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Jupiter may have acted like a giant wrecking ball in the newborn solar system, roaming in to destroy an early generation of inner planets before retreating to its current orbit, researchers say.
The typical planetary system is made up of a few super-Earths — rocky planets up to 10 times the mass of Earth — orbiting much closer to their stars than Mercury does the sun. Moreover, planetary systems that possess giant planets similar to Jupiter and Saturn typically have them much closer to their stars than in the solar system.
"Our solar system is looking increasingly like an oddball," study co-author Gregory Laughlin, an astronomer at the University of California, Santa Cruz, said in a statement.
The researchers modeled a leading scenario for the formation of Jupiter and Saturn known as the "Grand Tack," wherein Jupiter arose first and migrated toward the sun until Saturn formed, which caused Jupiter to reverse course and migrate outward to its current orbit. They calculated what might happen if a set of rocky planets formed in the inner solar system before Jupiter migrated inward.
As Jupiter moved inward, its gravitational pull would have slung these nascent inner worlds into close-knit, overlapping orbits. This would have set off a series of collisions that smashed these newborn worlds into pieces.
A second generation of inner planets would have formed later from the depleted material that was left behind. This would explain why Mercury, Venus, Earth and Mars are younger than the outer planets, and why they are both smaller and have much thinner atmospheres than inner worlds seen in other planetary systems.
One implication of these findings is that life as it is known on Earth might be rarer in the universe than previously thought.
Lead study author Konstantin Batygin, a planetary scientist at the California Institute of Technology in Pasadena, told Space.com: "Extrasolar life, where it exists, will differ substantially from our common definition and thrive in its own unique environment that is unlike anything we are used to."
Batygin and Laughlin detailed their findings online Monday in the journal Proceedings of the National Academy of Sciences.