"The extinction of the dinosaurs 65 million years ago can be traced to a collision between two monster rocks in the asteroid belt nearly 100 million years earlier, scientists report on Wednesday.
The smash drove a giant sliver of rock into Earth's path, eventually causing the climate-changing impact that ended the reign of the dinosaurs and enabled the rise of mammals — including, eventually, us.
Other asteroid fragments smashed into the Moon, Venus and Mars, pocking their faces with mighty craters, the researchers believe. Mixing skills in time travel, jigsaw-making and carbon chemistry, the trio carried out a computer simulation of the jostling among orbital rubble left from the building of the Solar System.
The sleuths were guided by an intriguing clue — a large asteroid called Baptistina, which shares the same orbital track as a group of smaller rocks.
Turning the clock back, the simulation found that the Baptistina bits not only fit together, they were also remnants of a giant parent asteroid, around 105 miles across, that once cruised the innermost region of the asteroid belt.
Around 160 million years ago — the best bet in a range of 140-190 million years — this behemoth was whacked by another giant some 37 miles across.
From this soundless collision was born a huge cluster of rocks, including 300 bodies larger than six miles and 140,000 bodies larger than 0.6 of a mile." Courtesy of Discovery Space Channel.