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Astronomers have theorized that long-ago asteroid impacts delivered much of the water now filling Earth's oceans, as shown in this artist's conception. If true, the stirring provided by migrating planets may have been essential to bringing those asteroids.

In this artist's conception, Jupiter's migration through the solar system has swept asteroids out of stable orbits, sending them careening into one another. As the gas giant planets migrated, they stirred the contents of the solar system. Objects from as close to the Sun as Mercury, and as far out as Neptune, all collected in the main asteroid belt, leading to the diverse composition we see today.