字幕表 動画を再生する 英語字幕をプリント They're dazzling, priceless... at times, even glowing. How can one not fall in love with rocks and minerals? I mean, the colors, the shapes... ...and they're the building blocks of modern civilization. We wouldn't have televisions, we wouldn't have automobiles, we wouldn't have buildings without the mineral riches that we have. But could rocks and minerals also solve the greatest mystery of all time? The origin of life. The rocks we pick up tell a story that life couldn't have occurred without rocks. Could cold, lifeless stone hold the key to every living thing on Earth? From Australia, to Morocco, Nova goes around the world and back in time to investigate the origin and evolution of life. Look at a rock and you think ah, well, nothing. but this holds the signature of life. From its first spark... People were saying they've made Frankenstein in a test tube... ...To the survival of the fittest. These were immense creatures. Sharks that may have been 50 or 60 feet. Was it the secret link between rocks and life that made the difference? Life's rocky start. Right now, on Nova. The ancient market of Marrakech, a chaotic, colorful gathering place teeming with life for thousands of years, the perfect place to ask how did this exotic, beautiful and sometimes bizarre thing called life, begin? How did Earth go from a lifeless, molten rock... to a living planet? Full of diverse and spectacular creatures. it's a question that has long perplexed scientists. Now, Robert Hazen, a geologist, is trying to show we are missing an essential ingredient in the recipe for life. -look at that vein of calcite... Rocks. Nothing seems more lifeless than a rock. it's inanimate, it's the antithesis of a living thing, but we're beginning to realize that rocks played an absolutely fundamental role in the origin of life. Hazen is out to expose a secret relationship between rocks and life that helped drive both the origin of life and its evolution into complex creatures. This is a very new set of understandings and the more we look, the more we see that life depends on rocks, rocks depend on life. This has been going on for four billion years. As a geologist, it's no surprise that Hazen is searching for answers written in stone. But is he right? Are rocks the missing spark of life? The history of Earth is unimaginably long. If it were sped up to the equivalent of a single day, all of humankind from the earliest skeletons to the invention of the iphone would have occurred in only the last four seconds. Dinosaurs were still roaming earth about 20 minutes before that, but the creation of our planet occurred more than 23 hours earlier, two cycles on this clock or 4.5 billion years ago. Comprehending Earth's vast history is a formidable task. It is four and a half billion years of change, but you can divide it into half a dozen ways of describing Earth through time. Bob Hazen has come up with another way to visualize Earth's long history that reveals this special relationship between rocks and life. He has divided it into six stages, each represented by a different color to understand how we ended up with green earth, the planet we now know, requires us to turn the clock back to before there was any life at all. Stage one was the creation of black Earth. Back in Morocco, Hazen and Adam Aaronson, a meteorite expert, seek out a small rock from the beginning of our cosmos. -Wow look at this pile here. -yeah. These are meteorites. Rocks that have fallen from space. -This is Tamta. This is the one that fell 20 kilometers up the road from here. People saw it fall. A recent meteorite fall in Siberia was captured in videos that have shown up on Youtube. Other space rocks have ended up for sale here in Morocco. -Say you'd buy this without doing tests... -I'll drop the cash right now here and give me a good price. Meteorites here can sell for tens of thousands of dollars. That may seem a steep price for a lump of rock, but these are some of the very oldest objects in our solar system. This is the oldest object you could ever hold in your hand. It's 4.6 billion years old and is formed before Earth formed. This is the very first solid material, the very first rock in our solar system and these came together to build all the planets. Our Earth was created out of the rocks and dust present at the start of our solar system. Over time, small fragments of orbiting rock collided, coming together into the planet circling the Sun. At first, Earth was molten with temperatures in the thousands of degrees, but in the cold vacuum of space this hot rock began to cool and change. Nothing. Not a speck of dust is believed to have survived from the period of black Earth. It was a hellishly unpleasant time. Volcanoes spewed hot lava from deep inside the planet. When it cooled, it covered Earth with its first rock called basalt and it was black. It seems like a desolate landscape, but some ingredients that life will need are already here in these rocks. Look inside and you begin to understand how intriguing even an ordinary rock is. Every rock, you slice it open you look inside, there's something special. Rocks are made up mostly of minerals, which are crystals like quartz or diamonds. Looking through a microscope at super thin slices of a rock lets you see its mineral composition. This is the rock Peridotite, made up of small crystals, including olivine and pyroxene. Even a simple black basalt rock, spewed from a volcano, becomes a patchwork of colorful minerals. It's sort of like a fruitcake, you know I slice it open, there's nuts and there's dried fruit and maybe some lemon peel. It's made of lots of little things and it is not until you slice into that fruitcake that you see all the stuff inside that makes it special. What makes them special is not only their beauty. Minerals have remarkable chemical and physical properties and are a source of many of the elements - nature's building blocks. That is why they are essential in our modern world to make everything from skyscrapers taller - mobile phones smaller. Extract the element molybdenum from the mineral molybdenite to make steel stronger. Or add a pinch of cobalt and your iphone battery will last longer. Minerals are the fundamental building block of societies. We wouldn't have televisions, we wouldn't have automobiles, we wouldn't have buildings without the mineral riches that we have. So, were the remarkable chemical properties of minerals also key in creating life? If so, Earth would mean more than it started with It's estimated that the meteorites that formed Earth had only about 250 minerals, sort of a chemical starter kit, containing many of the elements. Then, in the intense heat and pressures in the creation of our planet, new