Alice & Andy in the Universe of Wonders: The Planet Earth [US Version]

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In Cox married U. Their first son, named George, was born on 26 May Milinovich also has a son, named Moki, from a previous relationship. The family currently lives in Battersea. Archived from the original on 25 September Retrieved 9 March From Wikipedia, the free encyclopedia. This is the latest accepted revision , reviewed on 18 September For other uses, see Brian Cox disambiguation. Richard Feynman Carl Sagan.

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The London Gazette Supplement. Wonders of the Solar System. Wonders of the Universe. Retrieved 12 November Professor Brian Cox delivers a key note speech". We're always following some exciting Jupiters. We don't tell anybody about them, but at any given time we have a half a dozen Jupiters that look like our own Jupiter. If their hunches are confirmed, then not only are there other solar systems that look like ours, there may be lots of them.

Ninety percent of the stars show no close-in Jupiters. Those are stars that could easily have an Earth in an Earth-like orbit. I think of the stars we're following, I would bet at least half of them have rocky Earth-sized planets going around them. Just a decade ago astronomers could not be sure if there were any planets beyond our solar system. Today, we have a much better picture of our galaxy. And Geoff Marcy estimates that of the several hundred billion stars in the Milky Way, about five percent have small, rocky planets that might harbor life.

If he's right, that could mean 10 billion Earthlike planets.

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But before you start packing your bags to visit an extraterrestrial neighbor, consider this: It's a crucial factor in the Drake Equation: On a planet where no life exists, like our own early Earth, how does life suddenly come into being? Is the spark of life rare or common? Twenty-five years ago, most people, when they thought about the origin of life, thought in terms of inherently improbable reactions that would actually occur because of the fullness of time. Andy Knoll is a paleontologist who studies fossils for clues to how early life evolved on Earth.

Before about million years ago, all life on earth was tiny, single-celled creatures, so small that Knoll and his colleagues do most of their work with microscopes or in chemistry labs. The big surprise is that no matter where they look for signs of ancient life, they find it. Our planet is about four and a half billion years old. We have evidence from the oldest rocks that we know of, at least the oldest sedimentary rocks we know of, that by about 3. Scientists haven't figured out exactly how that first spark of life happened, but since it seems to have sparked early on, then maybe it isn't so hard.

Most people think that whether or not we understand what the chemistry that leads to life is, that it's a chemistry that under the right conditions will pretty much go and It might unfold in thousands of years or a million years. A lot of people think if you can't do it in a million years, you probably can't do it at all. So, what is required to get it all started? Here on Earth, the chemistry of life relies heavily on the element carbon.

Carbon is one of the most versatile elements, each carbon atom can hook up with one, two, or three or four other atoms. It can even link up with other carbon atoms creating long chains or rings. Throw in a few other elements, and you've got amino acids, the ingredients of proteins, the building blocks of life as we know it.

Carbon is a very useful element to sit at the center of life's chemistry. There's a lot of it in the universe. It's made very easily in stars. It makes very complicated, meshed-together compounds which have the possibility of changing each other's properties. You can have a really complicated, complex setup with carbon. I'd expect that very nearly all life forms we come across that are matter-based are going to be carbon-based. If carbon helps make life happen, then there might be a lot of life out there.

Carbon is one of the most common elements in the universe. So if it's got carbon, what else does life need? Lots of oxygen in the air? We tend to think life belongs in a place that's, well, comfortable for us. But is that really true? In the last few years, we've been finding life practically everywhere on Earth, and not just the obvious spots. Microbes are thriving under rocks in the driest, hottest deserts. Life's doing just fine in the dark bottom of the oceans, warmed by deep sea vents.

And now, life is turning up in some of the coldest, bleakest conditions imaginable, including the ice sheets of Antarctica and Greenland. So now that we've found life not just surviving, but thriving just about everywhere on Earth, suddenly it's looking more likely that life might thrive in lots of places beyond Earth, even if we would find them a bit uncomfortable. If life is common, then we should be able to find signs of it beyond our own little planet.

Unfortunately, the evidence has been elusive. It's seems as if one crucial ingredient has been missing. The most important requirement for life is liquid water, and that's the defining requirement for life in terms of our solar system. There's plenty of energy, there's plenty of carbon, there's plenty of other elements on all the planets in our solar system.

What's rare, and which, as far as we know, only occurs now on Earth, is liquid water. Liquid water is crucial because it's an ideal solvent. Molecules can easily move around in it and react with one another, allowing the complex chemistry of life to do its thing. For years, it seemed that Earth, with its oceans of liquid water, was an oddball and perhaps the only, place in the solar system where life had ever thrived. Then we started to look more closely at our neighbors.

