NASA's Unexplained Files

Evidence of alien technology around a distant star; speculation about Pluto's surface; Apollo astronauts are at a loss of words to describe an object they encountered while they approached the moon. Science Channel has named this episode the first episode of season 4.

A mars mission captures an image of a strange structure on the planet; an intriguing sight on the dark side of the moon; a planet-eating star gives scientists a peek of Earth's bleak future.

The discovery of geysers on a moon; NASA's mission to detect life; an object is spotted approaching an asteroid.

Astronomers notice a planet in Earth's vicinity capable of supporting life; top secret military program exposed; the moon contains the components to start life.

Cosmonauts are trapped in a capsule in a frozen lake; a NASA scientist investigates the Hindenburg; the full moon affects experiments.

A discovery suggests the hellish clouds of Venus may be the origin of life on Earth. A bizarre sighting 2,000 years ago raises the possibility that Earth once had two moons. A scientist helps the FBI crack the 1996 Olympic bombing.

A probe carrying a message to aliens malfunctions as it enters deep space. A NASA mission goes disastrously wrong when an imposter breaches Mission Control. Astronomers may have found an invisible planet around a distant star.

Soviet photos of the moon are intercepted by the CIA; a malfunction aboard the ISS, which imperils the whole crew; NASA probe finds evidence of the possibility of life on Mars.