NASA's Unexplained Files

Lost tapes reveal that Apollo astronauts heard unexplained transmissions on the far side of the moon, an amateur astronomer spots a strange disturbance in Martian atmosphere and an unidentified object in Earth orbit starts stalking Russian spacecraft.

Apollo 12 astronauts bring back something alive from the moon and NASA track an asteroid heading towards Earth but make a shocking discovery: it's not an asteroid, but an object that's artificial in nature.

Neil Armstrong goes into an unexplained spin. He needs to figure out what's causing it, or he faces certain death. An Apollo 17 photo seems to show a US military outpost on the Moon... and could there be alien life swimming in the oceans of Jupiter's moons.

When a Chinese moon rover breaks down, a NASA scientist points to a mysterious material that seemed to sabotage the Apollo missions, decades earlier. The Rosetta spacecraft finds a comet that appears to be singing.

Recently discovered documents reveal NASA's secret plan B for failure of the first moon landing, a Soyuz capsule carrying NASA astronaut Peggy Whitson back to Earth vanishes without explanation and NASA's Cassini mission unravels a mystery.

Three cosmonauts die mysteriously as they re-enter Earth's atmosphere and NASA needs to know why, a declassified document reveals a CIA plan to use a space disaster as a cover to start World War 3 and a NASA rover discovers clues that help solve a murder.

Two astronauts trapped in the vacuum of space face an agonizing death; the first close up images of Pluto reveal an alien landscape, and residents of Houston struggle to explain videos of unidentified flying lights captured above their city at night.

Astronauts are evacuated when a mystery object is discovered hurtling towards the ISS, a NASA secret agent goes undercover to recover missing moon rocks and scientists struggle to find answers when they find a huge void at the edge of the solar system.

Strange sightings on Mars, including possible pillars of fire and signs of life.