In recent years, NASA spacecraft have sent back images of Mars with stunning detail, and there are clear signs of a watery past. From orbit around Mars we can see ancient rivers that are now dry, canyons which look like they had lakes in the middle of them, even what looks like an ancient ocean floor in the northern hemisphere.

We see unmistakable signs that Mars was a wet place.

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And now there's even more information from NASA's twin rovers that roamed the Red Planet, taking pictures and probing the rocks for their chemical makeup. The photos reveal clear sedimentary layers in the Martian rocks, and chemical analysis shows they must have been laid down in the presence of water. Mars might be too cold and dry to harbor life today, but if water was once there, then perhaps life was, too. And now, there's hope that life may thrive even farther out in the solar system.

I think Mars is the number one candidate for the search for life beyond the Earth, especially if we're going to find it soon. But we do have a backup plan, and in this case the back up plan is Europa, one of the moons of Jupiter. A little smaller than our moon, Europa is covered with ice, but there are cracks in its surface, perhaps signs of ice sheets floating on a deep ocean of liquid water.

What might be melting the ice is internal friction created by the gravity of Jupiter and its other moons. Europa's ocean is suddenly considered a potential home for life. The places where life can live and exist are far more extensive than we used to imagine. We used to think a life-bearing planet would be just like the Earth, and a little closer to the sun it would be too hot, a little farther away it would be too cold. And now we realize, "Oh, gosh, there's a place which has an ocean with three times as much water as the ocean of Earth, and the water is warm.

So the likelihood of life existing on planets in space has just gone up enormously. So, even though we've yet to find life elsewhere in the solar system or beyond, we're getting more optimistic that life may be widespread. But if life is common in the galaxy, what kind of life would it be? Is it merely the kind of life we had here for about three billion years, microorganisms happily brewing away with nothing bigger or more interesting than bacteria?

Or is it the complex plant and animal life we find in our oceans, of all shapes and sizes? Or could it be what SETI is banking on: We now know that the way we got to this, from something like this, was through evolution. Does that mean evolution would work the same way wherever life appears? Frank Drake thinks so. Once you have life, evolution goes to work. Life is very opportunistic. It finds ways to survive.

It finds ways to cope with changing environments. And in the process it becomes more intelligent, and in the long run you end up with something like us, exploiting technology to live in even more inhospitable habitats. Drake's optimism shows up in the estimates he's plugged into his own equation.

His guess is that wherever life arises, it will evolve into intelligent life 10 percent of the time. Not quite inevitable, but a fairly common outcome. It's hard to know how likely or common intelligence is, when it's shown up so recently in Earth's history. So the short history goes like this: And intelligent life, people like ourselves, technologically competent humans, that's just a snap in the full history of the planet. After about three billion years with only microscopic life, Earth finally became home to true plants and animals.

And after another five or six hundred million years, we came along. One of the major mechanisms for all these changes has been DNA, the long chain of molecules that carries the blue-print for every living thing. Every time a cell divides, its DNA makes a copy of itself, and in that copy, there are always some mistakes.

Sometimes those mistakes result in an animal or plant that's more successful than its parents. It's these kinds of mistakes that have allowed the tree of life to branch out in so many directions, creating the great diversity we see on our planet. Would aliens have DNA? Well, I would be surprised to find aliens with DNA as their heredity, because DNA is a useful molecule, it can replicate, it can do the mirror image bit, it can do the It's a very useful trick, but other chemicals can do that, and I'd be surprised if aliens latched onto the same one that we did.

To get from microbes to complex animals and intelligent life, you might not need DNA, but there's one ingredient that could be absolutely crucial for the evolution of intelligence, and it may be the rarest of all: Some scientists say that the key to our evolution was Earth's long and relatively peaceful history.

Among them is paleontologist Peter Ward. In this big galaxy of ours—hundreds of billions of stars—surely earth is repeated many places, many times. Well, I think the question is, "How much time do we have? So you've got a long period of time. Now that doesn't say you couldn't get it sooner at other places, but you still need finite periods of time. And to me that is the major argument against there being intelligent civilizations. You can't go from a bacterium to an intelligence in a million years, maybe not even ten million years, probably not even in a hundred million years.

How many other planets are going to have such long periods of time? Not many, I think. In the half a billion years when intelligence was evolving, Earth's plant and animal life might have been pushed back to square one, single-celled organisms, with one catastrophic event. At least a couple of times, we came pretty close. This crater, about a mile across, was made by a meteor that plunged to Earth nearly 50, years ago. As violent as that event must have been, it was nothing compared with earlier catastrophes.

