Geoscience Reference
In-Depth Information
the asteroids. Mars might then have absorbed many more planetesimals and grown
as large as the Earth. Theia might have struck Mars instead of Earth.
The early solar system was like a cosmic pinball machine, all of whose balls
were let fly at once, colliding and rebounding off posts, bumpers, and one another
at random until at last they all settled down. Shoot all the balls again, and a dif-
ferent set of events would be bound to occur. Run the history of the solar system
again, and without the slightest doubt, our species would not exist. We are here
only because of a myriad succession of random events. Our existence owes not to
destiny or divine creation but to the chance impact of a meteorite, a process that
scientists did not recognize until the 1960s.
