0:00:27 > 0:00:32Good evening. We are going to go on a journey to Mars.
0:00:32 > 0:00:37Now Mars is a world, in some ways, fairly similar to the Earth.
0:00:37 > 0:00:40And it was always been of special interest, mainly I think
0:00:40 > 0:00:44because of the chance of finding life there.
0:00:44 > 0:00:49So is there any life on Mars? We're still not sure.
0:00:49 > 0:00:51We are trying to find out.
0:00:51 > 0:00:56But meanwhile, just for a moment, cast your mind back to the 1950s.
0:00:56 > 0:01:01Science fiction enthusiasts had great fun with Mars then.
0:01:01 > 0:01:04Do you remember Quatermass?
0:01:04 > 0:01:08You know, when I was a boy, it was the great burning topic.
0:01:08 > 0:01:12Were there really canals there, and who made them?
0:01:12 > 0:01:14I remember my disappointment
0:01:14 > 0:01:18when somebody proved that Martians couldn't exist.
0:01:18 > 0:01:23It's a funny word. Worn out before anything turned up to claim it.
0:01:25 > 0:01:27Martian.
0:01:29 > 0:01:32Welcome now, Dr Chris Lintott.
0:01:32 > 0:01:35Chris, I enjoyed Quatermass immensely.
0:01:35 > 0:01:38You didn't see it in the original but you've seen it since. What do you think?
0:01:38 > 0:01:42It's fantastic, isn't it? This vision of Mars as the place
0:01:42 > 0:01:46from which aliens come, which goes right through 20th-century sci-fi.
0:01:46 > 0:01:49Even though we knew there weren't aliens on Mars,
0:01:49 > 0:01:52we'd come a long way from the 19th-century view.
0:01:52 > 0:01:56Back then observers with some quite large telescopes were drawing
0:01:56 > 0:01:58elaborate canal structures on the planet,
0:01:58 > 0:02:00believing these were the products
0:02:00 > 0:02:03of technologically advanced civilisations.
0:02:03 > 0:02:04Pure tricks of the eye.
0:02:04 > 0:02:07But of course, there are dark patches on Mars,
0:02:07 > 0:02:11once thought to be seas and then thought to be tracts
0:02:11 > 0:02:14of low-type vegetation. So what you've got to remember,
0:02:14 > 0:02:19on Mars the air is very thin indeed, what we'd normally call a vacuum,
0:02:19 > 0:02:22and it's also dry and there's no water.
0:02:22 > 0:02:24There's ice but no water.
0:02:24 > 0:02:28So the question going into the space age was whether vegetation could survive on Mars.
0:02:28 > 0:02:31And I know The Sky At Night demonstrated pretty quickly
0:02:31 > 0:02:34- what would happen if you tried to plant things there.- We did.
0:02:34 > 0:02:38We took two cacti, one we kept under earth conditions
0:02:38 > 0:02:42and the other we subjected to what we thought were Martian conditions,
0:02:42 > 0:02:44and this is what happened.
0:02:45 > 0:02:47Well, it's rather unlikely, I think,
0:02:47 > 0:02:51that any of our higher terrestrial plants would survive under Martian conditions
0:02:51 > 0:02:55although it's just possible that some very lowly forms
0:02:55 > 0:02:57which we've not yet tested may.
0:02:57 > 0:03:00But just to show you the fate of higher plants,
0:03:00 > 0:03:02I brought along tonight two cacti.
0:03:02 > 0:03:07This cactus has been quite healthily growing under earth conditions,
0:03:07 > 0:03:11and you see it's quite a nice, firm looking sort of cactus.
0:03:11 > 0:03:15This one here has spent one night under Martian conditions
0:03:15 > 0:03:17and I think you can see without any doubt
0:03:17 > 0:03:21that it's got a distinctly "morning after" appearance.
0:03:21 > 0:03:24Well, despite the lack of aliens,
0:03:24 > 0:03:28it had become very clear that Mars is a fascinating world.
0:03:28 > 0:03:31But of course, it never comes much closer than 35 million miles,
0:03:31 > 0:03:37so we are bound to be limited. The best way was to use space probes.
0:03:37 > 0:03:41The first probes went up in the early 1960s,
0:03:41 > 0:03:43both Russian and American.
0:03:43 > 0:03:50But the first real success came with America's Mariner 4 in 1965.
0:03:50 > 0:03:52Yes, and like all the early probes,
0:03:52 > 0:03:55this just give us a fleeting glimpse of Mars as it shot past.
0:03:55 > 0:03:59It's much easier to do a flyby of the planet than it is to slow down
0:03:59 > 0:04:02and go into orbit, so the early probes just shot past
0:04:02 > 0:04:04and sent back what they could.
0:04:04 > 0:04:06Mariner 4 saw some amazing things nonetheless.