Just ask the dinosaurs. The dinosaurs ruled Earth for about a hundred and fifty million years. They had the size. They had the power. It seemed that nothing could stop them. Then, sixty-five million years ago, an asteroid about six miles across headed toward Earth. In the aftermath of a collision of epic proportions and widespread volcanic eruptions, as many as two thirds of all living species were wiped out.

The big guys didn't stand a chance. Among the survivors were little mammals, and with the dinosaurs conveniently out of the picture, they thrived. Over the eons, their descendents evolved into lots of different animals, including primates, including us. That's how we got our start. But what if you turned back the clock? What if that asteroid had taken a slightly different course and missed Earth completely?

Little mammals may never have gotten their chance because the dinosaurs could still be in charge today. And instead of me, one of them would be hosting this show! In some ways, we owe our existence to serendipity, and some argue that this makes the evolution of intelligence far less likely. Our brains evolved through many stages: This worked for us, but is it the only route to intelligence? Would an alien species have to go through the same steps? There's no way to know for sure, but on our planet, lots of animals have remarkable brains and behavior, including some that are very distant from us on the evolutionary tree.

Among them are the cephalopods, including octopus, squid and cuttlefish.


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They're related to clams and oysters, but they don't look much like them at all. And in evolutionary terms, they've evolved in a very different way. Roger Hanlon has spent the last 30 years studying the behavior of these animals, behavior that is their main defense from ending up as dinner. These animals are a yummy hunk of protein swimming around in the ocean, and once they're caught, they have no defenses. So they have to have a good primary defense.

In the lab, Hanlon and his team study how cephalopods, like this cuttlefish, control and change their skin patterns. It's taking that visual information and translating it to the skin on the back. To see how they apply their tricks in their natural habitat, Hanlon tails them with his underwater camera. Finding them in the first place.

Octopus and cuttlefish have an uncanny ability to completely disappear into the background. We all think of the chameleon as sort of the king or queen of color change, but that's not true. A cephalopod can show many more patterns and can show them instantaneously. An octopus can be so camouflaged you literally cannot see it. So every place they go, they are morphing into something that looks a lot like that environment. So here's the scene. You've got a rock with algae all over it.

There appears to be nothing there except the swimming fish going by. Okay, so take a look here and just watch for a moment. This animal was completely camouflaged on that rock, and suddenly it was there. This remarkable camouflage, changing both pattern and three-dimensional texture, is performed by skin unlike any other animal's. It's an amazing skin, because there are up to 20 million of these chromatofore pigment cells, and to control 20 million of anything is going to take a lot of processing power. We call it a computer.

These animals have extraordinarily large, complicated brains to make all this work. For Hanlon, the brains and sophisticated behavior of these animals suggest that there's more than just one way to get smart. Even an invertebrate animal related to a clam or a snail can develop an incredibly complicated brain. This is one of the true wonders of nature. It's hard to explain why, but it's everywhere. And what does this mean about the universe and other intelligent life? The building blocks are potentially there and complexity will arise.

Evolution is the force that's pushing that. I would expect, personally, a lot of diversity and a lot of complicated structures. It may not look like us, but my personal view is that there is intelligent life out there. But intelligent life is not necessarily life we can talk to across the depths of space. For that, you need technology. As smart as an octopus or a dolphin is, neither one of them is going to build a radio transmitter or a space ship. When paleontologist Peter Ward looks at Earth's track record, the odds for technological aliens don't seem very promising.

There's maybe 30 million species on the planet today. And if we look at the fossils, there's hundreds of millions of species in the past, but only one of them which has risen to technology. It's happened one time out of hundreds of millions of possibilities on planet Earth—one time, one time only. So, that's an astronomically small number.

Here on Earth, we are the only species that has mastered technology. Since it's so rare here, should we really expect technology to be common among the aliens? Many would say "no," but the folks at SETI continue to hope. Searching for alien signals night after night can test anyone's patience, unless, of course, you find one.

Most evenings SETI will get a false alarm or two, but one night in , they received a signal so strong and true, it looked as if their long search might be over. We were observing at another telescope in West Virginia, and we got this signal that started to pass all the automated tests that we use to determine is it really extraterrestrial, is it just more interference?

