From ammonia leaks to Space Shuttle disasters to a spacewalk gone terribly wrong, astronauts and Mission Control insiders relive the most terrifying moments during construction of the International Space Station.

From ammonia leaks to Space Shuttle disasters to a spacewalk gone terribly wrong, astronauts and Mission Control insiders relive the most terrifying moments during construction of the International Space Station.

Witness life-or-death decisions 250 miles above Earth, as astronauts and Mission Control work together to survive moments of high danger on board humanity's remarkable orbiting laboratory, the International Space Station.

Witness life-or-death decisions 250 miles above Earth, as astronauts and Mission Control work together to survive moments of high danger on board humanity's remarkable orbiting laboratory, the International Space Station.

Witness life-or-death decisions 250 miles above Earth, as astronauts and Mission Control work together to survive moments of high danger on board humanity's remarkable orbiting laboratory, the International Space Station.

Witness life-or-death decisions 250 miles above Earth, as astronauts and Mission Control work together to survive moments of high danger on board humanity's remarkable orbiting laboratory, the International Space Station.

In April 1775, war breaks out in Britain's most troublesome territory. Now the American Colonial Army faces what seems like an impossible challenge - to militarily defeat the world's most powerful nation. We've all heard the stories of pluck and valor, but what really led to Britain's defeat and the birth of the United States? American and British archeologists and historians unpack the real story of technology, innovation, and luck that determined the outcome of key battles - from the Massachusetts militias who fired the first shots to the Naval clashes between British and American ships of the line. This unique film brings the latest science to bear to reveal the hidden history of the Revolutionary War.

In April 1775, war breaks out in Britain's most troublesome territory. Now the American Colonial Army faces what seems like an impossible challenge - to militarily defeat the world's most powerful nation. We've all heard the stories of pluck and valor, but what really led to Britain's defeat and the birth of the United States? American and British archeologists and historians unpack the real story of technology, innovation, and luck that determined the outcome of key battles - from the Massachusetts militias who fired the first shots to the Naval clashes between British and American ships of the line. This unique film brings the latest science to bear to reveal the hidden history of the Revolutionary War.

For decades, scientists have tried to unlock the secrets of ancient DNA. Follow the dramatic quest to recover DNA millions of years old and reveal a lost world from before the last Ice Age.

For decades, scientists have tried to unlock the secrets of ancient DNA. Follow the dramatic quest to recover DNA millions of years old and reveal a lost world from before the last Ice Age.

Following a trail of fossils found in all the wrong places -- beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic -- uncover the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life.

Following a trail of fossils found in all the wrong places -- beech trees in Antarctica, redwoods and hippo-like mammals in the Arctic -- uncover the bizarre history of the poles, from miles-thick ice sheets to warm polar forests teeming with life.

Scientists investigate colossal explosions in Siberia and other evidence that rapidly melting soil in the Arctic is releasing vast amounts of methane, a potent greenhouse gas. What are the implications for our climate future?

After decades in the shadows, UFOs are being studied seriously. Are they weather balloons, optical illusions, secret military technology? Or something else? Follow scientists as they try to unravel the mystery of the strangest objects in our skies.

It's hard to imagine that large meteorites colliding with Earth with the power of 20 Hiroshima bombs can bring anything but cataclysm. Ever since a link was made between meteorite impacts and mass extinctions on Earth, we have feared rogue asteroids destroying our planet. There is no doubt, these objects can be takers of life - but is it possible that giant asteroid impacts were actually essential for the creation of life on Earth NOVA follows a series of discoveries behind a remarkable theory of how the violent destroyers of life could also have created the very special conditions - of chemistry and energy - that made life possible in the first place.