EXPERT Q&A ON MARS

with
Dr David Whitehouse,
BBC Science correspondent

Q: How did such a massive quantity of water get underground on Mars in the first place?

A: In the past, Mars was very wet and very warm. There are signs all over the surface of running water, but at the moment it is dry. So it's obviously going through a hydrological cycle - a water cycle. There must be times when there is water on the surface. Then there are times when it gets cooler, and the water disappears.

The water from the oceans may have gone into the atmosphere, and frozen out near the poles. It would then somehow have got into the spaces between the rocks and the soil. When it reached cold surfaces, would have frozen out.

This removed all the water from the atmosphere, turning it into little ice crystals near the poles. And that bears up with the calculations - until you calculate just how much water ice there is at the poles. There turns out to be far more than you can explain that way.

So we don't understand just how there is so much water ice locked up where it is. But we do think that this is the remains of Mars' oceans.

Q: So you're saying Mars used to have oceans, and was a lot warmer. When, roughly, are we talking about, and what is the evidence for this?

A: Well, when the first spacecraft arrived at Mars - the Mariners in the late 60s and early 70s - they found evidence of flowing water on the surface. They found canyons, dried up riverbeds and evidence of lakes. The water was absent, but the marks were still there.

Therefore there must have been some time, quite a way in the distance, billions of years ago, when Mars was wet, and warm and had an atmosphere. So where has the water gone? Did it escape the planet completely, or is it locked up somewhere on that planet? We now know it's still there. But how does it get there, and how does Mars go through long-term water cycles of millions of years?

Mars' polar axis wobbles in space, and therefore there are times when it was warmer than it is now. We thought that at those times, water could emerge.

Q: Is it possible that Mars formed life millions of years before it formed on Earth, and what we are now looking at is an extinct planet?

A: Certainly, astronomers think that billions of years ago, when the Earth and Mars were younger, they were very alike. They could have had very similar conditions - a lot of water - warm, with oceans and rain, with fairly similar temperatures. Certainly, it would be a puzzle if life started on one planet, but didn't start on the other.

Since then, Mars has become cold and dry, and the Earth has blossomed. So it may well be that life started on both worlds, and that life on Mars is hanging on, if you like, and that it hasn't been made extinct. But there's a complication there, if life started on Mars, or on the Earth. Was there was an exchange of rocks between the two? As asteroids hit the planets, they chuck rocks up into space - and they could land on the one another.

Is the Earth in danger from asteroids? Read the evidence.

So it may well be that if life started on one, it could have seeded the other. It's a complicated story.

Q: There's been a lot of talk about a manned expedition to Mars and colonising the planet. What are the stages and the time scale that could realise this dream?

A: Well, clearly discovering all this water ice doesn't do any harm to those who want to put men on Mars. But Mars is not like going to the Moon - Mars is 1,500 times further away. The Moon is three days travel - Mars is 300. We do not have either the technology to go to Mars, or the understanding of the planet when we get there.

So we have to look towards the American Space Agency, and say, if they wanted to put men on Mars, in 20 years' time, how would they go about doing it. They would have to do a decade of homework - and at the same time develop the technology for a manned mission to Mars. This is not a 10-year dash, like a trip to the Moon. This is a lot further, a lot more difficult, and a lot more dangerous.

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Q: Do you think it's worth spending these billions of dollars on missions to Mars, when money could be spent elsewhere? Will the scientific discoveries brought by a manned mission prove to be worth it?

A: Well, there are several answers to this. The first is, where else do you spend the money? It was thought in the 60s, that for every one dollar put into the Moon program, the American economy as a whole benefited to the tune of six dollars. So you could say that this is a good thing to do economically, because it creates jobs and wealth.

Now whether it is a good thing to do in terms of is it a good thing to go there - I would say yes, because this is one of the great adventures of mankind, and it's one of the things that our generation will be known for. We have in the next few decades, the ability to be the first on Mars.

You can look at these things and say they cost an awful lot of money. But in context of what everything else costs, they don't actually cost very much. It's probably going to be cheaper to go to Mars than stage an Olympics!

Q: So what are we talking about, a few tens of billions of pounds?