minerals began to form. This changed the appearance of our Earth from black to gray. Yosemite national park is a relatively new piece of Earth, but the kind of rock that makes up these dramatic cliffs goes back much further. These huge walls are granite containing minerals like quartz and feldspar. Granite became the foundation of our continents, leading Earth into the gray period. At this point, earth is still a long way from the glorious diversity of plants and animals that makes Yosemite so picturesque. But the stage is set for the next character in our planet story: Water, which will turn Earth blue. Water plays a central role in every model for the origin of life. That's because water is such a great solvent. All these different kinds of molecules can be floating around the water and then they have the potential to interact together. The starting point is the water. So when did Earth cool enough to have liquid water, this element key to life? One of the biggest unknowns in this whole idea of going from black to gray to a blue water-covered earth, is how quickly it happened. The timing is a big mystery. The Pilbara in Western Australia is one of the oldest places on Earth and so, one of the best places to solve the mystery of the planet's first oceans. Hazen joins an all-star team of geologists, including Martin Van Kranendonk from the University of New South Wales and John Valley of the University of Wisconsin. Valley is collecting rocks that could hold clues to when water first appeared. We could get zircons and other minerals that date all the way back to 4.4 billion years old. Hopefully. Some rocks here contain sand-sized grains that wheathered from even older rocks. one in a million, literally, is a crystal called zircon, one of the longest lasting materials in nature. Zircon is a popular gemstone, but the microscopic zircon found here is even more precious. Zircon crystals are especially amazing. Gemstone zircons of course are valued, but these tiny ones the geologists value are microscopic that make a lousy ring, but they tell an incredible story. To tell that story, John Valley must first find the tiny crystals, the ultimate needle in a haystack. If you want to find a needle in a haystack, the first thing you do is you burn down the haystack. Then you sip through the ash to look for the needle. Rocks are pulverized into sand sized grains and sorted by weight in a machine developed to pan for gold. The gold that Valley is looking for are heavy zircon crystals which get channeled into different tracks. Then, grain by grain, with a very steady hand, thousands of small crystals are sorted and analyzed. The chemical structure of a zircon crystal holds evidence of both the environment and the age when it formed. Some of these tiny crystals go very far back, just over a hundred million years after Earth formed. They are the oldest pieces of Earth ever discovered. So they could shed light on what our young planet looked like. It's totally amazing. To hold this grain of sand in the palm of your hand is literally to see back through time. It is a time machine. Valley expected these crystal time machines would confirm the long-held view that the young Earth was covered in molten lava, still cooling after its violent formation. I think the zircon on the left looks very promising. So what he discovered was shocking, because this type of zircon created 4.3 billion years ago could only have formed in the presence of liquid water. But how could there be water if Earth was still hot and hell-like? The implications were that the early Earth had water, it was cooler and it was wet. It's starting to look very much more familiar. And if water is a key starting point for life could there be life that early too? The science of the zircon is telling us that the Earth for a very, very long time was a habitable environment, not necessarily that there was life then. We don't know that yet, but there's no reason why there couldn't have been life as early as 4.3 billion years ago. So, if life were possible that early, it begs the question: how did life begin? In 1871, Charles Darwin speculated in a letter to a friend that a warm little pond might be life's birthplace. A warm soup of chemicals bathed by energy from the Sun would have been, well, comfortable for molecules to come together in new ways and create life. Darwin was way, way ahead of his time. A nice little warm soup is gonna get you a long way. Jeff Boda of the Scripps Institution of Oceanography in San Diego has spent his career working to understand the early Earth's soup of chemicals. He began under the direction of perhaps the most famous scientist in origin of life research, Stanley Miller. There are in the history of science turning points where we suddenly see the history of Earth and life differently. In the early nineteen fifties, Stanley Miller, the eager graduate student, and Harold Urey, the Nobel Prize winning mentor at the University of Chicago conducted this astonishing experiment where they made an early Earth environment. It looks like this sort of a Frankenstein type apparatus, but actually it's a very carefully thought out design. Boda sets up a modern-day test of the nineteen fifties experiment on Miller's original lab equipment. One flask contains water. That's to simulate the ocean. The other flask has just got the gases in it, so this is the atmosphere. Just as it does in nature, water from the ocean evaporates and rises into the atmosphere, where it condenses and returns to the ocean. Miller simulated what he believed to be the atmosphere of early Earth with different gases like ammonia and methane. Then he added a spark of genius. Miller and Urey decided to use a spark to simulate lightning, because that's such a ubiquitous process in the atmosphere of the Earth. That was the real inspiration. These little electric sparks that acted like simulated lightning. The energy from the spark of lightning breaks down the gas and water molecules so they can undergo further chemical reactions. To their astonishment, when they turn this apparatus on, after only a couple of days, you started seeing this pink color developing. In a few more days, black oily goo is forming around the electrodes. The electrodes get covered with new substances. Organic compounds, usually associated with life. And it wasn't just any organic compound. It was amino acids that make proteins, the ingredients for life. Amino acids are the building blocks of life. They form proteins, which are the key component of muscles and other tissues. People thought "aha!". This is a key step in the origin of life. And you really believe that you can bring life to the dead? That body is not dead, it has never lived. I created it.