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