NASA's Unexplained Files

The Viking Lander may have found life on Mars, but why don't we know about it? Plus, how could a starship be spotted in the Aurora Borealis?

A chunk of the sun appears to have vanished. Plus, the Hubble Space Telescope spots thousands of unidentified objects travelling faster than light. Are we being watched?

A distant planet shows evidence of an Earth-like atmosphere, while a mysterious glowing light on the Moon mystifies astronauts. Have they found evidence of a crashed alien ship?

Countless mysterious objects have been caught by NASA's cameras. We'll reveal NASA's top ten unexplained encounters using groundbreaking interviews with astronauts and scientists.

When astronaut Leroy Chao's high-risk spacewalk is interrupted by bright lights flying past, it sparks a major investigation. Could alien life forms be to blame?

A UFO crashes in Pennsylvania. Was it a secret Soviet satellite, or something far more dangerous? On Mercury, NASA finds the impossible: frozen water.

Images of Mercury reveal massive spider-like formations on its surface. Is it an odd geological formation - or something much more ominous?

The show returns with more mysterious encounters, unusual discoveries and strange sightings, straight from NASA's best and brightest.

What are the mysterious trails on the lunar surface near the Apollo landing sites? Does a strange space object spell disaster for the crew of the space shuttle?

Something in space is attacking the brains of our astronauts. What is it? Should NASA be worried about the sudden appearance of so-called space fireflies?

An astronaut on a spacewalk begins to drown. How could this alarming event happen? Plus, have NASA discovered an asteroid that's been converted into a spacecraft?

Could NASA really be responsible for a nuclear explosion on Jupiter? Could new evidence finally reveal the truth behind the mystery of the iconic face on Mars?

A Russian probe discovers something has disturbed the lunar soil before the US or the USSR got there. But did the Nazis get there first?

Two cosmonauts fight for their lives, trapped inside a capsule in a frozen lake. NASA astronomers are spooked when the full moon affects their experiments.

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?