NASA's Unexplained Files Season 4 Episodes
Season 4 Episode Guide
Episode 1 - Pluto's Stranger ThingsAstronomers find evidence for incredible alien technology around a distant star. The first pictures of Pluto show that something might be moving across its surface. Apollo astronauts see something they can't explain as they approach the moon.
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Episode 2 - Rise of the Planet KillerA mission to Mars captures an image of a strange structure on the Red Planet. Files from the first Apollo mission record an eerie sighting on the dark side of the moon. A planet-eating star gives scientists a glimpse of Earth's terrible demise.
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Episode 3 - A President's Close EncounterGeysers are discovered on a frozen moon, and NASA redirects a probe on a daring mission to detect evidence of life. An unidentified object is spotted approaching a near-earth asteroid. A future US President is an eyewitness to a UFO.
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Episode 4 - The Earth Next DoorAstronomers detect a potentially habitable planet tantalizingly close to Earth. A chance discovery at NASA reveals a top secret military space program. The Apollo missions bring back evidence that the moon could be rich in the building blocks for life.
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Episode 5 - Curse of the Full MoonTwo cosmonauts fight for their lives while trapped inside a capsule in a frozen lake. A NASA scientist investigates the deadly Nazi secret that doomed the Hindenburg. NASA astronomers are spooked when the full moon starts affecting their experiments.
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Episode 6 - Did Earth Have Two Moons?A startling discovery suggests that the hellish clouds of Venus may be the origin of life on Earth. A bizarre sighting 2,000 years ago raises the possibility that the Earth once had two moons. A NASA scientist helps the FBI crack the 1996 Olympic bombing.
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Episode 7 - Mystery of the Invisible PlanetA probe carrying a message to aliens mysteriously malfunctions as it enters deep space. A NASA mission goes disastrously wrong when an imposter breaches Mission Control. Astronomers find evidence of an invisible planet in a distant solar system.
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Episode 8 - Mars's Deepest SecretBritish astronomers working for the CIA intercept Soviet photos of the moon. A malfunction on the ISS could poison its crew with deadly ammonia gas. A startling image taken by a NASA probe points to evidence that life could exist on Mars.
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