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00:00Welcome to the future.
00:07PBS Digital.
00:13Next on Exploring Space.
00:17I think that the question of whether there is intelligent life beyond Earth
00:21is essentially the same question as whether there is life beyond Earth.
00:25And the thought that in this incredible enormity that we are the only creatures able to look at it
00:32and understand something and then talk about it, that would be a very discouraging thought.
00:37That would be a depressing thought.
00:39Ultimately we're only around until the next big impact and then human civilization is gone.
00:44Some time in the future we are going to be sending a submarine into an alien ocean searching for life.
01:02Fundamentally the biggest challenge to getting humans to Mars is money.
01:11The technology is here. We can do it.
01:14I see Mars as the first testing ground of the possibility that life has a future in space.
01:24Exploring Space. The Quest for Life is made possible by...
01:31A grant from the estate of Sperry H. Goodman.
01:46And by contributions to your PBS station from viewers like you.
02:12RCL, report range go for launch.
02:14Range is go for launch.
02:16LCL, this is LVD, you go for launch.
02:18Roger.
02:19July 2003.
02:22On.
02:23The United States prepares to send a robotic Land Rover to explore the planet Mars.
02:2820 seconds.
02:30The quest, to hunt for water.
02:33And for signs that humans are not alone in the universe.
02:37T minus 10, 9, 8, 7, 6, 5, 4, 3, 2, main engine start.
02:48Zero and liftoff of the Delta rocket with opportunity.
02:54The transients at liftoff.
02:57Engine position looks good.
03:01Recovering nicely from the liftoff transients and the solid rocket motors are increasing their thrust during their 75-second burn.
03:08The heavens above have long been a target for exploration for determining humanity's role in the great scheme of things.
03:20Some find the answers in religion and spirituality.
03:24Others find comfort in the hard facts of science.
03:29Earth may be a rare environment, uniquely designed for nurturing living organisms.
03:35But as humans explore the creation of the planet, the realization grows that the answers to the origins of life may lie beyond earthly bounds.
03:47Nobody knows how or when life began on Earth.
04:00And really the only way that you can begin to evaluate when or how life began is by examining the geological records.
04:09Dr. Steven Mojess of the University of Colorado is examining some of the planet's oldest rock here in Greenland at the top of the planet.
04:19When Earth was originally formed, it was a ball of molten rock so hot no organic materials containing living organisms could have survived.
04:28As it cooled, the Earth would have consisted only of sterile oceans and barren rock.
04:40The early Earth's surface was not rich in organic compounds.
04:45It was a surface that was dominated by compounds that are not particularly helpful to get life started.
04:53And if no organic material could exist on such a barren planet, life on Earth may have started elsewhere.
05:02My personal opinion is that since space is so rich in these organic compounds, it must have played a role.
05:11I don't think it's unreasonable to invoke the space medium as a source area for raw materials to get life started.
05:20Because after all, space is close.
05:23Space is only about 30 kilometers that way.
05:28All you have to do is take material from up there and bring it here.
05:33That's not far.
05:35And that is an infinite resource.
05:44More than four and a half billion years ago,
05:47the solar system was formed from huge clumps of ice, dust and rock left over from the creation of the universe.
06:04These clumps, called planetesimals, collided, growing in size as the larger planetesimals drew in smaller objects.
06:12Planet Earth was born from these molten collisions.
06:15The smaller objects not absorbed during the planet creation process were drawn to the outer edges of the solar system.
06:43There, just over three light years away from the sun, these comets and asteroids turned into an immense cloud called the Oort Cloud.
07:02The solar system, with its sun and planets and stars and Oort Cloud in tow, circles the Milky Way galaxy once every 225 million years.
07:17However, the 200 billion stars in the galaxy don't follow uniform circular orbits.
07:24They shift with each revolution.
07:26That sometimes brings the sun and the Oort Cloud into close contact with other stars and interstellar clouds.
07:34These close encounters can disturb the Oort Cloud, spinning comets trailing long tails of cosmic debris out of their normal orbit and directly into the Earth's path.
07:46These occur when the star comes very close to the sun, perhaps within 3,000 astronomical units, where an astronomical unit is the Earth's distance from the sun.
07:55Or, when we encounter a giant molecular cloud in the galaxy.
07:58These are very large clouds of interstellar gas where stars are forming.
08:02And these can really shake up the Oort Cloud and throw many, many comets in, in what we call a comet shower.
08:12These comet showers figure into one of the Aboriginal myths of creation.