0:04:06 > 0:04:10For example, it showed us the first real images of craters
0:04:10 > 0:04:13on the surface of Mars, something you couldn't see from Earth.
0:04:13 > 0:04:18And then came those marvellous pictures from Mariner 6.
0:04:18 > 0:04:21We've just had some amazing photographs sent back
0:04:21 > 0:04:23by the American probe to Mars, Mariner 6.
0:04:23 > 0:04:26Mariner 7, by the way, has been brought back under control
0:04:26 > 0:04:28and we await news from that, but meanwhile
0:04:28 > 0:04:32we have this superb series of close-ups from Mariner 6
0:04:32 > 0:04:34and I'd like to show you those pictures now,
0:04:34 > 0:04:37beginning with Mars as seen by Mariner from a distance
0:04:37 > 0:04:41of more than 700,000 miles, which of course is a great deal
0:04:41 > 0:04:43further than the moon is from the earth.
0:04:43 > 0:04:46Even so, you can see some of the dark areas which may be vegetation
0:04:46 > 0:04:49and at the bottom you can see the white polar cap,
0:04:49 > 0:04:52always thought to be due to some kind of icy or frosty deposit.
0:04:52 > 0:04:54And just look at that.
0:04:54 > 0:04:57Craters on Mars very similar to those on the moon.
0:04:57 > 0:05:00And the largest crater on that picture is about 160 miles across.
0:05:00 > 0:05:04Remember, when Mariner took that picture,
0:05:04 > 0:05:08it was only about as far from the surface of Mars as we are from Moscow.
0:05:08 > 0:05:11I wonder how those craters got there. What are they?
0:05:11 > 0:05:14Are they due to things hitting Mars or are they volcanic?
0:05:14 > 0:05:16I believe myself that most of them are likely to be volcanic
0:05:16 > 0:05:18but I remain to be proved wrong.
0:05:18 > 0:05:22Let me show you know the most spectacular of all these pictures sent back so far by Mariner 6.
0:05:22 > 0:05:26Just look at that, it's a crater 24 miles in diameter
0:05:26 > 0:05:30seen from 2000 miles. And just to give you an idea of scale,
0:05:30 > 0:05:35the area covered in that picture is about 63 miles by 48 miles,
0:05:35 > 0:05:40and I think you'll agree that that crater on Mars is very similar to a crater on the moon.
0:05:40 > 0:05:44They may not look much compared to what we have now but those images are stunning.
0:05:44 > 0:05:47It must have been wonderful to see such detail on a planet
0:05:47 > 0:05:49that's so frustrating through the telescope.
0:05:49 > 0:05:52It teases you with detail, but you never see anything like this
0:05:52 > 0:05:55and then suddenly you have Mars laid out for you.
0:05:55 > 0:05:58Yes, but don't forget, by sheer bad luck,
0:05:58 > 0:06:00the first Mariners went over Mars
0:06:00 > 0:06:03in what we now know are the least interesting parts.
0:06:03 > 0:06:05For a time, it was thought Mars might be
0:06:05 > 0:06:09rather a flat, a dull kind of world. Well, it's not.
0:06:09 > 0:06:13- Mariner 9 showed that. - But it had problems on the way in.
0:06:13 > 0:06:16Mariner 9 was supposed to go into orbit around Mars.
0:06:16 > 0:06:19It did but it found a dust storm waiting for it.
0:06:19 > 0:06:22Now, although the Martian atmosphere is so thin,
0:06:22 > 0:06:24it evidently can produce dust.
0:06:24 > 0:06:26And we've seen dust storms before.
0:06:26 > 0:06:29In fact, I for one, was prepared for this
0:06:29 > 0:06:33because for some weeks now I've been watching it from my observatory
0:06:33 > 0:06:34way down in Selsey in Sussex.
0:06:34 > 0:06:38And I've got three drawings here which will show, more or less, what I mean.
0:06:38 > 0:06:41In September, before the dust storm started,
0:06:41 > 0:06:43with my telescope I could see a great deal on Mars
0:06:43 > 0:06:46and here's one of the drawings I made then.
0:06:46 > 0:06:48This shows the southern polar cap at the top,
0:06:48 > 0:06:50it shows that rather V-shaped marking
0:06:50 > 0:06:52which we know as the Syrtis Major.
0:06:52 > 0:06:55One of those markings we always thought to be due to vegetation
0:06:55 > 0:06:57although they're not so sure now.
0:06:57 > 0:07:01Above Syrtis Major, you can see a rather featureless area
0:07:01 > 0:07:05which we call Hellas. And then, in October, the dust storm started.
0:07:05 > 0:07:08And there's a drawing that I made on October 4th
0:07:08 > 0:07:11and this time, as you can see, the polar cap is very difficult to see
0:07:11 > 0:07:14and the other features are very much less clear.