Following standard procedure, she pointed the receiving dish away from the star where the signal appeared to originate: But when they moved the dish, the signal went away. And when it was pointed back at the star, the signal returned. Excited, the SETI team repeated the test. We went off in another direction, and the signal went away. And we came back and it was there. And we went off in another direction, and the signal went away. And it was now getting very interesting. Interesting because the signal might actually be coming from deep space. I was back in Mountain View. We were watching the signals on remote monitors.

Well, after about four or six hours of this, still passing the tests, needless to say, our blood pressure definitely was rising. And I was so excited that exactly what I was looking for was right there, staring me in the face. By now the star had set. The next night would tell the tale. If the signal returned, perhaps E. I, for one, couldn't sit down; I was sort of pacing around. A lot of people were huddled around the computers.

Nobody went out for a burger. In a sense, you know, it could have been an historic moment. The historic moment didn't survive the night. Unfortunately, the backup antenna wasn't working. So it took a little longer than usual for the SETI team to discover the truth on their own: The champagne remained unpopped. Despite the disappointment, SETI has never lost faith. Its scientists remain convinced that our universe is capable of producing intelligent life on many different worlds. I truly believe there are signals out there. I also recognize full well that our instruments, as powerful as they are, are hardly beginning the search.

The number of stars we've looked at, the number of radio frequencies, is minuscule compared to the total inventory of combinations of stars and frequencies there are to search. So we've hardly started. We should not have succeeded. Only through a great fluke of good luck would we have succeeded by now. Humans have been leaking radio waves into space for most of the past century. Compared to the history of our Milky Way galaxy, about 10 billion years, that's a tiny blip. And we've been actively listening for the radio signals from distant civilizations for only about 40 years.

If the aliens are on the other side of the galaxy, any signal they send could take tens of thousands of years to reach Earth. It's as if the aliens were throwing a dart and trying to hit one tiny spot on this enormous landscape of time and space. Let's face it, the odds of our capturing that signal aren't very good. For me, it's the most interesting question. What's our place in this universe? How do we fit in? Are we just run of the mill? Are we totally exceptional? Or are we somewhere in between?

Exploring our own world and the universe beyond has been full of surprises. Just a few hundred years ago, we assumed that everything about us and our surroundings was special and unique. Now we know there are lots of stars out there; many like our sun.

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We're discovering other solar systems with planets. And the chemicals of life, forged in stars, are abundant in the universe. If those common chemicals have caught the spark of life somewhere else, who knows how that life will evolve, what path it will follow, and whether we'll ever meet?

I feel almost embarrassed. I just feel that this is a question that is going to be so profound for us as a species, but also individually. Each one of us will have to look within ourselves and figure out what it means to us. We still don't know. But perhaps someday we will.

And the answer, whatever it is, will reshape our sense of ourselves and our place in the universe. The "Origins" series continues online. Then cast your vote. Find it on pbs. We see you reaching for the stars. Sloan Foundation to enhance public understanding of science and technology, and the George D. When and where did life gain a foothold on the early Earth, and how did it survive in such a hostile environment? How Life Began," zeroes in on the mystery of exactly how it happened. Join the hunt for hardy microbes that flourish in the most unlikely places: The survival of these tough microorganisms suggests they may be related to the planet's first primitive life forms.

Host astrophysicist Neil deGrasse Tyson deepens the search by investigating tantalizing and controversial chemical "signatures" of life inside three-billion-year-old rocks and meteorites found around the world. The early Earth was not a Garden of Eden. There were no clear blue oceans, there were no plants. There was no life at all. We think that all the carbon in your body arrived on the Earth in meteorites like this. So it makes you wonder: And if they did, how did they generate those first traces of life?

A walk on the ancient surface of the Earth offers clues. These are the oldest fossils in the world, at about 3. Life evolved on this planet very early and very fast. Journey back to an age when invisible microbes ruled the planet and caused the greatest transformation in Earth's history. Over a billion or two billion years, the amount of oxygen that these little creatures produced was enough to actually change the entire atmosphere of the planet. We see you inventing the next big thing. Microsoft is proud to sponsor NOVA, for celebrating the potential in us all.

In the endless reaches of the universe Earth seems unique. It's a planet shaped and molded by life, a planet that six billion people call home today. But when it was born, some 4. Covered in lava, and smothered in noxious gases, Earth was a planet under siege. If you were a human, going back into time, and trying to stand on the early Earth, it would be just like visiting a planet that was not your own.

This was a hazardous world, no doubt about that. If you were located in the wrong place at the wrong moment, you were simply vaporized. It was a planet plagued by catastrophe. If you condense all of Earth's history to just 24 hours, then only minutes after it formed, the entire globe melted and reformed. Then, to make matters worse, another planet about the size of Mars slammed into Earth, a cataclysm that created our moon.

