Uranus, Neptune swapped spots, new model says

A new theory of planetary formation, proposed by ASU astrophysicist Steve Desch, challenges the established theory that the gas giants formed from planetary materials that moved inward toward the sun. Existing models have Uranus and Neptune taking billions of years to form. But chemical clues in their atmospheres mean that they didn't have that much time, says Desch, "It's important to form those planets within ten million years, because that's how long hydrogen and helium gas remain in the early solar system.” Article source: National Geographic