NASA's Unexplained Files

A NASA spacecraft suffers a malfunction in orbit - can its lone astronaut make it back to Earth? Plus, new evidence emerges over Yuri Gagarin's mysterious death.

When the Soviet Union unveils its own space shuttle, the CIA hatches a revenge plot. Plus, a missing nuclear weapon could threaten a NASA base in the Arctic.

A NASA probe captures an image of a familiar structure on the surface of Mars. What made 'Mars Henge'? Plus, how did an Apollo astronaut get sick on the Moon?

Geologists discover alien deposits on the Earth's surface - and the answer could shed light on the cause of the greatest extinction in its history.

Witnesses photograph two suns in the sky over Indonesia - is this the first sighting of the Sun's dark twin that could spell imminent danger to Earth?

Jupiter is hotter than it should be, and scientists are baffled. There's a strange discovery on Mars and detectives ask for NASA's help on a murder cold case.

A malfunction on the ISS could poison its crew with a deadly gas. A startling image taken by a NASA probe points to evidence that life could exist on Mars.

A probe mysteriously malfunctions as it enters deep space. Astronomers find evidence of an invisible planet in a distant solar system.

A starling discovery suggests the hellish clouds of Venus may be the origin of life on Earth. Plus, did the earth once have two moons?

Newly discovered documents reveal NASA's secret plan B for failure of the first moon landing. And NASA's Cassini mission unravels a 300-year-old mystery.