On Wednesday, September 29, the Earth came within one million miles of the asteroid Toutatis -- the closest predicted aproach of our fair planet to a sizable asteroid or comet in this century. Coming within...

On November 29, 1996 the Earth came within 3.3 million miles of the asteroid Toutatis. Above is a computer simulated picture of this spectacle from the surface of Toutatis (a 2.5 degree field of view looking toward Earth). In Earth's sky, Toutatis appeared only as a faint object moving against a background of stars.

Could humans live beneath the surface of the Moon? This intriguing possibility was bolstered in 2009 when Japan's Moon-orbiting SELENE spacecraft imaged a curious hole beneath the Marius Hills region on the Moon, possibly a skylight to an underground lava tube.