0:07:14 > 0:07:17And then the dust storm developed and this last drawing was made
0:07:17 > 0:07:22this month on November 1st, and there again in the middle, you can see the V-shaped Syrtis Major,
0:07:22 > 0:07:24but now you can only see a trace of it,
0:07:24 > 0:07:28and the entire southern part of the planet appears to be hidden
0:07:28 > 0:07:31by these swirling clouds of dust. And that is why, so far,
0:07:31 > 0:07:35we haven't had the spectacular pictures from Mariner 9
0:07:35 > 0:07:39that we'd hoped we would. Although undoubtedly they will come as soon as the dust clears.
0:07:39 > 0:07:44Global dust storms like that encountered by Mariner are relatively common on Mars,
0:07:44 > 0:07:49but they certainly puzzled The Sky At Night back in 1971.
0:07:49 > 0:07:52When you're talking about a planet like Mars where the atmosphere
0:07:52 > 0:07:56is so extremely thin, approximating what we'd normally call a vacuum,
0:07:56 > 0:07:58just how can it hold particles in suspension
0:07:58 > 0:08:01and how could those particles be whipped up?
0:08:01 > 0:08:03Arthur, I know you've got some ideas.
0:08:03 > 0:08:07I've got a little demonstration here, Patrick. This is a magnetic stirrer.
0:08:07 > 0:08:14In this little beaker on the top, I'll put some very fine silica dust.
0:08:16 > 0:08:18And if I then switch on the stirrer,
0:08:18 > 0:08:20which rotates the little bar magnet,
0:08:20 > 0:08:23I think you can see there
0:08:23 > 0:08:27that there is a considerable cloud of dust rising.
0:08:27 > 0:08:31- There certainly is.- Of course, this means that we've got here
0:08:31 > 0:08:34the thick atmosphere of the Earth.
0:08:36 > 0:08:41This doesn't apply on Mars, and what puzzles me
0:08:41 > 0:08:43is how on earth the Martian atmosphere
0:08:43 > 0:08:47manages to sustain a dust cloud. And so for this demonstration,
0:08:47 > 0:08:51I've brought along a chunk of Martian atmosphere,
0:08:51 > 0:08:56which is inside this desiccator, which has been evacuated to, er,
0:08:56 > 0:08:59- it's one hundredth, Gilbert, is it? - Less than one hundredth.
0:08:59 > 0:09:02Of atmospheric pressure.
0:09:02 > 0:09:07If I can get this magnetic stirrer to rotate again in here.
0:09:07 > 0:09:09- There it goes.- There it goes.
0:09:09 > 0:09:12We can see that there isn't any dust coming up at all from this,
0:09:12 > 0:09:16you see, because the atmosphere's not thick enough to sustain it.
0:09:16 > 0:09:18And now to try and show that we're not really cheating,
0:09:18 > 0:09:23I'll open this little cock on the top and let air in.
0:09:25 > 0:09:29- I have to do this very gently.- There we go.- Yes, you see what happens?
0:09:31 > 0:09:33Well, that seems to be an experiment
0:09:33 > 0:09:36to prove there can't be dust clouds on Mars.
0:09:36 > 0:09:39I don't understand it, Patrick.
0:09:39 > 0:09:44It may simply mean that the dust particles on Mars are very much finer
0:09:44 > 0:09:45than anything we have.
0:09:45 > 0:09:48Well, it was a good experiment
0:09:48 > 0:09:52but we now know we got the atmosphere of Mars all wrong.
0:09:52 > 0:09:55Yes, the composition's different from what you would have guessed then.
0:09:55 > 0:09:59The dust is different, too. It's much smaller and finer grained
0:09:59 > 0:10:02than you would otherwise have expected and that makes it easier
0:10:02 > 0:10:04to get up into the atmosphere.
0:10:04 > 0:10:07These days, we're used to dust storms but we also see things
0:10:07 > 0:10:09like dust devils whipping across the Martian surface.
0:10:09 > 0:10:13And the winds are quite strong there, although not very much force,
0:10:13 > 0:10:18because the air is so thin. Barometric pressure below 10 millibars everywhere.
0:10:18 > 0:10:22That's right, but still this quite evolved, dynamic weather system.
0:10:22 > 0:10:26In fact, weather on Mars has become a whole research topic on its own.
0:10:26 > 0:10:28But never mind the atmosphere.
0:10:28 > 0:10:32What Mariner 9 really showed us were the glories of the planet.
0:10:32 > 0:10:34For example, Olympus Mons.
0:10:34 > 0:10:38Olympus Mons, a volcano taller than our Mount Everest,
0:10:38 > 0:10:43much taller, and formerly seen as Nix Olympica, the Olympic snow.
