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BBC The Planets Life

where Earth is living in a neighborhood, and that influences the life here In July 1976, NASA's Viking 1 spacecraft attempted a monumental test. For hundreds of years, people had been asking the question, when planets were first discovered, "Is there's life on Mars?" It's been one of those prevalent questions throughout history. This was the first time we would look at the possibility of life, any life other than life here, on the Earth. Can you imagine what it was like at that moment when the team and myself knew that the signal was coming back, that the test had started and we were soon gonna get some kind of an answer? There is one thing that sets this planet apart from the rest. The Earth is alive. But is this the only cradle for life in an otherwise barren universe? It is perhaps the greatest question of the age. The fundamental question is: are we alone? Is life on Earth the only type of life there is? When I look out into the night sky and see all the planets and stars that there must be out there, we can't help but wonder, "Is there life there?" All we have is the example here on Earth. And even if we found just the simplest little bug on another world, and that bug was different from all the bugs we have here, that would tell us that at least in two places there's life. And from two, I think it's clear that the whole universe must be full of life. If there is life in the universe, there's still no sign of it. For decades, radio dishes have scanned the skies, listening patiently for a message beaming its way across the galaxy. So far, they have heard nothing. But with the coming of the space age, we could, at last, go out and look for alien life. In 1962, America sent Mariner 2 to Venus. Venus showed every sign of being Earth's heavenly twin. But its surface was hidden by a thick layer of cloud. What lay below was an enticing mystery. Some imagined there would be a steaming swamp, a misty haven teeming with life. Others thought that its clouds were caused by a planet-wide dust storm on a parched desert world. Mariner 2 was built to find out. It took with it the hopes of the world's first space biologist, Dr Carl Sagan. Many theories of the Venus environment have been suggested. However, new information eliminates at least some theories. Measurements with radio telescopes show that there's a region on Venus where temperatures are greater than 600 degrees Fahrenheit. It is just possible that the hot region exists at a high altitude, in the ionosphere of Venus. The surface temperature could then be almost Earth-like, and life, as we know it, could exist there. But Mariner 2 found the surface of Venus was a searing 450 degrees centigrade. Life was inconceivable here. Where else was there to look? Mercury is just a naked ball of rock, baked by the sun. Jupiter seemed a better prospect. Some biologists imagined life forms floating in its clouds like hot-air balloons. But when the first probe got there, it found the conditions were atrocious. Swirling clouds were made of super-heated ammonia. They could never support life. Emissaries to the planets were sending back depressing news. Space was a desolate place. But there was one world that still held our fascination. Humans had dreamed of going to Mars for over a century. Boris Chertok was first drawn to the Red Planet in 1924, when he saw the film "Aelita", the story of a beautiful Martian princess. As a boy, Chertok dreamt of finding life on Mars. Those dreams were thanks largely to one visionary astronomer. In 1894 a wealthy Bostonian journeyed out to Flagstaff, Arizona, and set up an observatory. Percival Lowell had heard rumors from European astronomers that Mars was crises-crossed with a series of straight lines. He'd heard them called "canals". He was so taken with the idea of a canal-building civilization on Mars that he began a systematic study of the planet, charting the features of these supposed waterways. The maps he made were the best to be had for nearly a century. When the first space mission to Mars was ready, it was 1961. Boris Chertok had grown up to be second-in-command of the Soviet space program. As it flew by Mars, the spacecraft was supposed to look for life on the surface. But before launch, Chertok decided to double-check that the life-detecting device was working properly. The truth about life on Mars remained elusive for another 15 years. And then came Viking. It was the most ambitious robotic space mission NASA had ever undertaken. It was the summer of 1976. America was on a bicentennial high, and a spacecraft was on its way to test for life on Mars. We had waited, many of us our whole career for this magic moment, when we were actually going to do the test for life on Mars. And can you imagine what it's like to be the first experimenter, the scientist who's going to be able to even ask the question, even if you don't get the answer? Once Viking was on the ground, you can just imagine the excitement. Everybody with their fingers crossed, and hoping (up) against hope that maybe we get some kind of result out of this. For seven days, Viking treated the world to picture after stunning picture of the Red Planet. They showed Mars as a frigid desert, where the temperature hovered around 100 degrees below zero. This was not the sort of place where life ought to flourish. But Viking was built to detect microscopic life lurking in Martian soil. On the