In a key geological moment about 66 million years ago, an enigmatic something killed off almost all the dinosaurs and some 70 percent of all other species living on Earth.
Scientists say they're homing in on the precise date of both the extinction of the dinosaurs 66 million years ago, and the massive impact that's believed by many to have caused it.
To the surprise and delight of astronomers, a comet discovered just two weeks ago as it hurtled towards the sun has skimmed the star and re-emerged the other side.
Astronomers have come up with two competing theories to explain a mysterious cosmic explosion first detected by NASA's Swift observatory on Christmas Day 2010.
Earth's oceans could once have been giant icebergs floating through space, an ESA team has concluded, after examining the isotopic composition of a comet.
The Stardust spacecraft's Valentine's Day flyby of the Tempel 1 comet has delivered pictures of the comet that clearly show the effects of its last encounter with a spacecraft in 2005.
Rather appropriately for the time of year, NASA's EPOXI team says that the mission's recent encounter with comet Hartley 2 observed a flurry of snow streaming out from the comet.