0:10:43 > 0:10:45We didn't know what it was!
0:10:45 > 0:10:49But how can you not have realised it was a mountain? This thing's taller than Everest.
0:10:49 > 0:10:52- How could you not see it from Earth? - We couldn't see it clearly enough.
0:10:52 > 0:10:56It merely appeared as a patch. It might have been a lake or snow.
0:10:56 > 0:10:59We simply didn't know. It took Mariner 9 to tell us.
0:11:00 > 0:11:04And here it is. Very interesting indeed.
0:11:04 > 0:11:06You can see there the crater-like structure
0:11:06 > 0:11:08and you can see that it's got rather scalloped edges.
0:11:08 > 0:11:12And it is rather obviously a volcanic caldera.
0:11:12 > 0:11:14Here's another view of Nix Olympica.
0:11:14 > 0:11:17And you can see there a very considerable amount of detail.
0:11:17 > 0:11:21And it looks very much like a volcano of the Hawaiian type,
0:11:21 > 0:11:26only the base is about 300 miles wide, which means that it's even bigger than Hawaii.
0:11:26 > 0:11:29So Mars does seem to have been a world where vulcanism
0:11:29 > 0:11:31has played a very, very important part.
0:11:31 > 0:11:34Well, as much as you'd like to have visited Olympus Mons,
0:11:34 > 0:11:37it's a little difficult, even for The Sky At Night.
0:11:37 > 0:11:39But you did do the next best thing,
0:11:39 > 0:11:44visiting Mount Teide in the Canary Islands back in 1973.
0:11:44 > 0:11:47And I have to say, it looks pretty Martian to me.
0:11:47 > 0:11:50Now how do you think Teide matches up with a Martian caldera?
0:11:50 > 0:11:53I think very exactly. One looks, for example,
0:11:53 > 0:11:55at the beautiful pictures taken by Mariner 9,
0:11:55 > 0:11:59looking straight down on the top of Nix Olympica, for example.
0:11:59 > 0:12:02Here is a case of a caldera just like this one,
0:12:02 > 0:12:05active in the only recent past, I would imagine.
0:12:05 > 0:12:09Would you say, Ron, looking as we are now round the caldera of Teide,
0:12:09 > 0:12:11we are looking at a small version
0:12:11 > 0:12:15of the scenes that may be found when explorers finally go to Mars?
0:12:15 > 0:12:17I'm fairly sure, without the vegetation,
0:12:17 > 0:12:21without the blue sky, this is a typical solar system view.
0:12:21 > 0:12:26'Filming outside did pose a few problems for you, Patrick.'
0:12:26 > 0:12:27Sorry.
0:12:27 > 0:12:29I had hat problems.
0:12:31 > 0:12:35- The hazards of filming, I think, Patrick.- You could say that!
0:12:35 > 0:12:37Blast and hell!
0:12:38 > 0:12:42Well, Mariner 9 was a great step forward.
0:12:42 > 0:12:47What you really want to do is to land and see what Mars is very like.
0:12:47 > 0:12:50And that brings us on to the Viking programme.
0:12:50 > 0:12:52Yes, landing on Mars is a bit of a nightmare.
0:12:52 > 0:12:57It's something that's challenged space agencies throughout the history of exploration.
0:12:57 > 0:13:00The Russians had some tries. They had one success, Mars 3.
0:13:00 > 0:13:04- Not really a success.- Well, it lasted for 15 seconds on the surface,
0:13:04 > 0:13:09- so we'll give them some credit.- Yes. - But it's the challenge of getting through Mars's thick atmosphere.
0:13:09 > 0:13:11It's not thick enough, like the Earth's,
0:13:11 > 0:13:15to allow you to break on parachutes the way the Apollo astronauts did.
0:13:15 > 0:13:19But nor is it thin enough to allow you to just land with rockets
0:13:19 > 0:13:22as they do on the moon. It's a real problem, and the first to crack it,
0:13:22 > 0:13:24as you say, were the Vikings.
0:13:25 > 0:13:30But selecting a landing site for the two Viking craft proved difficult.
0:13:30 > 0:13:32They needed as flat an area as possible,
0:13:32 > 0:13:35clear of any possible hazard.
0:13:35 > 0:13:37So let's begin by seeing what would happen
0:13:37 > 0:13:40if Viking came down in a permafrost area.
0:13:40 > 0:13:45You can see it would put the spacecraft completely out of action.
0:13:45 > 0:13:50In the end, both Viking craft landed safely in July 1976.
0:13:50 > 0:13:52Touchdown, we have touchdown.
0:13:52 > 0:13:54APPLAUSE AND CHEERING
0:13:55 > 0:13:59We have, of course, landed on the surface of Mars
0:13:59 > 0:14:04and taken pictures, both immediately after landing and again since then.
