised and molecules break down. But there has been a static probe, not a rover, a static probe that's attempted to drill on Mars. This is Insight, which is now recording Mars-quakes. Its drill got stuck and it took a long time to get it unstuck. Drilling on a planet is tricky, which is why it's not been attempted from a rover before, but if we can do it, it's great. The NASA mission which is launching maybe end of July, maybe early August this year, their 2020 mission is going to be looking for organic molecules nearer the surface. It's not going to be drilling, but instruments called Raman spectrometers and the like are going to look at the molecules and see chemicals that were pieced together by life. Looking at chemical fossils, because if you want to look for life, you go to places where life used to exist. The next NASA rover's going through an ancient river Delta, it might be over 3 billion years old, but the sediments washed down, which may contain organic molecules. And you go to a similar environment with the Rosalind Franklin rover as well. But there you can drill a bit deeper and stand a better chance of finding molecules that haven't been broken in Mars' radiation, harsh environment, but it is, it is a tricky thing to do.

Chris - And two questions, really, if you can cover these. One is, well, how do you know that those molecules are genuinely life and they're not just produced by natural processes? And also how long do you think that that fossil fingerprint of life could last for? In other words, what's our time window? We know that we can look at various minerals on earth and we can say there are things trapped inside these crystals that would be a hallmark of life from 4 billion years ago on earth. But do we know how that works on Mars?

大卫- No, we don't to be honest, but we're hoping that these molecules can survive for 3 billion years or so. So now they won't be unchanged. It's not like some microbe died and it's sitting there not decomposing, but some of the chemicals from it last longer than others. And you're hoping to find an assemblage of chemical products, chemical fossils, which do look like they were made by life. Now you're not going to prove life was there in the past until you've got a fossil or maybe a micro fossil that you can see in a microscope on Mars. And even then people say, oh, it's just a sport of nature, it's not really a trace of life, which is why we're looking ahead to bring in bits of Mars back. And that'll be the best way to find traces of life on Mars, but it's baby steps towards the goal of demonstrating whether there was life on Mars in the past.