But soon after these disastrous beginnings, the most radical transformation of all time hit the planet: So how did life begin? Well, over the years, people have come up with some pretty creative answers to this question. One of my favorites comes from a 17th century scientist who wrote down a recipe for creating life from scratch. Let's see, it says here, "Take a dirty garment, place it in a vessel.

Of course, we all know that life doesn't form this way. But at some point in the Earth's early years, life did emerge out of non-living ingredients. And for clues to the real recipe of life, we have to go back some four billion years to a time when Earth was nothing like the planet we know today. When we think of early Earth we must recognize it was not a Garden of Eden. There were no clear blue oceans, there was no clear water, there were no plants.

The young sun was weaker than it is today. And its light barely penetrated the atmosphere of carbon dioxide spiked with the pungent fumes of hydrogen sulfide. Since the atmosphere was thicker and dominated by CO 2 , the Earth had a reddish tinge to it. It didn't have the familiar blue sky. The oceans would have had an olive green color rather than our familiar blue color. For about the first million years, comets and asteroids pounded our planet, a time known as the "Heavy Bombardment.

These interplanetary missiles measured up to miles across. Their impacts vaporized Earth's oceans and melted its crust. With its extreme temperatures and toxic rain, seemingly nothing could survive here. But we now think that in this hellish environment, life first took hold.

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And today, hidden away in remote corners of our planet, conditions that in some ways resemble the extremes of early Earth can still be found. Penny Boston and Diana Northrup are microbiologists on an expedition to investigate how life can survive in those harsh surroundings. Buried in the depths of this tropical rainforest is a cave called Cueva de Villa Luz.

Located in southern Mexico, it's an underground world laced with hydrogen sulfide, a foul-smelling gas that was present on Earth some four billion years ago. These relic, or antique environments like Cueva de Villa Luz offer the same kinds of environments that we would have found on early Earth, and we're hoping to get clues to work backwards from those. As you approach the cave you begin to get these faint whiffs of the rotten egg smell.

And as you get closer this becomes more intense. Hydrogen sulfide is can be extremely poisonous, so the scientists have to wear gas masks inside the cave and carefully test them for leaks. At the levels at which humans can't live very long in hydrogen sulfide you don't smell it at all. It will just simply cause you to go unconscious and die very quickly. But can any other forms of life survive in the deep recesses of the cave so toxic to humans? Here, hydrogen sulfide, an invisible gas, escapes from the underground springs, reacts with oxygen in the water, and coats the cave with sulfuric acid.

The longer it sits there on the walls, the more acid it becomes. And so, eventually, by the time the drop is falling on you it's a very, very acid environment. It's very fatiguing, and even with the protective masks that we have, we pick up loads of toxic gas through our skin and perhaps through tiny leaks.

Amazingly, despite the extreme conditions, it appears that life is thriving inside the cave. It comes in a strange package: The snottites are drippy, gooey, mucusy formations that look like stalactites. And that's why they were called snottites, because they resemble strings of snot. We believe that the snotty, gooey stuff is to protect them against extreme acidity because when we measure the drips on the snottites, they are as extreme as battery acid.

And so, while we find that daunting, this is where they thrive. Bacteria are among the most primitive and most common organisms on Earth. Like all forms of life, they grow, adapt to their environment, and reproduce. Inside each single-celled bacterium is a molecule of DNA, the code of life which allows them to multiply. There are millions of bacteria in each snottite. And down in the underground streams, Penny Boston has found different kinds of bacteria in slimy clumps she calls "phlegm balls. In fact, the cave is home to a huge number of bacterial colonies.

And astonishingly, instead of being poisoned by the hydrogen sulfide, these bacteria depend on it for their survival. They take the hydrogen sulfide and they get chemical energy out of it. It doesn't poison them. It's home sweet home for them, and this is a pretty new finding for these organisms. Conditions on early Earth may have been far worse, but these bacteria suggest that primitive life could have thrived in extremely hostile environments. But where did the very first life come from?

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For more than a century, scientists have known that life is the result of chemistry, the combination of just the right ingredients in just the right amounts. Today, we know these ingredients aren't things like dirty garments and wheat, which people used to think would spontaneously generate mice. The ingredients of life are actually much simpler. All living things, from bacteria to mice to you and me, are made from a small set of chemical elements: Combined in just the right way, these are the fundamental ingredients of life, and carbon is the star of the show.