0:14:04 > 0:14:07And the first pictures to come back were startling.
0:14:07 > 0:14:10This is Mars.
0:14:10 > 0:14:12Incredible pictures sent back from Viking,
0:14:12 > 0:14:15showing a red, rock-strewn landscape under a pink sky.
0:14:15 > 0:14:18The detail is absolutely amazing
0:14:18 > 0:14:22and these pictures would have seemed science fiction, not so long ago.
0:14:22 > 0:14:25Let me now show you the first picture received
0:14:25 > 0:14:27from the Martian surface itself.
0:14:27 > 0:14:29There we see the rocky landscape
0:14:29 > 0:14:32and we realise how fortunate and skilful it was
0:14:32 > 0:14:35that Viking came down safely.
0:14:35 > 0:14:37There we can see the landing pad
0:14:37 > 0:14:40and we were discussing this in our last programme,
0:14:40 > 0:14:41before Viking came down,
0:14:41 > 0:14:45when we weren't sure whether the landing would be successful.
0:14:45 > 0:14:49Well, it has been, Viking is now standing in the plain of Chryse
0:14:49 > 0:14:52and it's sending back information at this moment.
0:14:52 > 0:14:56I was impressed, when looking at this superb panoramic view,
0:14:56 > 0:14:59which I think is the most amazing picture sent back yet.
0:14:59 > 0:15:01Just look at the detail upon that.
0:15:01 > 0:15:03But now, coming into view,
0:15:03 > 0:15:08we can see things that look remarkably like sand dunes.
0:15:08 > 0:15:13I don't think they can be anything else. Would you agree, Geoff?
0:15:13 > 0:15:17Those are beautiful sand dunes with the wind coming from the left
0:15:17 > 0:15:22across the picture producing very nice streaking and sharp edges.
0:15:22 > 0:15:25Quite characteristic of sand dunes.
0:15:25 > 0:15:27Viking is now standing on the Martian surface.
0:15:27 > 0:15:30It will not come back or ever move again.
0:15:30 > 0:15:32All it can do is send back information.
0:15:32 > 0:15:34We've got to wait a long time
0:15:34 > 0:15:38until we've got a probe which can go to Mars and bring back samples.
0:15:38 > 0:15:42That lies in the next decade or possibly the decade after that.
0:15:42 > 0:15:46Well, that didn't happen. No sample-and-return probe.
0:15:46 > 0:15:51It hasn't happened even yet. But don't forget the Viking orbiters.
0:15:51 > 0:15:55They went round and round Mars, sending back priceless data,
0:15:55 > 0:15:57particularly about those polar caps.
0:15:57 > 0:16:01The orbiters are often overshadowed by the landers
0:16:01 > 0:16:03which get all the glamorous attention.
0:16:03 > 0:16:06But they looked closely at the polar caps,
0:16:06 > 0:16:09these white areas that we'd seen wax and wane
0:16:09 > 0:16:12with the Martian seasons in the telescope.
0:16:12 > 0:16:14The question was, what kind of ice is this?
0:16:14 > 0:16:19- What are the polar caps made of? - Thin layers of carbon dioxide ice?
0:16:19 > 0:16:23A thick layer of carbon dioxide ice? Well, Viking told us.
0:16:25 > 0:16:31The startling thing that's happened has been this northern polar cap,
0:16:31 > 0:16:36being composed of water vapour and not the carbon dioxide ice.
0:16:36 > 0:16:39This is staggering. When you look at the north polar cap,
0:16:39 > 0:16:42it gives the impression of being water ice,
0:16:42 > 0:16:46and we now believe that that is what it is - an ice cap.
0:16:46 > 0:16:48The water that's been found above the ice cap
0:16:48 > 0:16:51is about 20 times what we found at the equator,
0:16:51 > 0:16:54and the surface temperature is about 20-30 degrees too high
0:16:54 > 0:16:55for CO2 ice to form.
0:16:55 > 0:16:58We're quite sure that we're looking at a layer of water ice.
0:16:58 > 0:17:01The fact that the polar caps really were water ice
0:17:01 > 0:17:05made the chances of life there decidedly brighter
0:17:05 > 0:17:07and we sent something to find out.
0:17:07 > 0:17:11That's right, the Viking landers made an audacious attempt to look
0:17:11 > 0:17:15for signs of life at their landing sites.
0:17:15 > 0:17:18It was a long shot and I'm not sure what people expected to find,
0:17:18 > 0:17:21but they didn't expect the results they got.
0:17:21 > 0:17:24What they were looking for were the types of chemical reaction
0:17:24 > 0:17:27you expect if you have very simple life in the soil.
0:17:27 > 0:17:30We're not talking aliens or plants, we're talking bacteria.