08:21For some Aborigines in Australia, this is their Holy Land.
08:26The birthplace of humankind.
08:32A link between Earth and the heavens above.
08:36For these Aborigines, each star in the Milky Way is a dancing goddess.
08:42The legend goes that long ago, one of the goddesses lay her baby in a cradle to rest.
08:47But the cradle rocked.
08:50And the child fell to Earth.
08:52The impact left this jagged, three-mile-wide crater in the desert of the Australian interior.
08:59And, so the story goes, created life.
09:03Scientists of today think those Aborigines may well have got it right.
09:09Impact craters like this sprinkle the globe.
09:12Evidence of massive collisions between asteroids and comets and planet Earth.
09:19Scientists now believe these stellar collisions brought to our world organic elements of life from deep and outer space.
09:27Creating the rich and varied tapestry of living organisms we've come to view as what makes Earth unique in the universe.
09:35Instead of photographing Soviet missile silos, this former U-2 spy plane roams the skies above, collecting dust.
09:52I'll be right back.
09:54Space dust.
09:55Earth's atmosphere is full of microscopic material shed by passing comets.
10:11Comets. While cruising at 65,000 feet, 12 miles high, the pilot will deploy these oil-coated
10:20plexiglass plates. For every hour aloft, one of these plates will catch just a single particle
10:27of space dust. These particles are debris coming off the trail of asteroids and meteorites.
10:34Called micrometeorites, they weigh a mere one-billionth of a gram, hitting the Earth at a rate of
10:46one particle per square meter per day.
10:49Well, the particles have told us a very interesting story.
10:52University of Washington astronomer Dr. Donald Brownlee is the father of micrometeorites.
10:58Brownlee believes these dust particles, also known as Brownlee particles,
11:03hold the answer to the origins of life on Earth.
11:07These, we believe, are the most primitive materials in the solar system.
11:11And they are materials that are created along with ice to form cometary bodies,
11:15and also perhaps asteroids in the early solar system.
11:18And they are, in fact, preserved pretty much in the shape that they were
11:22when they formed four and a half billion years ago.
11:26Brownlee is searching for microscopic organic materials embedded within the Brownlee particles.
11:36Organic materials from deep space that may have been the first living material to arrive on Earth.
11:42So they have a very large organic carbon content.
11:46And we believe that this carbonaceous material is certainly a major contributor to organic material on the Earth.
11:56Right now, at present times, there are thousands of tons of this organic material falling on the Earth every year.
12:02And early in the history of the solar system, when life was forming about 3.9 billion years ago on Earth,
12:09the flux of this material was probably even much higher.
12:12So this has been a natural source of organic material falling on our planet throughout its history.
12:17And it may have played a major role in the origin of life. We actually don't know.
12:24To understand the role early comet showers may have played in bringing life to the planet,
12:30scientists look first to the Earth's cosmic sidekick, the Moon.
12:36The lunar surface is completely pockmarked with craters.
12:40Each divot indicates where an interstellar object, such as a comet, crashed into the Moon's surface.
12:46The Moon is close to the Earth. We're like father and child.
12:50And whatever is happening on the Moon is happening here on Earth, too.
12:53The problem with the Earth is that we have erosion, we have the atmosphere, we have plate tectonics.
12:59There's not much of a record left from the last 3 billion years on the surface of the Earth.
13:04But our neighbor, the Moon, preserves a beautiful record of everything that's happened to it over the last 3 billion years.
13:10So the presumption is, and nobody disputes this, that the impacts on the Moon are a good reflection of what's been happening on the Earth.
13:19And that's really what our interest is.
13:22When the U.S. spaceflight Apollo 14 touched down on the Moon in February 1971,
13:37astronauts Alan Shepard and Edgar Mitchell scurried through the gray lunar dust,
13:42collecting geological samples from craters on the lunar surface.
13:45Discovered within these samples were a multitude of microscopic glass beads.
13:54When a comet hit the Moon, the lunar rocks melted and scattered.
13:58When the liquefied fragments cooled, they solidified into these tiny glass droplets.
14:04Richard Mueller's team of researchers at Berkeley are dating these glass beads,
14:10enabling them to determine the age of nearly 150 different impact craters on the Moon.
14:16Knowing the age of these lunar craters gives Mueller an idea of the age of the craters on Earth.
14:33Prevailing scientific theory states that the number of impact craters should decrease over time,
14:40as space debris resulting from the creation of the universe becomes less abundant.