What makes carbon special is the kind of bonds that it makes, both with itself and with other elements. We know of no other atom that has the flexibility that carbon has to form diverse types of compounds. And the idea that life could have started when carbon and other ingredients combined in the harsh conditions of early Earth was first put to the test in the s by a young graduate student named Stanley Miller. To simulate the newborn Earth in the lab, Miller assembled a contraption made out of flasks and tubes. He filled one flask with gases thought at the time to represent Earth's primitive atmosphere, and he connected that to another flask with water to represent the oceans.

And then he did a brilliant thing. He simply put an electric charge through that to essentially simulate lightning going through an early atmosphere. And after sitting around for a couple of days, all of a sudden there was all this brown goo all over the reaction vessel, and when he analyzed what was in the vessel now, he actually had amino acids. Amino acids are compounds that form when molecules of carbon and other elements link together. They are the essential building blocks of proteins and cells, vital ingredients of all living things. Stanley Miller's experiment was headline news and jump-started the scientific search for the origins of life.

Life is really chemistry; there's no question about that. In fact, it's a chemistry that, when you get the recipe right, it goes, and it goes fairly quickly. That recipe is hotly debated today, and most scientists think the environmental conditions on early Earth were very different from the ones Miller simulated in his lab. And another debate rages about when this recipe first got cooked up. On our hour clock, the barrage of asteroids and comets lasted from about midnight until almost 3: The assault then weakened, but continued for more than million years. It's hard to believe that life could have gained a foothold during this unstable period, but new discoveries reveal that life may have existed as early as four in the morning, or about 3.

The evidence comes from some of the oldest rocks on the planet, found in the remote regions of West Greenland. The geology of Greenland is unique. It contains a record of some of the earliest geological processes that we know of on the Earth. The rocks themselves are thought to be between 3. These rocks are so old that any fossils they once contained have been destroyed.

So to find out if life existed when they formed, Mojzsis had to look for evidence that is far more elusive. There may have at one time been small fossils, microfossils but under the conditions of heat and pressure that these rocks experienced, such fossils would have been disaggregated and destroyed. So what we have left behind then are chemical fingerprints of ancient bacteria or microbes.

To search for those fingerprints, Mojzsis first extracts a sample from the ancient Greenland rocks. Then he will analyze its chemical composition looking for carbon, a signature of life. But carbon comes in several different forms. And Mojzsis wants to know if the carbon in this sample is the kind left behind by living creatures. If so, he believes that life may have existed when these rocks formed over 3. It was a surprise for us to find evidence of ancient life in these rocks. We didn't know if it would be there. You know, just because the stage is set doesn't mean that the actors are present.

But these samples, here, represent the first evidence we have, direct evidence of a biosphere on our planet. If it emerged so early, life was lucky to miss the greatest cataclysm of all time, an impact like no other in our planet's history. It happened when another rocky sphere about the size of Mars collided with Earth. The outer layers of our planet were vaporized, and the debris from this collision coalesced to form the moon.

That impact was so powerful that any building blocks of life that existed on Earth would have been destroyed. This gives rise to speculation that the ingredients of life didn't form on Earth at all, but arrived special delivery, from outer space. Hollywood has always been taken with the idea that life came from outer space. But it's not as far-fetched as it might sound. Space is not very far away. Space is only about 20 kilometers that way.

Now, that's very close and space is vast. And a scientist named Don Brownlee designed an experiment to find out if space might actually harbor the building blocks of life. There are 40, tons of bits of comets and asteroids that impact the Earth every year. This is mostly in the form of particles that are less than a millimeter in size.

We breathe them, they're in the food that we eat, but they are very difficult to find. You can only find them in very special places. To see if this shower of space-dust contains the ingredients for life, Brownlee needed to obtain samples uncontaminated by Earth's atmosphere. So to get just a few micrograms of dust, he commissioned a former spy plane to fly close to the edge of Earth's atmosphere.

Sticky pads on the plane's wings collected the space dust. Then, Brownlee's colleagues sliced the dust particles into slivers less than one-tenth the thickness of a human hair. And they discovered that these tiny particles are rich in the seeds of life. If you look on an electron microscope, you'll see this wonderful array of minerals and carbon and organic materials that are 4. And this extra-terrestrial dust isn't the only possible source of life's ingredients.

In a region of space called the Asteroid Belt are huge amounts of debris left over from the formation of the solar system. And sometimes, chunks of debris containing metal and rock fall to Earth bearing surprising gifts. It's a gold mine, this little chunk of meteorite which fell on Australia last year. For the past six months they've been taking it apart and have discovered that it contains amino acids, the building blocks of life. It was the first time that complex organic compounds had ever been found in material from space. And if meteorites like it were common perhaps they had delivered vast quantities of the original constituents of life to early Earth.