0:17:30 > 0:17:34They found some unusual chemical reactions.
0:17:34 > 0:17:37But what was missing were any of the building blocks of life,
0:17:37 > 0:17:41none of the complicated molecules we'd expect, no organics.
0:17:41 > 0:17:45So we have this mysterious picture left at the end of the Viking mission
0:17:45 > 0:17:48where something unusual is happening in the Martian soil
0:17:48 > 0:17:50but who knows what it is.
0:17:50 > 0:17:55After Viking there was a surprising hiatus - probes going elsewhere,
0:17:55 > 0:17:59and I think Mars was rather pushed into the background.
0:17:59 > 0:18:05And then, in 1997, back to Mars with Pathfinder and Sojourner.
0:18:07 > 0:18:10Pathfinder came down in July 1997,
0:18:10 > 0:18:14in the region do Ares Vallis, thought to be an old flood plain,
0:18:14 > 0:18:16which indeed it is, there's various rocks.
0:18:16 > 0:18:20Pathfinder sent back pictures and the little Sojourner rover
0:18:20 > 0:18:23crawled around, inspecting and analysing the rocks.
0:18:23 > 0:18:25It sent back some amazing data.
0:18:25 > 0:18:28Sojourner went around analysing with its x-ray instrument
0:18:28 > 0:18:30the chemistry of the surrounding rocks.
0:18:30 > 0:18:34You can see in this vertical picture of the site,
0:18:34 > 0:18:37you can see a large boulder, top-right,
0:18:37 > 0:18:40with Sojourner jammed up against it, sticking out its snout,
0:18:40 > 0:18:44analysing that rock for its chemical components.
0:18:44 > 0:18:47One of the first things it showed was that on Mars,
0:18:47 > 0:18:50we not only have basaltic lavas like many on Earth,
0:18:50 > 0:18:54but rocks called andesite which are chemically different.
0:18:54 > 0:18:57This was the first new information we got.
0:18:57 > 0:19:01Pathfinder and Sojourner were the first of the new wave
0:19:01 > 0:19:03of Martian exploration.
0:19:03 > 0:19:07They were followed by Mars Global Surveyor, which went into orbit
0:19:07 > 0:19:11in September 1997 and lasted for almost a decade.
0:19:11 > 0:19:15'We have ignition and lift-off of a delta-two rocket
0:19:15 > 0:19:18'carrying NASA on an odyssey back to Mars.'
0:19:18 > 0:19:21It was quickly followed by Odyssey which detected
0:19:21 > 0:19:25the signatures of large volumes of water ice under the soil.
0:19:25 > 0:19:29Not just under the polar caps, but down towards the equator too.
0:19:29 > 0:19:32And next, Mars Express.
0:19:32 > 0:19:34This was the European mission,
0:19:34 > 0:19:38most famous in the UK as Beagle's parent mission.
0:19:38 > 0:19:41Beagle didn't make it down to the surface intact,
0:19:41 > 0:19:44or at least never told us if it did.
0:19:44 > 0:19:46But Mars Express has been a great success,
0:19:46 > 0:19:49because it discovered water again,
0:19:49 > 0:19:53it looked at the polar caps and confirmed there was water down there,
0:19:53 > 0:19:57but it also gives us the ability to see Mars in three-dimensions.
0:19:57 > 0:19:59It has a stereo camera.
0:19:59 > 0:20:03So you can produce 3-D maps of the surface
0:20:03 > 0:20:07and go flying around the surface of some of the great valleys of Mars.
0:20:07 > 0:20:12This is a stunning legacy from Mars Express which is still working well.
0:20:12 > 0:20:16To my mind, all these were eclipsed by those two splendid rovers,
0:20:16 > 0:20:21Spirit and Opportunity. Spirit was the first.
0:20:21 > 0:20:24It landed on Mars in 2004,
0:20:24 > 0:20:27in the crater Gusev which is an ancient lake.
0:20:27 > 0:20:30And we know that because of the work Spirit has done.
0:20:30 > 0:20:33These rovers were supposed to last for 90 days,
0:20:33 > 0:20:35that was the warranty, and yet they've both lasted
0:20:35 > 0:20:39more than five Earth years on the surface of the planet.
0:20:39 > 0:20:41It's an incredible achievement.
0:20:41 > 0:20:45The rovers were designed to look for clues
0:20:45 > 0:20:47to tell us what the environment was like.
0:20:47 > 0:20:51I never liked the attitude that we were going there to try
0:20:51 > 0:20:55- to find evidence of water. That's wrong.- That's not science.
0:20:55 > 0:20:57Well, Mars is what Mars is.
0:20:57 > 0:21:00Our job was to find out what Mars was like.
0:21:00 > 0:21:04If Mars has never had water at these two sites, so be it.
