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  • Our world, warm, comfortable, familiar...

  • ...but when we look up, we wonder:

  • Do we occupy a special place in the cosmos?

  • Or are we merely a celestial footnote?

  • Is the universe welcoming or hostile?

  • We could stand here forever, wondering.

  • Or we could leave home, on the ultimate adventure.

  • To discover wonders.

  • Confront horrors.

  • Beautiful new worlds.

  • Malevolent dark forces.

  • The beginning of time.

  • The moment of creation.

  • Would we have the courage to see it through?

  • Or would we run for home?

  • There's only one way to find out.

  • Our journey through time and space begins with a single step.

  • At the edge of space, only 6O miles up...

  • ...just an hour's drive from home.

  • Down there, life continues.

  • The traffic is awful, stocks go on trading...

  • ...and Star Trek is still showing.

  • When we return home, if we return home...

  • ...will it be the same?

  • Will we be the same?

  • We have to leave all this behind.

  • To dip our toes into the vast dark ocean.

  • On to the Moon.

  • Dozens of astronauts have come this way before us.

  • Twelve walked on the Moon itself.

  • Just a quarter of a million miles from home.

  • Three days by spacecraft.

  • Barren.

  • Desolate.

  • It's like a deserted battlefield.

  • But oddly familiar.

  • So close, we've barely left home.

  • Neil Armstrong's first footprints.

  • Looks like they were made yesterday.

  • There's no air to change them.

  • They could survive for millions of years.

  • Maybe longer than us.

  • Our time is limited.

  • We need to take our own giant leap.

  • One million miles, 5 million, 2O million miles.

  • We're far beyond where any human has ever ventured.

  • Out of the darkness, a friendly face.

  • The goddess of love, Venus.

  • The morning star.

  • The evening star.

  • She can welcome the new day in the east...

  • ...say good night in the west.

  • A sister to our planet...

  • ...she's about the same size and gravity as Earth.

  • We should be safe here.

  • But the Venus Express space probe is setting off alarms.

  • It's telling us, these dazzling clouds, they're made of deadly sulfuric acid.

  • The atmosphere is choking with carbon dioxide.

  • Never expected this. Venus is one angry goddess.

  • The air is noxious, the pressure unbearable.

  • And it's hot, approaching 900 degrees.

  • Stick around and we'd be corroded, suffocated, crushed and baked.

  • Nothing can survive here.

  • Not even this Soviet robotic probe.

  • Its heavy armor's been trashed by the extreme atmosphere.

  • So lovely from Earth, up close, this goddess is hideous.

  • She's the sister from hell.

  • Pockmarked by thousands of volcanoes.

  • All that carbon dioxide is trapping the Sun's heat.

  • Venus is burning up.

  • It's global warming gone wild.

  • Before it took hold, maybe Venus was beautiful, calm...

  • ...more like her sister planet, Earth.

  • So this could be Earth's future.

  • Where are the twinkling stars?

  • The beautiful spheres gliding through space?

  • Maybe we shouldn't be out here, maybe we should turn back.

  • But there's something about the Sun, something hypnotic, like the Medusa.

  • Too terrible to look at, too powerful to resist.

  • Luring us onwards on, like a moth to a flame.

  • Wait, there's something else, obscured by the Sun.

  • It must be Mercury.

  • Get too close to the Sun, this is what happens.

  • Temperatures swing wildly here.

  • At night, it's minus 275 degrees...

  • ...come midday, it's 800 plus.

  • Burnt then frozen.

  • The MESSENGER space probe is telling us something strange.

  • For its size, Mercury has a powerful gravitational pull.

  • It's a huge ball of iron, covered with a thin veneer of rock.

  • The core of what was once a much larger planet.

  • So where's the rest of it?

  • Maybe a stray planet slammed into Mercury...

  • ...blasting away its outer layers in a deadly game of cosmic pinball.

  • Whole worlds on the loose careening wildly across the cosmos...

  • ...destroying anything in their path.

  • And we're in the middle of it.

  • Vulnerable, exposed, small.

  • Everything is telling us to turn back.

  • But who could defy this?

  • The Sun in all its mesmerizing splendor.

  • Our light, our lives...

  • ...everything we do is controlled by the Sun.

  • Depends on it.

  • It's the Greek god Helios driving his chariot across the sky.

  • The Egyptian god Ra reborn every day.

  • The summer solstice sun rising at Stonehenge.

  • For millions of years...

  • ...this was as close as it got to staring into the face of God.

  • It's so far away...

  • ...if it burned out, we wouldn't know about it for eight minutes.

  • It's so big, you could fit one million Earths inside it.

  • But who needs numbers? We've got the real thing.

  • We see it every day, a familiar face in our sky.

  • Now, up close, it's unrecognizable.

  • A turbulent sea of incandescent gas.

  • The thermometer pushes 10,000 degrees.

  • Can't imagine how hot the core is, could be tens of millions of degrees.

  • Hot enough to transform millions of tons of matter...

  • ...into energy every second.

  • More than all the energy ever made by mankind.

  • Dwarfing the power of all the nuclear weapons on Earth.

  • Back home, we use this energy for light and heat.

  • But up close, there's nothing comforting about the Sun.

  • Its electrical and magnetic forces erupt in giant molten gas loops.

  • Some are larger than a dozen Earths.

  • More powerful than 10 million volcanoes.

  • And when they burst through, they expose cooler layers below...

  • ...making sunspots.

