From the Physics arXiv blog:
Should we be more worried about Earth-impacting comets than asteroids?
The three largest impact craters on Earth are Vredefort (250km across), Sudbury (200 km across) and Chicxulub (170km). Most astronomers assume that these were created by asteroids roughly 10 kilometers across. But what of the possibility that comets may have been responsible one or more of these impacts?
Today David Minton and Renu Malhotra from the Lunar and Planetary Laboratory at the University of Arizona present some interesting calculations about the rate at which planet smashing asteroids are sent our way.
Contrary to the conventional view, the asteroid belt is a vibrant, dynamic region of the solar system with a complex structure. This is the result of the gravitational interaction of the major planets. This sets up orbital resonances which, over billions of years, have scoured the belt clean in various places. The famous Kirkwood gaps are one result of this process....MORE
- ...Biblical apocalypse. Hey, over 1 billion people on the planet believe this could happen so we have to take it seriously. News Corp (NWS Quote), which owns the largest bible publisher, Zondervan, would benefit....