0:21:04 > 0:21:08Spirit landed successful, got off the lander fine,
0:21:08 > 0:21:10and everything worked but we landed on lava.
0:21:10 > 0:21:14I believe there were sediments laid down in a lake in that crater
0:21:14 > 0:21:17but a lot can happen in three or four billion years
0:21:17 > 0:21:20and we found there were lavas that were deposited on top of them.
0:21:20 > 0:21:24And that was what Spirit landed on,
0:21:24 > 0:21:28so we came looking for evidence of water and we found volcanic rocks.
0:21:28 > 0:21:32Opportunity, on the other hand, rolled to a stop
0:21:32 > 0:21:36inside a little 20-metre diameter impact crater.
0:21:36 > 0:21:40We opened our eyes and the first thing we saw, seven metres away,
0:21:40 > 0:21:45in the wall of the crater, was this outcrop of layered bedrock.
0:21:45 > 0:21:48And within weeks, we drove to it,
0:21:48 > 0:21:51found out that it was largely made of sulphate salts.
0:21:51 > 0:21:54We found ripples, evidence for water, all of that.
0:21:54 > 0:21:57It all happened in six weeks, it was remarkable.
0:21:57 > 0:22:0116-17 months later, we're sitting here and the rovers are working well.
0:22:01 > 0:22:04They're working extraordinarily well.
0:22:04 > 0:22:07The thing that we thought was going to kill them
0:22:07 > 0:22:09was dust on the solar arrays.
0:22:09 > 0:22:13Mars is a very dusty place, dust is in the atmosphere,
0:22:13 > 0:22:16it settles out of the atmosphere, it coats everything.
0:22:16 > 0:22:17The day that Spirit landed,
0:22:17 > 0:22:21the solar arrays were putting out 900 watt-hours of power.
0:22:21 > 0:22:25That's enough power to run a 100-watt light bulb for nine hours.
0:22:25 > 0:22:27As the dust built up,
0:22:27 > 0:22:32it went down and down and we got down to about 350 watt-hours.
0:22:32 > 0:22:37We think that death is about at 250. So it was getting close to the end.
0:22:37 > 0:22:42And then, one glorious day, we got hit by this gust of wind.
0:22:42 > 0:22:45It was just a blast of wind, nothing more than that.
0:22:45 > 0:22:47Cleaned off the solar arrays.
0:22:47 > 0:22:49As of two days ago,
0:22:49 > 0:22:53Spirit was producing more solar power than the day we landed.
0:22:53 > 0:22:56Because the wind cleaned it off and the sun is in a more
0:22:56 > 0:22:59- favourable part of the sky right now.- You're into Martian summer.
0:22:59 > 0:23:01Yes, that's right.
0:23:01 > 0:23:04We have so much electrical power on Spirit right now,
0:23:04 > 0:23:08we have to shut her down for about two hours every afternoon
0:23:08 > 0:23:12- to keep from overheating. - Wow.- Ha-ha-ha!
0:23:12 > 0:23:15When I next caught up with Steve, a year later,
0:23:15 > 0:23:19Opportunity had arrived at a breathtaking new site -
0:23:19 > 0:23:21Victoria crater.
0:23:21 > 0:23:26We spotted Victoria as a target the night we landed.
0:23:26 > 0:23:30There was this monstrous crater.
0:23:30 > 0:23:33800 metres in diameter, we had no idea how deep it was.
0:23:33 > 0:23:37It turns out it was 75-metres deep.
0:23:37 > 0:23:42I remember us joking that wouldn't it be cool if we had landed there!
0:23:42 > 0:23:46Never thinking that we'd have the chance to drive that far.
0:23:46 > 0:23:52But after 21 months of struggling across the dunes and the drifts,
0:23:52 > 0:23:55we finally arrived at the rim of Victoria crater
0:23:55 > 0:23:57and the place is spectacular.
0:23:57 > 0:24:02What sticks in my mind is this incredible image of Opportunity from above.
0:24:02 > 0:24:06Yes, that was very special. This marvellous camera called High-Rise
0:24:06 > 0:24:10on the Mars Reconnaissance Orbiter spacecraft,
0:24:10 > 0:24:14was turned on and operated really for the first time at Mars.
0:24:14 > 0:24:17The resolution of that camera is phenomenal,
0:24:17 > 0:24:21about 30 centimetres-per-pixel. So you could see the rover.
0:24:21 > 0:24:24- And you could see the rover tracks. - You could see the rover itself,
0:24:24 > 0:24:28you could see the high-gain antenna on the rover deck.
0:24:28 > 0:24:31It's phenomenal. And that image...
0:24:34 > 0:24:36It's hard to describe, um...
0:24:36 > 0:24:39My reaction when I saw it was just,
0:24:39 > 0:24:42it was so good to see the rover again.
