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 and an unidentified object in Earth orbit stalks Russian spacecraft.

Apollo 12 astronauts bring back something alive from the moon and NASA tracks 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.

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, and a Soyuz capsule carrying NASA astronaut Peggy Whitson back to Earth vanishes without explanation.

Three cosmonauts die mysteriously as they re-enter Earth's atmosphere, a declassified document reveals a CIA plan to use a space disaster as a cover to start World War III 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.

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 explain a void at the edge of the solar system.