14:45Mueller's data confirms this theory is true for the Moon,
14:48so Mueller believes it is also true for craters impacting the Earth.
14:53Cratering comes about because there's debris in the solar system,
14:56and eventually we bump into it.
14:58The amount of debris decreases slowly with time,
15:01and so we expect a number of impacts to go down with time.
15:04But then to Mueller's great surprise,
15:06the glass beads began to indicate that 400 million years ago the cratering rate increased rapidly.
15:14No one knows why.
15:16That means the Earth also underwent this increase 400 million years ago
15:21to a level that was much higher than it had been for 2.5 billion years.
15:25Initial form of life developed in that 2.5 billion years to some very primitive life forms,
15:31but most of evolution took place during this period of 400 million years,
15:36when the bombardment was three to four times higher than it had been previously.
15:40This certainly played a role in the evolution of life on Earth.
15:44When a graph of the cratering rate on the Moon is superimposed on a graph showing the number of species on Earth,
15:59the increase of both happens simultaneously.
16:03This points Mueller to the hypothesis that diversification of new species on Earth was stimulated by cosmic impacts.
16:11The same result did not happen on the Moon,
16:14because the lack of a lunar atmosphere and lunar water precluded the ability for life to form.
16:20Many of us grew up believing that survival of the fittest meant the competition of one species with other species,
16:29and the stronger species won.
16:32When this catastrophe takes place, you may be very good at competing with other species,
16:37but unless you're adapted to survive the catastrophe, you really can't endure.
16:42There's an added advantage to flexibility, to adaptability.
16:47These are just the sort of traits that, for example, intelligence brings with it.
16:52It may be that the existence of these catastrophes, impacts on the Earth,
16:58is what's driven evolution towards a higher intelligence and flexibility.
17:02The most flexible animals on the Earth right now are humans.
17:13250 million years ago, the continents on Earth formed one giant landmass called Pangaea.
17:20The red dots on this map show the confirmed locations of impact craters here on Earth.
17:27Over geologic time, Pangaea broke apart,
17:30and the continents drifted in a process called plate tectonics.
17:34This shifted the location of most impact craters and buried some.
17:41Despite the constantly changing geography of Earth and the withering effects of erosion,
17:46the ages and locations of nearly 200 craters have been discovered so far worldwide.
17:5565 million years ago, it is widely believed a single comet or asteroid crashed down into the Yucatan Peninsula of Mexico, wiping out the dinosaurs.
18:0530 million years later, a smaller impact eradicated nearly all life along the eastern seaboard of the United States.
18:17So right here, we're standing above the rim of the crater.
18:20You can imagine that this arch of the beach here, if you could see down 500 meters beneath this surface, you would see the edge of the crater.
18:28What today is the heavily populated area surrounding Chesapeake Bay in Maryland once was tropical forest covering the mountain slopes and lush shoreline.
18:47The sea level was higher than today, and the world is much warmer.
18:56Large rhino-like mammals and hippopotamus-type creatures had come to dominate following the dinosaur's extinction.
19:04Just off the coast, gigantic prehistoric whales plied the oceanic waters in search of food.
19:12But then, what happened next shows the devastation a comet or asteroid traveling at supersonic speeds can wreak on Earth.
19:31In a flash of light, millions of people can wreak on Earth.
19:34In a flash of light, millions of people can wreak on Earth.
20:00In a flash of light, millions of tons of rock must have been pulverized.
20:04The 60,000 degree Fahrenheit blast sent molten shrapnel back into outer space,
20:09which then came back with devastating results.
20:13animals and plants in the immediate vicinity within 600 miles of blast would have been devastated.
20:32Locally, the region would have appeared dead.
20:57The region would have appeared dead.
20:59But the climatic disruption would have spread across the northern reaches of the globe.
21:04Life would return to this region only very slowly.
21:06But cosmic impacts may not be just about devastation and mass destruction.
21:25The Ames oil field is one of the most productive oil deposits in the United States.
21:39Vehicles called Vibrosis Trucks map the area, looking for underground oil deposits.
21:44At regular intervals, the trucks deliver a mechanized tremor of 25 tons of force down into the Earth.
21:54When the seismic wave rebounds, these earthquake generators systematically map the size, depth, and contour of geologic structures beneath the surface.
22:08Information that determines the probability a given location will yield oil.
22:24When the Vibrosis Trucks first gathered the data and created an oil well map in 1990,
22:30the oil-rich areas below the surface outline the contours of an impact crater eight miles in diameter.
