A UFO crashes in Pennsylvania. Was it a secret Soviet satellite -- or something far more dangerous? On Mercury, NASA finds the impossible: frozen water. A strange object causes a skyscraper-sized shadow on the surface of Mars's largest moon. What is it?

Was the Moon landing faked? Images of Mercury reveal massive spider-like formations on its surface. Is it an odd geological formation -- or something much more ominous? A classifed space shuttle mission ends in near-disaster. What was its secret mission?

Are burning lights in the skies above Nevada and Utah signs of a secret space weapons project? 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 terrifying event happen? Have NASA scientists discovered an asteroid that's been converted into a spacecraft? What are the strange objects spotted when NASA sends a top-secret payload into space?

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? What unknown force crashed a spacecraft from the Apollo program into the lunar surface?

A Russian probe discovers something has disturbed the lunar soil before the US or the USSR got there. Did Nazis get there first? Have scientists detected a laser signal from a planet capable of supporting life? Is there really a Bermuda Triangle of Space?

How did pictures from the Hubble telescope make the comet of the century look like an alien spacecraft? Has earth already been invaded by alien organisms? What mysterious force is smashing a near-earth asteroid to pieces?

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? Who could be responsible for the bizarre glowing spiral in the skies over Norway?