English: Computer generated gravity map image of the Chixulub Crater in Mexico.

Original caption

This is a computer-generated gravity map image of the Chicxulub Crater found on Mexico's Yucatan Peninsula. The buried impact structure has been implicated in the mass extinction of life 65 million years ago and may be much larger than scientists first suspected.

New analyses of gravity measurements in the region have turned up evidence that the feature is a multiring basin with a fourth, outer ring about 300 kilometers in diameter. At this diameter, the Chixulub Basin represents one of the largest collisions in the inner solar system since the so-called "heavy bombardment" ended almost four billion years ago. (The period of heavy bombardment was caused by the impact of debris from the early formation of the solar system raining in on the newly formed planets.) The only comparable post-bombardment basin is the 280-kilometer-diameter Mead Basin on Venus.