Enough organics are present here that we think that meteorites like this provided the early Earth its entire budget of organics. So all the organics in your body, all the carbon in your body and in your lunch you had today, arrived on the Earth in meteorites like this. If they come through the atmosphere in large enough objects, they're like little capsules coming in the atmosphere.

They break apart on the Earth's surface and deposit their cargo of organics. More than 70 kinds of amino acids have been found in meteorites, and many are the fundamental ingredients of proteins that make up living cells. During the Heavy Bombardment, millions of meteorites may have seeded the Earth with the stuff of life. And there might have been an even more efficient delivery system. Comets are like giant dirty snowballs made of ice and rock. Some comets that hit the early Earth were the size of mountains, and a large portion of their mass could have contained organic compounds.

The destructive power of comets and meteors is astronomical. The meteor that slammed into Earth some 50, years ago, here in Arizona, blasted a hole in the ground nearly a mile wide—from here to here—and so deep it could hold a story skyscraper. And as if that weren't enough, the force of the impact was so great that it instantly vaporized nearly the entire meteor, three hundred thousand tons of it. And just what happens to things like amino acids when they slam into Earth with such devastating power?

To answer those questions, one scientist came up with an ingenious experiment. Using a huge gas-powered gun, Jennifer Blank simulates the extreme pressures and temperatures that are unleashed when a comet smashes into Earth. We set out to test whether or not materials would survive or whether they would break down. And we expected that, or we were hoping that, some fraction would survive. We figured the parts that didn't survive would break down into smaller components, but in fact what we found is much more exciting.

The gun fires a bullet at 5, miles an hour towards a sample that represents the organic molecules inside a comet. The sample consists of a solution of five different amino acids, two of them present in every living cell. The mixture is inserted into a steel capsule. The gun will send a shockwave through the capsule simulating the extreme pressures of a comet's impact. I think it's very hard to just imagine what kinds of pressures we're generating in these experiments.

If you think about going to the bottom of the ocean, the pressures you'll have there are only a hundred times atmosphere. So these are hundreds of thousands of times atmospheric pressures. Will Jennifer Blank's experiment show that the building blocks of life can survive a crash landing on Earth? Okay, bringing up the X-rays Three, two, one, fire. When they remove the capsule it's undamaged.

But have its contents survived the impact? The once clear solution of amino acids has turned a tarry brown color. And the analysis revealed that not only had the material withstood the colossal pressure of the impact, but it had transformed into a new compound. Amino acids, combinations of carbon and other basic elements, had fused together to form more complex molecules called peptides. We went from our initial small compounds—and here's an example of one of them, a simple amino acid—and we used the energy associated with the impact to build larger molecules.

Molecules like this—this is a peptide—and we show that we can use the impact energy to grow larger molecules from the simplest building blocks of life. Peptides link together to form larger building blocks, proteins, which make up all the cells in our bodies.

But the leap from non-living ingredients to a living creature, complete with DNA which allows cells to replicate, is staggeringly complex. It is hard to really get your head around the great leap from non-living to living. Well, it's hard enough that nobody's succeeded in doing it in the laboratory. I think it's an astonishing mystery, and one that we truly don't understand in any great detail. While we don't yet know how the spark of life occurred, we can try to figure out where it might have gotten a foothold.

And because the planet was under such devastating assault from comets and meteors, the leap to life may not have taken place up here on Earth's surface. To take hold, life may have needed a safe haven, perhaps underground. A team of scientists descends into one of the deepest mines on Earth to investigate whether microbial life can survive far below the Earth's surface. And the mining environment gives us this fantastic window into the deep subsurface.

It's a unique scenario because there is nowhere else on planet Earth that allows you to have access to that sort of sample location at two, three, three and a half kilometers deep. It takes 45 minutes to reach the heart of this South African mine. Conditions here are extremely uncomfortable, for humans, that is. The temperature of the rock is degrees Fahrenheit, and the air pressure is twice that at Earth's surface. Life down here survives entirely without sunlight. If they exist, microbes need to find a way to live in pitch darkness, drawing chemical energy from water and minerals trapped in the surrounding rocks.

Microorganisms have been shown potentially to be able to use these molecules to provide themselves with energy and support themselves completely independent of photosynthesis. And if we can prove that that is the case here, then that is very interesting because that adds credence to the idea that you could have life originating in the deep subsurface.

