GALLERY
Post-Lunar Cataclysm View of the Solar System
Approximately 400 million years after solar system formation, the orbits of Jupiter, Saturn, and the other giant planets moved. Jupiter moved slightly closer to the Sun while Saturn moved farther away. This caused a series of gravitational disturbances to ripple through the asteroid belt. That event dynamically excited or stirred up the asteroids, sending many of them into higher inclination and more elliptical orbits that pushed them into the inner solar system. That dramatic flux of near-Earth asteroids caused a much higher impact cratering rate on the Earth and Moon in what scientists often call the lunar cataclysm. Impact velocities appear to have doubled when the asteroids were stirred up, causing a shift in the crater size distribution that can be detected today in the most ancient of the lunar highlands. The shifting gravitational disturbances also led to the formation of gaps within the asteroid belt that are seen today. Image Credit: LPI\SwRI\CNRS