22:37The impact created a geological anomaly, producing a mineral resource where it would not normally be found.
22:45And it's not just oil.
22:50Impact craters around the world are the cradles of some of the richest deposits of minerals and natural resources on Earth.
22:59The Vertifort Crater in South Africa has produced 40% of the gold found on the planet.
23:14The Sudbury Mine in Canada generates nickel, copper, and nickel sulfide ores.
23:20The Carswell Crater, also in Canada, is a uranium mine.
23:25The Rees Crater in Germany produces coal.
23:28The Papagai Crater in Russia is one of the world's richest sources of diamonds.
23:33Yes, impacts have a direct control over sort of human civilization.
23:38Dr. Richard Grieve of the Canadian Geological Survey has mapped most of the known impact craters on the Earth.
23:46He says one-third of the known craters harbor some sort of natural resource humans associate with economic value.
23:53Some of them are major reservoirs, some of them produce spring waters.
23:58They're quite important economically.
24:00The craters may have helped human civilization sort of rise.
24:04Ultimately, we're only around until the next big impact, and then human civilization is gone.
24:08So they have complete control over our lives.
24:13What eluded scientists was exactly how the comet impacts created life on Earth.
24:17But then a cask of wine provided the clue.
24:32While working with the French wine industry in 1848, scientist and doctor Louis Pasteur made a curious discovery.
24:53As wine ages in these massive wooden casks, a blackish-purple substance grows on the back of the barrels.
25:12This material is a mass clumping of wine crystals, a byproduct of wine fermentation Pasteur called wine diamonds, known more commonly today as tartaric acid.
25:25When Pasteur studied the wine diamonds under a microscope, he discovered the crystals came in only one shape.
25:33But artificial crystals he created in his lab had two shapes.
25:41One was identical to the natural tartaric acid crystal, and the other was its mirror image.
25:47The two forms were similar but different, much like left-handed and right-handed mittens.
25:53Because of this, Pasteur termed them left-handed and right-handed crystals.
25:58The two synthetic crystal molecules look almost identical, but in fact are impossible to superimpose.
26:08Just as it is impossible to put a right hand into a left-handed mitten.
26:20Since the natural wine diamond consisted of only left-handed crystals, Pasteur concluded that molecules associated with life are structured exclusively with a left-handed design.
26:30Today, we know the cells of living organisms, from blood cells to bone cells, consist of biological chemicals called proteins.
26:43A protein is made up of 20 different types of amino acids.
26:48Since nearly all living organisms on Earth, from bacteria to humans, make proteins only from left-handed amino acids,
27:01left-handed amino acids are the building blocks of life as we know it.
27:07When the Murchison meteorites smashed into the interior of Australia in 1969, evidence was found that life-forming left-handed amino acids may have originated in deep space.
27:24The drive was just really the recognition that the meteorites might provide us the opportunity to throw some light on a really fundamental question.
27:34Arizona State University organic chemist Dr. John Cronin and his colleague Dr. Sandra Pizzarello realized that finding amino acids within the Murchison meteorite would point to a relationship between life on Earth and life in deep space.
27:51If the organic compounds on the primitive Earth came from outside the Earth, if they were delivered to the Earth by meteorite or dust or cometary infall,
28:03then this organic matter would have already had the beginnings of this excess of one-handed forms over the other, as we see in the amino acids.
28:12From deep within the meteorite, Cronin and Pizzarello extracted amino acids not found on Earth, amino acids that were predominantly left-handed, the kind that could give a kickstart to life.
28:29What we find in the meteorite is that there are small excesses of one-handed form of amino acids over the other.
28:39In other words, there is the beginnings of a selection process represented in this material which was brought to the Earth from outside the Earth sources,
28:49like cometary or a small body or dust, in fall, a small excess of one form of the amino acid over the other, which could presumably have been amplified and bring us to a situation much nearer to what we find in life today.
29:06This discovery points to the idea that Earth's life forms originated not here, but somewhere else in the universe.
29:36And the same cosmic processes that may have helped life arise on Earth could also be seeding life elsewhere in the universe.
29:56The journey of discovery begins with mathematician and astronomer Galileo Galilei.
30:02In the early 1600s, Galileo searched the Italian night sky around the planet Jupiter, recording what he saw in his handwritten notebooks.
30:17The circle at the center is Jupiter, orbited by four moons indicated by asterisks.
30:24Galileo's discovery of Jupiter's orbiting moons led the astronomer to believe in the Copernician theory
30:30that everything in the universe does not revolve around the Earth.
