What's Past Is Prologue

NASA, ESA, Leah Hustak (STScI) This artist’s concept depicts a Trans-Neptunian Object, a small, faint, icy body orbiting the Sun beyond the orbit of Neptune. The formation of our solar system was a complex process, but there are two things we know quite well. The first is that where a body forms has a significant effect on its composition. The icy giants of Neptune and Uranus formed at the outer region of the solar system, beyond the snow line. Earth and Venus formed close to the Sun, where solar winds stripped their atmospheres of hydrogen and helium. The second is that where a body forms isn’t where it necessarily stays. Jupiter and Saturn migrated inward as they formed. They were closer to the Sun until the Great Migration shifted them to their present orbits. This planetary realignment also triggered the Late Heavy Bombardment period about 4 billion years ago, when Earth experienced some of its largest impacts. It has been generally thought that planetary bodies maintain their…