As the miners drill into the rock, they break into ancient pockets of water, havens for microorganisms. We're not sure how organisms can live in such extreme environments. The major thing is there's such low nutrient availability, there's nothing really for these guys to continually use and process to survive, and yet somehow they do. And the question is, "How do they do it? The first step is to collect pristine samples of the water and see if they can grow the microbes it contains.

I'll get a very big sense of achievement if I can actually take something that's been isolated for million years, put it in the laboratory and actually find out what it is this organism needs to survive. In a makeshift lab near the mine, the team attempts to recreate the environment deep inside the rock. And they have found that these microbes are dining on a variety of strange gases. It turns out that in the deep subsurface there's an abundance of methane gas and ethane and propane.

Now, for you and I that's not a very exciting diet, but what we think is that these organisms may be taking that kind of gas and actually using that as a food to survive. On such an exotic diet, the bacteria draw just enough energy to divide and reproduce only once every thousand years, suggesting a way that life could have survived deep beneath the surface of the early Earth. And the Earth's crust may not have been the only place where life could have hidden from the Heavy Bombardment.

Another safe haven may have been the ocean. Volcanic activity was intense on the early Earth. Chemicals from deep inside the planet spewed into the primitive seas. Even today, marine biologists have discovered volcanic vents on the ocean floor. Despite scalding temperatures, acid eruptions and total lack of sunlight, they found creatures of all types thriving down here. And at the bottom of the food chain are microbes that live on the noxious hydrogen sulfide gas erupting from the vents. If all of the bombardment was occurring near the surface, survivors would be existing in just these kinds of hydrothermal vent communities where there's abundant water and nutrients and heat and food in the form of chemical energy.

It has been found that organisms collected there nowadays are genetically akin to some of the earliest organisms that we think existed on the Earth. By about three and a half billion years ago, or five o'clock in the morning on our hour clock, the bombardment of asteroids and comets had ceased.

With far fewer violent impacts on Earth, microbial life could now survive outside its protective hiding places. After it reaches Earth's surface, life would take advantage of another source of energy: Up here, microbes evolved a green pigment known as chlorophyll. This allowed them to trap sunlight and use it to drive a chemical reaction that converts carbon dioxide and water into food.

Called "photosynthesis," it was a clever invention that enabled some bacteria to grow and reproduce almost without limit. Once it started, photosynthesis was a runaway success, and today it's how all green plants make their living. As Earth cooled, this new generation of cells spread across the oceans. Immense colonies of green slime would take over the world, kicking off the greatest transformation in our planet's history. Photosynthesis is the great liberator of biology.

With photosynthesis, the energy is coming from the sun, and life could spread, literally, over the entire planetary surface. And this remote corner of Western Australia holds clues to how that happened. These domed structures, called stromatolites, are built up layer by layer over thousands of years by tiny microbes. These microbes may be similar to life forms that dominated our planet billions of years earlier. And in the arid hills nearby, there may be evidence of these ancient creatures.

These rocks have remained unchanged for three and a half billion years. Here it's possible to walk on the surface of early Earth. Martin Van Kranendonk spends months at a time in this wilderness, studying the geology and producing maps. In a secret location in these hills is what could be one of the greatest geological discoveries of all time.

These are the oldest fossils in the world, at about three and a half billion years old, and they're composed of stromatolites. And at this outcrop we can see two different types of structures that these creatures formed. First are these black mats that have wrinkly textures all through it, and the second are these larger domes that form these broad structures.

The most likely way these things formed is by the growth of microbes. Like modern stromatolites, these ancient structures could also have been built by colonies of bacteria. And not far away are fossilized ripple marks which suggest they might have grown in shallow water. And here, you can see we've got a smaller structure that we call the "Mickey Mouse Ears," which is this beautiful doubly branching structure. And there is nothing else that we can think of which would make that except something that was growing on the bottom of the ocean.

So perhaps the ancient stromatolites were formed by microbes like the ones that build these structures today. These big stromatolites are composed mostly of rock at the bottom, and the only living part of the stromatolite is a thin layer on top. And that thin layer on top is made up of microscopic blue-green bacteria called "cyanobacteria. Named after the blue-green color of their cells, these cyanobacteria use photosynthesis to collect energy from the sun.

They secrete a sticky coating to shield them from ultraviolet radiation. As tiny pieces of dust and sediment settle on top of the sticky cells, the bacteria migrate closer to the surface to reach the light. The layers of sediment build up by about half a millimeter a year. These structures contain living microbes, just as they have for thousands of years.