30:35For his efforts, the Roman Catholic Church branded Galileo a heretic, relegating him to a life lived under house arrest.
30:47But Galileo fueled the idea that if Earth was not the center of the universe, perhaps other planets harbored life as well.
30:55To have life, you must have water.
31:00Seventy percent of Earth is covered with water.
31:13It is an absolute necessity for each of the nearly 30 million species to survive and thrive here.
31:19So astrobiologists have focused their search for planets in our galaxy where water might exist.
31:23The best possibility, Europa.
31:24One of the four moons of Jupiter discovered by Galileo.
31:25One of the four moons of Jupiter discovered by Galileo.
31:53Four hundred years after Galileo's discovery, the United States sent a space probe named after Galileo to explore Jupiter's moons.
32:07The images the Galileo probe transmitted back to Earth revealed Europa is covered with a layer of ice,
32:15presenting the possibility of a huge ocean, water, lying below.
32:23The probe's photographs captured these scar-like formations all over Europa's surface.
32:29These fractures, called double ridges, look very similar to cracks in the ice covering Antarctica.
32:36Okay, well let's talk a little bit about these ridges, guys.
32:38Dr. Richard Greenberg of the University of Arizona realized these double ridged cracks could only be made with the help of an ocean hidden below.
32:51As Jupiter exerts a massive tidal force on Europa, it pulls apart the surface ice and creates a colossal crack.
32:59As Europa gets closer to Jupiter and further away every three and a half days during its orbit, the shape of Europa changes.
33:07It gets longer and then shorter, longer and shorter.
33:10Naturally, this stresses the surface and it creates cracks.
33:13Once you have one of these cracks, the tides continue to work the crack.
33:18So you'll have a crack in the ice and the tides will cause the crack to open and close every day on Europa, every three and a half days on Earth.
33:25This break in the miles thick ice allows the water below to gush up.
33:35As soon as the water is exposed to the sub-freezing temperature on Europa's surface, it skims over with ice and slush.
33:43The crack then closes as Jupiter's periodic tidal force subsides.
33:49This squeezes fresh ice to the surface along the crack.
33:52When the crack opens again a few hours later, the new ice remains piled on each side.
34:00As the process repeats day after day, it builds a double ridge of ice piled along each side of the crack.
34:07Europa is about the same size as the Earth's moon.
34:13It is bombarded by radiation and so far from the sun, the surface temperature reaches 260 degrees Fahrenheit below zero.
34:21The ocean, however, may only be a few miles below the icy surface.
34:36And they'll frigid, a potential wellspring of alien plants and animals.
34:52So you might imagine plants growing in that zone where they're deep enough to be safe from radiation, but close enough to the surface that the sun can give them energy.
35:16Now, remember what makes the ridges.
35:20What makes the ridges is this crack opens and closes every day.
35:23And so water comes up and gets squeezed to the top, making ridges.
35:27Well, as the water goes up and some of the water goes down every day, this region is bathed by warm water coming up and going down, mixing oxidants and fuels and the chemicals below.
35:40This is just the sorts of conditions that life needs.
35:44There's a disequilibrium chemistry, you've got warmth, you've got a flow.
35:49So you can imagine organisms taking advantage of the setting.
35:53NASA astronomer Richard Terrell wants to find them.
35:59The main objective is to confirm the existence of liquid water ocean beneath the surface of Europa.
36:05It's also to go there and to understand the surface processes and to look for potential areas where the surface is young and potential places where we could land a lander in the future.
36:17The tremendous excitement with going to Europa is the potential of a biological environment.
36:23Here's a world five times further away from the sun than the earth is, which has an ocean of liquid water.
36:32And it opens up our thinking to further biological environments.
36:37Energy, liquid water and organic materials on earth, those same ingredients gave rise to life in less than a billion years.
36:45Well, that same organic soup has been cooking on Europa for four and half billion years.
36:51So potentially, Europa is a very, very exciting biological target.
36:55Does this mean there really are things living there?
36:59Well, we don't know.
37:01But biologists who are studying the extreme environments that things live in on earth are saying more and more that if you have a habitable environment, then things are there.
37:13The answer will hopefully come in the next decade, when NASA hopes to send another mission to Europa to land on its icy crust.
37:22The Europa Orbiter is going to be the most difficult mission ever undertaken.
37:26And the reason is, first, Jupiter is very far away, half a billion miles from the earth.
37:31Secondly...