eighth day, a scoop reached out to grab a sample of red earth, and the test was under way. The light went on and told us that "We're incubating, it's working now... "Any moment now you can start getting the data." Inside Viking, nutrients were added to the soil. To everyone's amazement, there was an instant response. Gas came pouring off. This gas was just what bacteria on Earth produce. Every single point was an emotional moment. "Look, look, its going you know! It's going up a little bit! It's going up a little bit more! ..." Then, when it stops... we couldn't believe it. "Hey, the curve has stopped moving!" As the team pored over the results, they could hardly believe their eyes. The sample had done just what was expected if there were organisms in it. Viking seemed to be saying there was life on Mars. We never slept. We didn't think about anything. Our lives stopped. Our children stopped. Everything stopped. Bank bills were left unpaid, while we focused on the events that were going on. Before they announced their discovery, mission scientists wanted to make sure the reaction from the soil was really caused by microbes. So Viking performed another test, one that scanned the soil for organic chemicals, the raw materials from which all life is made. All of us were so certain there was going to be organic material on Mars. And when it came back saying, "There isn't any," we said, "Well, look in another place. Somehow we picked up a sterile sample, there was something wrong." And we picked up... We moved over rocks, we dug down, we did everything we could. We did the tests again and again and again. But all came out negative. With that one result, hopes of life on Mars were dashed. There were no microbes. That initial test result was probably due to a corrosive chemical in the soil, created by intense ultra-violet radiation from the sun. Nothing could live in Martian soil. Viking was over... And it had taken all our dreams of Mars with it. Of course Viking had been sent to Mars with a particular hypothesis, to test that is... that was some kind of microbe living in the soil. And it turns out that there weren't. And so I think the sense was that Mars had come up barren, and no one was thinking about other environments on other sorts of planets. But life on Earth had its own surprise. In 1978, a scientific submarine dived to the bottom of the Pacific Ocean, and found something completely unexpected. People took vehicles like the Alvin deep submersible to hydrothermal vents on the East Pacific rise. And they found fantastic environments with tubeworms, and clams, and crabs, and all these things were surviving off the Earth's own geothermal heat. It took a while for this significance of this to sink in, but what it means is that there are other ways of supporting life, beside sunlight at the surface of the planet. And that all of a sudden opens up a whole new range of habitability that just wasn't there before. Since then, the limits of life on Earth have been pushed back further than anyone ever imagined possible. NASA scientist Chris McKay has chosen to study life in one of the world's harshest environments - California's Death Valley. Here in the salt flats of Death Valley... Not one of the places you'd expect to find life, but since Viking, we've found life in a lot of places where we wouldn't have expected. Here, underneath the salt crust here in fact, just a millimeter or so under the surface, a layer of blue-green algae. These organisms are deep enough into the salt that they can access the moisture, but they're close enough to the surface that they're getting sunlight to photosynthesize. What we found, looking at life on Earth in very harsh environments - dry, cold, hot environments - is that wherever there's water, wherever there is some mechanism trapping water, life can flourish. And that's the key. If an alien civilization called us up, "What kind of life do you have on your planet?" my answer would be, "its water-based life. What kind of life do you have?" If water was the key to life, the search for life in the solar system suddenly became the search for water. In 1979, a spacecraft called Voyager ventured out to Jupiter. It was going to study the giant world and its clutch of planet-sized moons, Ganymede, Callisto, Europa and Io. What we knew about the satellites of Jupiter before we got there at the border was very little. These things went from four points of light that were understood only marginally better than Galileo had understood them back in the 1600s when he discovered them, to entire worlds that you can map and study in detail in a space like 48 hours. It was an amazing experience. Among the moons of Jupiter, they found a jewel. Europa was smooth, covered in a layer of ice. But all over it was an intricate web of cracks. What could they be? You can make a lot of mistakes in this business by saying that "I think I know what's going on here because it looks like something else that looks familiar to me, and that's the way to go wrong many times. But it did not escape our attention that those fractures looked an awful lot like sea ice. Could there be an ocean hiding below Europa's icy skin? Beneath the cracked surface, could life exist, just as it does deep down in the Earth's oceans? We know that life is resourceful enough to use a lot of different sorts of energy. Energy sources are pretty widespread - when you talk about either sunlight at the surface of a body or geothermal