A: Well, it's difficult to say, because technology changes so quickly. What is expensive now - the development of technology and electronics and computers - could be cheaper in the future. But we're probably talking at least a hundred billion dollars.

Q: We have been pumping greenhouse gasses into our planet's atmosphere, slowly heating it up for a while now. What is the possibility of purposefully doing the same on Mars to heat it up enough to melt ice?

A: Well, if you could find a way to warm Mars - if it happened naturally, or if you could induce it - then clearly the ice would melt. Then the water and water vapour would come to the surface and enter the atmosphere, and Mars would be a different world. Mars would be very much more like the Earth.

Would you want to do that deliberately? Is it our planet to adjust and to play with? Would you want to change the conditions on Mars before we understand them? These are questions for debate.

Q: What's the gravity on Mars like?

A: Well, it's in between the Moon and the Earth. If the Earth has one gravity, the Moon has a sixth, and Mars has roughly a third. So if you were there you'd feel invigorated, because you could move a lot quicker.

Q: Is it too late to change the destination of Beagle 2, so that it will land somewhere known to have ice below the surface?

A: Well we can't do that. Although you can change the landing site of Beagle 2, it's actually landing near the equator. Beagle 2's lander has some severe constraints on the temperature and the pressure in which it can operate, so it has to land fairly low down on Mars, in a dip, near the equator, because the temperature and pressure on Mars vary quite dramatically. It would not survive where the ice is, which is near the poles.

If you want to put a lander where the ice is - which is what America tried to do in 1999 with Mars Polar Lander which unfortunately crashed, you have to design it specifically to go to the poles.

Q: Is that being planned by anybody?

A: Not at the moment. The amazing thing is that the Mars Polar Lander would have found this ice. It's a shame that the mission failed - but it may well be that with this discovery now, they revamp that mission, and fly it again.

Q: What happened to Beagle 1?

A: The reason why it's called Beagle 2 is that Beagle 1 was the ship that carried Charles Darwin around the world in the nineteenth century, and made a great voyage of discovery and found the secrets of life!

Q: Is it possible that Mars has already been contaminated with bacteria from Earth, carried by previous probes to the planet?

A: That's an interesting question. There have been several landings on the planet from America and Russia, and you have to say that some of the Russian landers in the 1970s may not have been sterilised as effectively as we could do these days. But remember that to get to Mars, you'd have to be in the vacuum of space for the best part of a year, and that may be a sterilisation process. But it's not inconceivable that bacteria could have hitched a ride.

Q: How do we know that a NASA mission would not bring back a plague of some sort from the Red Planet?

A: Well, NASA has an officer, whose job it is to protect the Earth from contamination, not only from Mars, but if you bring Moon rocks back, or samples of a comet or asteroid. You really cannot take the chance. When you do bring back the first samples in ten years time, you've got to be very careful. Not only to protect the Earth, but also to make sure you don't contaminate them.

Q: How would the discovery of microscopic life on Mars impact the way we view ourselves and the theories about how we have evolved?

A: If we find life on a second planet in our Solar System that would be amazing. Now there's the question of whether that life is independent, and that would be difficult to sort out. You'd have to look at the similarity of the two forms of life on Earth and Mars and ask could they be related in some way.

But finding life - even primitive, microscopic life - on another world, would be an amazing discovery. We've known for the past ten years that there are planets everywhere in outer space - so if there is life on planets here, that would change our outlook on how much life there is out there in space.

Q: It seems to me that finding life would be considerably less shocking than it would have 50 years ago. It seems that as we move away from a theological society, to one more scientifically based, that people would be less surprised.

You're quite right. Some people are saying that there would be something wrong if there wasn't life on Mars. But these things go in waves. The Victorians were quite happy to think of Mars as being inhabited, by intelligent beings who made canals.

As we discovered more about the planet, we found out that wasn't the case. So it's very interesting that some generations are very against life in space, and yet some can take it as natural. But this is the first generation that we can actually go and find out for sure.

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Q: So if we did find microscopic life, how long would it lead the news for?

A: It should lead the news for quite a considerable time, for it would be one of the most significant discoveries ever made about anything.