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About 4.56 billion years agoPeer-reviewed · 2 sourcesWell documented

The giant planets take shape and carve the asteroid belt

On the timeline · around About 4.56 billion years ago · Building the PlanetsNebula and SunBuilding the PlanetsThe giant planets take shape and carve the asteroid belt4.6 Ga4.6 Ga4.6 Ga4.6 Ga4.6 Ga4.5 Ga

What happened

Beyond the frost line, where ice joined rock and metal as building material, Jupiter and Saturn grew far faster and larger than the inner worlds and drew in thick envelopes of gas to become the giant planets. Their gravity then reshaped everything closer in. NASA credits the young Jupiter's pull with ending planet formation in the gap between Mars and Jupiter, stirring the bodies there so hard that they shattered in collisions instead of merging, and that stranded rubble is the asteroid belt. A 2023 study in Scientific Reports models how a near-resonant Jupiter and Saturn set off chaotic gravitational stirring that emptied the disk beyond about 1 to 1.5 times the Earth-Sun distance over some 5 to 10 million years.

Why it matters

The giants set the boundary conditions for the rocky planets. The same stirring that emptied the asteroid belt is a leading explanation for why Mars is only about a tenth of Earth's mass, and it limited how much material Earth itself could gather.

How we know

The asteroid belt is the standing evidence: a zone of rocky bodies between Mars and Jupiter that never became a planet, which NASA attributes to Jupiter's gravity. The Scientific Reports model reproduces both that emptied belt and Mars's small mass from Jupiter and Saturn's early orbits, without the more extreme migration some rival models require.

Sources

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Part of a timelineThe Formation of the Solar System11 events · The 800 million years that turned a collapsing cloud of gas into the Sun, the planets, and a habitable Earth, from the oldest solids we can date to the first oceans.View all →
The giant planets take shape and carve the asteroid belt · The Formation of the Solar System · SourcedStory