A possible spike in the number of impacts in the inner solar system about 4 billion years ago may have mostly likely been due to

Question

Quizplus · Accepted Answer

Planetary migration caused by the shifting of the orbits of the Jovian planets is the most likely reason for a spike in impacts in the inner solar system about 4 billion years ago. As the Jovian planets (Jupiter, Saturn, Uranus, and Neptune) migrated to their current positions, their gravitational influence on smaller objects in the solar system caused them to be flung outward, some of which migrated into the inner solar system and collided with other objects, causing a spike in impacts. Other options like the passage of another star close to the Sun, the giant collision that formed the Moon or the breakup of a planet to form the asteroid belt can not explain the spike in impacts in the inner solar system about 4 billion years ago as they happened much earlier or later than that time frame.

A Possible Spike in the Number of Impacts in the Inner