energy from within. And that was what we suddenly realized. Hey, maybe we had potential to have on Europa. NASA already plans to go back to Europa to find proof of an underground ocean. Stephen Squyres hopes that one day he will design a mission to dive into it. First thing you do: yes, you would land... You would then have to get down through the ice. So you would have a probe with some kind of a heat source in it. And it would melt its way down. So then once you're in the water, it's got to, somehow, transform what it does from a melting probe to a swimming probe. And then, when you get down to the bottom, you're gonna wanna start looking for all kinds of stuff. I would want to take pictures, which means you had to take a light source... It does gonna be, if we do it, one of the most challenging... planetary missions we've ever done. Hey, it's going after one of the most important questions we've got out there. Could life have arisen on Europa? It's hard to guess until more is known about how life began on Earth. How easily did life emerge? Was it a miracle never to be repeated? To answer that, you have to travel back in time to the beginning of the Earth's history. Life must have arisen after formation of the planet, about 4.5 billion years ago. But how soon after? How quickly after? These are questions that we're trying to answer from studying the geological record of the oldest rocks. Steve Mojzsis is a geologist turned fossil hunter. To probe the earliest secrets of the planet, he travelled to Greenland, where a rare outcrop of ancient rock survives almost unscathed from when the Earth was young. In those rocks, he hoped to find microscopic traces of the most ancient life forms imaginable. During a field trip in 1995, he gathered a haul of sedimentary rocks, minerals that had formed at the bottom of the world's first ocean. The rocks that are the oldest sediments of all have been through everything that you can do to a rock, without quite melting it. "That's a good one there." They've been thrust up, regurgitated, ground up, heated, crushed... When he broke open the rocks, he found in them tiny mineral grains. He suspected they might be the charred remnants of primitive microbes. It's a preserved kind of a time capsule, this little mineral. Mojzsis put some grains into a machine called an ion probe, which deciphers the precise make-up and age of minerals. If the lumps were once living things, they would have a specific chemical fingerprint. We found that it was spot-on. A veritable stamp... of life... that's unique to it. But the real surprise was the age. The ion probe showed that the fossils were nearly 4 billion years old. As far back as we can go, 3.9 billion years ago, there is evidence of life, that life did exist here. And it existed soon after the Earth formed. And that became something of a surprise to us. It had been thought that the Earth was uninhabitable for nearly a billion years. But now it seemed that life sprouted almost as soon as the Earth itself came into being. As long as life appeared here so quickly, then perhaps it's a kind of a cosmic imperative that life should appear as a chemical consequence of the evolution of a planet. Life took hold here, not in the temperate cradle of today's Earth, but when the planet was a steaming cauldron. If life began so easily, then perhaps the Earth isn't so special after all. If life began when the Earth was to all intense an alien world. Venus will never tell its secrets. Its boiling atmosphere has turned any evidence to vapors. But the barren, cratered surface of Mars is a four-billion-year-old relic. Trying to decipher what happened in Mars's history became an obsession for some astronomers. It's interesting, all the personalities that have actually emerged in the course of Martian history on Earth... Percival Lowell built this extraordinary telescope and actually dominated the scene of his day, and had this great vision. We fault him through calling canals and so forth, but the fact is he understood the importance of water, H20, to living things. It was an important mark in history. Lowell saw his canals as traces of an ancient civilization, on a planet starved of water. In 1976, when the Viking lenders were proving that the surface of Mars was an arid desert, the orbiters were photographing the planet from pole to pole in unprecedented detail. They saw not canals, but something just as exciting. Snaking across the southern hemisphere was a network of eroded channels, flood plains and river valleys. Billions of years ago, this must have been a world of rivers and oceans. Mars, too, was a place where life could have begun. Apollo 12 proved the bacteria can survive the harsh vacuum of space. Life is tougher than anyone imagined. It is almost indestructible. Microbes had made a journey from one world to another... and survived. "Apollo 12, Houston." Could life have taken a trip like this before? The idea that meteorites might have carried life from one planet to another had existed for decades. It was considered crazy. But there were some unusual meteorites around. No one had a clue where they were from. Then two scientists proposed what seemed like another crazy idea. Twenty years ago, at a bar in Houston, a colleague and I discussed this problem, and came to a rather startling conclusion. That is, that these particular samples were rocks from the planet Mars, that had been knocked off in a large impact and had arrived on Earth.