0:24:43 > 0:24:45If you thought that was impressive,
0:24:45 > 0:24:48Mars Reconnaissance Orbiter had another trick up its sleeve
0:24:48 > 0:24:52as it prepared for NASA's next probe, Phoenix.
0:24:52 > 0:24:55Phoenix was going to touch down in the Martian arctic,
0:24:55 > 0:24:59but MRO managed to capture an image, not of Phoenix on the surface,
0:24:59 > 0:25:02though we got that later, but of Phoenix on the way in.
0:25:02 > 0:25:06So, this is the Phoenix probe hanging below its parachute
0:25:06 > 0:25:09as it's descending towards the surface of Mars,
0:25:09 > 0:25:12captured by MRO in orbit looking down on the scene.
0:25:12 > 0:25:17I think this photo is one of the most stunning technological achievements
0:25:17 > 0:25:20- that the Space Age has ever produced. - It must be.
0:25:20 > 0:25:24Now, Phoenix was different. It was not a rover, it was a lander.
0:25:24 > 0:25:27It came down, it stayed where it was and had various tasks.
0:25:27 > 0:25:30In particular, looking for underground ice.
0:25:34 > 0:25:38Each succeeding mission had got us closer to Martian water,
0:25:38 > 0:25:41but what we really wanted to do was sample it directly,
0:25:41 > 0:25:43and this was Phoenix's mission.
0:25:43 > 0:25:46- Touchdown signal detected! - CHEERING
0:25:46 > 0:25:49When we got to Mission Control in Arizona, it had been successful.
0:25:51 > 0:25:55We're doing well. We're meeting our goals, we're on-track
0:25:55 > 0:25:59and one of the greatest thrills was looking back under the lander
0:25:59 > 0:26:03and seeing the pressers had cleaned off the ice layer.
0:26:03 > 0:26:06We'd been told there was ice from the orbiters.
0:26:06 > 0:26:09The theory says it's going to be down five centimetres,
0:26:09 > 0:26:12and we look underneath and the thrusters had done our job for us!
0:26:12 > 0:26:16Even before you'd started digging, you knew there was ice there.
0:26:16 > 0:26:18We didn't have to dig an inch, and yet,
0:26:18 > 0:26:22we can't reach that ice cos the struts under the lander prevent
0:26:22 > 0:26:27the arm from going under there. So it's there but we can't touch it!
0:26:30 > 0:26:33Oh, that's a steep back wall, isn't it?
0:26:33 > 0:26:36And that really did dig in...
0:26:38 > 0:26:40- ..at the front there...- Uh-huh.
0:26:40 > 0:26:43When I returned to Mission Control a few months later,
0:26:43 > 0:26:48Phoenix was already feeling the chill of the harsh arctic winter.
0:26:48 > 0:26:51Temperatures have been dropping. During the summer,
0:26:51 > 0:26:55the warmest part of the day was maybe -20 degrees centigrade.
0:26:55 > 0:27:01Now it's down to -30, -35 and the nights are getting very cold.
0:27:01 > 0:27:07It could be -110, and it's heading down to -130.
0:27:07 > 0:27:13That will be the temperature throughout the entire day in the winter, -130.
0:27:13 > 0:27:17Just a few short months after that visit to Mission Control,
0:27:17 > 0:27:22Phoenix's life was over, as it was encased in the winter ice cap.
0:27:22 > 0:27:26Like its predecessors, it had given us one piece of the Martian puzzle
0:27:26 > 0:27:30and we certainly know much more now than we did in the days
0:27:30 > 0:27:33when the first spacecraft flew past the red planet.
0:27:33 > 0:27:36But the really big question remains unanswered.
0:27:36 > 0:27:40Is there life hiding somewhere on Mars?
0:27:40 > 0:27:45Well, Phoenix is still there and the other probe we sent to Mars.
0:27:45 > 0:27:51They'll stay there quite placidly. In 50 years' time, what will happen?
0:27:51 > 0:27:56Will there be bases on Mars? Will there be cricket on Mars?
0:27:57 > 0:27:59Time will tell.
0:27:59 > 0:28:03On Mars, bowlers have to contend not just with the lower gravity,
0:28:03 > 0:28:06but with the lower atmospheric pressure as well.
0:28:06 > 0:28:08It makes it hard to get a swing on the ball,
0:28:08 > 0:28:12though it is travelling much faster when it reaches the batsman.
0:28:12 > 0:28:15The down side is that if the batsman connects with it,
0:28:15 > 0:28:17it's really easy for him to hit a six!
0:28:17 > 0:28:21- COMMENTATOR:- 'A fine shot for four runs, and no mistake.'
0:28:21 > 0:28:22Good night.
0:28:31 > 0:28:34Subtitles by Red Bee Media Ltd