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An early maelstrom shaped our Solar System. Sometime after the planets took shape from primordial gas and dust, resonant tugs between the giant planets threw their orbits out of kilter. The gravity of the errant giants blasted Pluto and its many icy neighbors into the far-out Kuiper belt. The instability also scattered oddball moons and asteroids and triggered smaller bodies to pummel the inner planets.
Now, that scenario is experiencing some upheaval of its own.
Nesvorný - Scientist - Southwest - Research - Institute
Nesvorný, a planetary scientist at the Southwest Research Institute (SwRI) in Boulder, Colorado. Several new papers explore what triggered this early instability and how it can explain a host of Solar System quirks.
Two decades ago, scientists recognized that planets must have migrated to create the modern Solar System. A group including Alessandro Morbidelli, a planetary scientist at the University of Côte d’Azur, gathered in Nice, France, for 1 year to hash out the idea, creating what’s known as the Nice model. As the model now goes, after the giant planets formed out of the gas disk, Jupiter drew its fellow giants into a resonant chain of orbits where, for example, Saturn orbited the Sun three times for two turns of Jupiter. The surrounding gas acted as a damping agent, calming any instability like an air conditioner in a room of irritable siblings. But once the gas dissipated, the collective push and pull of giant planets’ masses, agitated by nearby planetary building blocks, unleashed chaos.
Turmoil - Lunar - Rocks - Impact - Craters
The turmoil came relatively late, suggested lunar rocks collected from impact craters by the Apollo astronauts. The ages of the rocks seemed to indicate that the Moon suffered a cataclysmic assault, dubbed the Late Heavy Bombardment (LHB), 3.95 billion years ago, sandwiched by hundreds of millions of years of quiet. But over the past few years this story has evaporated, says Nicolle Zellner, a...
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