  Life where Earth is living in a neighborhood, and that influences the life here
 
What happened billions of years ago on the other planets
What happened billions of years ago on the other planets
  Our whole attitude towards life and a planet is different now than it was back in 1976
Our whole attitude towards life and a planet is different now than it was back in 1976
  The mission is very strongly focused on rocks
The mission is very strongly focused on rocks
  Apollo 12 made man's second trip to the Moon, and changed all the ideas of life in the solar system
Apollo 12 made man's second trip to the Moon, and changed all the ideas of life in the solar system
 
We were students at the time, graduate students at Harvard, and we didn't realize, I think, the resistance that this idea would enjoy, and, in fact, that the idea was considered impossible by most of the scientific community. But, as we discussed it, the more of these we consumed, the more plausible it seemed. For several years, the idea kicked around. Then a NASA scientist took a close look at one of these mysterious rocks. So did you think this idea was crazy when you first heard it? I didn't think it was crazy, because the idea of meteorites from Mars I would say that I was a non-believer, but willing to be converted, if the right evidence came along. This is just a small piece of the original meteorite. But I guess these black areas are like which you analyzed? Yes, one like this black inclusion on top is very similar, although the one that we measured was a little larger and more spherical in shape. The greater surprise was the nature of the evidence and... When Don Bogard analyzed the grain of glass inside the rock, he found it contained gas. And to his amazement, it was an exact match for the gas sampled by the Viking lenders. This rock had to have come from Mars. I think that probably no one had anticipated that you would get direct evidence for that process in such an unlikely way as going into a small piece of glass in one of these meteorites and showing that a bit of the Martian atmosphere was actually trapped in it. We now know that pieces of Mars have been raining down on Earth for billions of years. Could life have once travelled with them? If life was present on Earth at the end of the formation of Earth, for that period the impacts would've been much more numerous than they are today. And so material would be constantly being knocked off the planets, all the planets and exchanging between the planets. So they could've carried organisms from one planet to another. The planets would not have been biologically isolated. This material going back and forth would have been, sort of, like swapping spit between the planets. In 1996, for a while some scientists thought they had found proof that life had travelled to Earth from Mars. One Martian meteorite seemed to have remnants of microbes in it that were at first thought to be Martian. That turned out not to be the case. The truth about Martian life will not come so easily.
If life did once exist on Mars, it only had a billion years to evolve, before the planet lost its atmosphere and became too cold and dry. On the Earth, there is one place that comes close to how Mars must have been when any life there would have died out - the dry valleys of Antarctica. This is how Mars must look like. The Antarctic desert is cold and dry. Mars is also a cold and dry desert, only colder and drier than Antarctica. In the high mountains, it is absolutely dry and on the surface is lifeless. But biologist Imre Friedmann thought there was one refuge for life here - the type of life he believed was the most advanced organism that could have existed on Mars. We thought that life exists more inside rocks, where micro-organisms can find their protected habitat, rather than soil, which is more exposed to the extremes of the environment. In 1976, Friedmann found some sandstone rocks with strangely mottled surfaces. And sure enough, when he broke them open, there were the signs of life he was looking for. You see under the surface a continuous green layer of photosynthetic micro-organisms. So when you look from the outside you think that the rock is dead, it is brown. But in fact, just one millimeter below the surface, the rock is green. So these rocks are not brown, these are green. The microbes cling to life, because even when it's freezing outside, water can form in droplets inside the rock. These micro-organisms have a very hard life, because most of the time they are hard frozen. And only a very few hours in a year that they are coming to life. They have the water, the temperature and the light that they can photosynthesize and really live actively. These microbes are just about the toughest form of life on this planet. They could have survived on Mars three or four billion years ago. These organisms live at the limit of existence; so to say, at the precipice. And if conditions deteriorate only a little bit, they die, and the result is extinction. Perhaps the last life on Mars left its traces locked inside rocks on the planet's surface. We're on the threshold of a new search for life on the Red Planet. This time it will be different from Viking. We've gone through a revolution in thinking. We're looking at what could be on Mars that had life, but doesn't have life any more. Is Mars a world full of fossils? NASA has committed itself to finding out. Beginning with Mars Pathfinder in 1997, it is embarked on a decade of missions to scour the planet for signs of ancient life. The rover that will go to Mars in 2003 will be equipped with a drill and a microscope to help it hunt for fossils. Stephen Squyres is designing the mission. This is totally different from Viking. The objective in Viking was to test the idea that there are today on Mars microbes living in the soil. That's not what this is about. What we are trying to do is we're trying to study what the environment was like long ago, whether or not there was life there back then, that today would be present only in fossil, you know, some kind of remnant form. The evidence is in the rocks. There are many places on Mars where fossils might be found - dry lake beds, river valleys, deep canyons. These are the places where the hunt is now on. We see places like this on Mars dried lake beds, with deposits on the surface that could contain organisms that lived in salt crust like this here billions of years ago. Imagine if you lived on Mars billions of years ago on a preserve. This would be a great place to be preserved, because in not too many years we might be going there, drilling down and pulling out those remains, and seeing what's there. Suppose we find on Mars evidence that life actually did come into being. If that's the case, Mars, literally half of the planet, I think, is covered roughly with 4, 4.5 billion-year-old rocks. In other words, there's a chance that the record of that process, the process of life coming into being from non-living material, that record is still there to be read in the Martian geologic record. So, it may be that by going to Mars we can actually understand better where we came from. The search for alien life is really a quest to understand our origins. Did life begin here on Earth? Did it travel here from Mars, or even from a more distant world? The answers could lie clear across the solar system. 20, 30 years ago, our view of life was very much bounded by the Earth.