  • A fraction cooler than their surroundings, sunspots look black...

  • ...but they're hotter than anything on Earth.

  • And massive, up to 2O times the size of Earth.

  • But one day, all this will stop.

  • The Sun's fuel will be spent.

  • And when it dies, the Earth will follow.

  • This god creates life, destroys it...

  • ...and demands we keep our distance.

  • This comet strayed too close.

  • The Sun's heat is boiling it away...

  • ...creating a tail that stretches for millions of miles.

  • It's freezing in here.

  • There's no doubt where this comet's from, the icy wastes of deep space.

  • But all this steam and geysers and dust...

  • ...it's the Sun again, melting the comet's frozen heart.

  • Strange.

  • A kind of vast, dirty snowball, covered in grimy tar.

  • Tiny grains of what looks like organic material...

  • ...preserved on ice, since who knows when...

  • ...maybe even the beginning of the solar system.

  • Say a comet like this crashed into the young Earth billions of years ago.

  • Maybe it delivered organic material and water...

  • ...the raw ingredients of life.

  • It may even have sown the seeds of life on Earth...

  • ...that evolved into you and me.

  • But say it crashed into the Earth now.

  • Think of the dinosaurs, wiped out by a comet or asteroid strike.

  • It's only a question of time.

  • Eventually, one day, we'll go the way of the dinosaurs.

  • If life on Earth was wiped out, we'd be stuck out here...

  • ...homeless, adrift in a hostile universe.

  • We'd need to find another home.

  • Among the millions, billions of planets...

  • ...there must be one that's not too hot, not too cold, with air, sunlight, water...

  • ...where, like Goldilocks, we could comfortably live.

  • The red planet.

  • Unmistakably Mars.

  • For centuries, we've looked to Mars for company...

  • ...for signs of life.

  • Could there be extraterrestrial life here?

  • Are we ready to rewrite the history books, to tear up the science books...

  • ...to turn our world upside down?

  • What happens next could change everything.

  • Mars is the planet that most captures our imagination.

  • Think of B-movies, sci-fi comics, what follows?

  • Martians?

  • It's all just fiction, right?

  • But what if there really is something here?

  • Hard to imagine, though. Up close, this is a dead planet.

  • The activity that makes the Earth livable shut down millions of years ago here.

  • Red and dead.

  • Mars is a giant fossil.

  • Wait. Something is alive.

  • A dust devil, a big one.

  • Bigger than the biggest twisters back home.

  • There's wind here.

  • And where there's wind, there's air.

  • Could that air sustain extraterrestrial life?

  • It's too thin for us to breathe.

  • And there's no ozone layer.

  • Nothing to protect us against the Sun's ultraviolet rays.

  • There is water...

  • ...but frigid temperatures keep it in a constant deep freeze.

  • It's hard to believe anything could live here.

  • Back on Earth, there are creatures that survive in extreme cold, heat...

  • ...even in the deepest ocean trenches.

  • It's as though life is a virus.

  • It adapts, spreads.

  • Maybe that's what we're doing right now...

  • ...carrying the virus of life across the universe.

  • Even in the most extreme conditions, life usually finds a way.

  • But on a dead planet?

  • With no way to replenish its soil, no heat to melt its frozen water?

  • All this dust, it's hard to see where we're going.

  • Olympus Mons, named after the home of the Greek gods.

  • A vast ancient volcano.

  • Three times higher than Everest.

  • There's no sign of activity.

  • Since its discovery in the 1970s, it's been declared extinct.

  • Hang on.

  • These look like lava flows.

  • But any sign of lava should be long gone, obliterated by meteorite craters.

  • Unless, this monster isn't dead, just sleeping.

  • There could be magma flowing beneath the crust right now...

  • ...building up, waiting to be unleashed.

  • Volcanic activity could be melting frozen water in the soil...

  • ...pumping gases into the atmosphere, recycling minerals and nutrients.

  • Creating all the conditions needed for life.

  • This makes the Grand Canyon look like a crack in the sidewalk.

  • Endless desolation...

  • ...so vast it would stretch all the way across North America.

  • But here, signs of activity, erosion, and what looks like dried up river beds.

  • Maybe volcanic activity melted ice in the soil...

  • ...sending water gushing through this canyon.

  • Underground volcanoes could still be melting ice, creating water.

  • And where there's water, there could be life.

  • The hunt for life is spearheaded by this humble fellow...

  • ...the NASA rover, Opportunity.

  • It's finding evidence that these barren plains...

  • ...were once ancient lakes or oceans that could have harbored life.

  • Look at those gullies.

  • Probes orbiting Mars keep spotting new ones.

  • More proof that Mars is alive and kicking...

  • ...that water is flowing beneath its surface right now.

  • Water that could be sustaining Martian life.

  • Now, all we have to do is find it.

  • Maybe we've already found what we're looking for on Earth.

  • Some think that life started here and then migrated to Earth.

  • An asteroid impact could've blasted fragments of Mars...

  • ...complete with tiny microbes out into space...

  • ...and onto the young Earth where they sowed the seeds of life.

  • No wonder we find Mars fascinating, this could be our ancestral home.

  • It could be we are all Martians.

  • The Mars we thought we knew is gone...

  • ...replaced by this new, active, changing planet.

  • And if we don't know Mars, our next door neighbor...

  • ...how can we even imagine what surprises lie ahead?

  • Our compass points across the cosmos...

  • ...back in time 14 billion years...

  • ...to the moment of creation.