Jupiter destroyed ‘super-Earths’ in our early solar system
NASA/JPL/University of Arizona

Jupiter destroyed 'super-Earths' in our early solar system

Lucky us: If Jupiter and Saturn hadn’t formed where they did—and at the sizes they did—as the disk of dust and gas around our sun coalesced, then our solar system would be a very different and possibly more hostile place, new research suggests. More than half of the sunlike stars in our galactic neighborhood have so-called super-Earths (planets with masses between one and 10 times that of ours) orbiting them more than once every 100 days or so, which roughly places those orbs at a distance of Mercury or less from their parent stars. But only about 10% have planets the size of Jupiter or Saturn, scientists note. Previously, computer simulations have described how Jupiter and Saturn migrated inward and then retreated from the sun to their current positions as our solar system formed. Now, similarly detailed models that tracked the fate of thousands of objects closer to our nascent sun reveal what effects those peregrinations had on material in the inner solar system. In the solar system’s first 3 million years or so, gravitational interactions with Jupiter, Saturn, and the gas in the protoplanetary disk would have driven any super-Earth–sized planets closer to the sun and into increasingly elliptical orbits, the simulations suggest. In such paths, a cascade of collisions would have blasted any orbs present there into ever smaller bits, which in turn would have been slowed by the interplanetary equivalent of atmospheric drag and eventually plunged into the sun, the researchers report online this week in the Proceedings of the National Academy of Sciences. As Jupiter retreated from its closest approach to the sun (about the distance of Mars’s orbit today), it left behind the mostly rocky remnants that later coalesced into our solar system’s inner planets, including Earth. Besides explaining the estimated differences in ages between gas giants such as Neptune and Uranus and rocky worlds such as Earth and Venus, the new findings help explain how gas-swaddled super-Earths—ones possibly shrouded with inhospitable atmospheres—were banished from an otherwise inhabitable neighborhood.