The asteroid belt reveals the drama of the solar system’s early evolution

A better understanding of the asteroid belt has revealed just how dynamic the solar system was in its early days, a new study reports.

Over the past decade, astronomers have realized that the main belt asteroids between Mars and Jupiter are incredibly diverse in size and composition. This diversity runs counter to earlier notions that space rocks all formed where they are now, implying instead that they were scattered here and there by migrating planets during the first billion years. years in the history of the solar system.

“In modern dynamical models, the giant planets are thought to have migrated substantial distances, shaking asteroids – which formed throughout the solar system – like flakes in a snow globe, and carrying some of them at their present location in the asteroid belt.” Francesca DeMeo and Benoit Carry, of the Harvard-Smithsonian Center for Astrophysics and the Paris Observatory, respectively, write in a study published online today (January 29). in the journal Nature. “The main asteroid belt thus samples conditions throughout the solar system.” [The Strangest Asteroids in the Solar System]

Most asteroids orbit the Sun in a wide belt located between the orbits of Mars and Jupiter: the asteroid belt. Get the facts about the asteroid belt in this infographic. (Image credit: contributor Karl Tate)

While the basic idea of ​​planetary migration has been around for some time, the effect of such movements on the asteroid belt has just begun to be appreciated over the last decade or so, DeMeo and Carry write in their paper. , which reviews recent advances in the discovery and characterization of the rocks of the belt.

In the 1980s, for example, astronomers identified a distinct color gradient in the belt, with reddish space rocks clustering near the inner edge and bluer asteroids found farther out. These differences have been attributed to thermal weathering, with the redder rocks being more thermally treated than the relatively pristine bluer asteroids.

Many researchers thus thought that most of the asteroids in the belt had not moved away from the orbits in which they formed. But new findings have belied the notion of a static asteroid belt, the researchers said.

“This trend does not hold for smaller sizes, suggesting that the solar system was more dynamic than originally expected,” DeMeo told via email.

Indeed, the distribution and composition of asteroids in the belt suggest that Jupiter moved toward the sun early in the solar system’s history, perhaps approaching as close to our star as Mars is today. today, according to the researchers.

“Jupiter would have moved through the primordial asteroid belt, emptying it and then repopulating it with scrambled material from both the inner and outer solar system as Jupiter then reversed course and headed towards the outer solar system. “, DeMeo and Carry write, noting that further observations should determine how closely this scenario represents reality.

While recent asteroid surveys shed light on the history of our own solar system, they could also reveal information about the formation and evolution of exoplanet systems, the researchers said.

“Our solar system is sort of the gold standard for planetary systems; we have so much more detail about our own solar system that it can help fill in the gaps with extrasolar systems,” DeMeo told SPACE. com via email. “The understanding goes both ways, though, because the idea of ​​planetary migration and a more dynamic planetary system history has really been propelled by what we’ve seen around other stars.”

While astronomers have come a long way over the past decade, there’s still a lot to learn about asteroids, say DeMeo and Carry. For example, little is known about the interior structure of space rocks.

“Asteroid interiors are terra incognita for the next generation of asteroid researchers,” they write. “The interior of an asteroid reveals its thermal history, which constrains the initial conditions of the protoplanetary disk during planetesimal formation.”

NASA’s Dawn spacecraft recently provided a rare glimpse inside the massive asteroid Vesta, and the probe will return similar data to Ceres – the largest body in the asteroid belt – when it arrives on the protoplanet next year.

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