Many asteroids could be remnants of 5 destroyed worlds, say scientists

At first, the solar system was little more than a cloud of dust and gas. Then cold temperatures shattered the center of the cloud, forming the sun. The fledgling star is lit with nuclear fusion, sending light and heat into the rotating circumstellar disk. Soon, this material melted into gaseous planets, ice giants and rocky worlds, creating the solar system we know today.

For years, asteroids were considered as the remnants of planetary formation. and who were drawn into the crowded belt of rocky remains that surrounds the sun between Mars and Jupiter.

But according to a study published Monday in the journal Nature Astronomy, these worlds were also pieces of worlds. A large majority of the half million bodies in the inner asteroid belt may actually be shrapnel from five parent bodies called "planetesimals," say the scientists. But the entangled orbits of these lost worlds meant that they were doomed to collide, producing fragments that also collided, producing even more fragments in a cataclysmic cascade that lasted for over 4 billion years. years.

A "mystery" of the asteroid belt, said Katherine Kretke, a global scientist at the Southwestern Research Institute who was not involved in the project. study. It could also help solve a debate about the formation of the eight planets – including the Earth.

"I find it really exciting that we can go back in time and potentially see what components have built our solar system. "If we can go back in time and see the asteroid belt created by these great planetesimals, it tells us something very definitive about the circumstances that shaped our own planet."

Lead author of the study, University of Florida astrologer Stanley Dermott did not necessarily seek to probe a mystery of solar system formation.He and his colleagues were examining data on the dynamics of the body in the inner asteroid belt in the hope of understanding what makes an object leave the belt – and potentially fly to the Earth. (For those who worry about collisions d & # 39; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; Asteroids, rest assured that Dermott is still studying this issue.)

But Dermott began to look through a b ase of data of objects close to the Earth. asteroids: Their orbits were inclined, or inclined, compared to the plane of the rest of the solar system.

"We could not think of forces acting to produce this distribution," Dermott said. "if a big asteroid is broken and it has a strong inclination, then these fragments have this same inclination."

Scientists have already known that about half of the inner belt asteroids belong to five "families". But Dermott and his colleagues say their analysis suggests this result corresponds to other observations of the asteroid belt, said David Nesvorny, a global scientist at SWRI who was not involved in the study. 39, study of Dermott. Asteroids that belonged to the same family tend to form groups in orbit and have similar chemical compositions.

The idea that asteroids are actually larger body fragments entails an important, if not obvious implication: "Nesvorny said.

This discovery may help solve a question about the formation of the planet which has baffled scientists for years.According to the traditional history of the origin of the solar system, planets form slowly from accretion, particles of the circumstellar disk clustering into large pebbles , then in slightly larger spheres, until they reach their current size.

But when scientists try to recreate this story with computer models, they fail. Rather than growing these nascent planets tend to break up after reaching the pebble size.How could this process result in bodies the size of those of the asteroid belt, without speaking r whole planets?

Enter the hypothesis of the "big nee". Nesvorny and many others now think that gravity comes into play once the clods in the circumstellar disk reach the pebble stage, quickly pulling together massive amounts of material to form a huge new planet. In the internal solar system, this has produced small rocky planets like the Earth; Further from the sun, we have gaseous giants

But in the space between Mars and Jupiter, the enormous gravity of the largest planet in the solar system may have made it difficult to cultivate. a big object, says Nesvorny. The smaller bodies that emerged, which were probably one-tenth the size of a planet such as the Earth, would not have survived the chaos and collisions that followed; they broke up and formed the asteroid belt that we know today.

Some questions remain about this theory. Tim McCoy, a geologist at the Smithsonian's National Museum of Natural History, pointed out that most meteorites that fall on Earth do not seem to come from grandparents. And Kretke suggested that the theory might work better if there were a few dozen parent bodies, rather than just five.

Meanwhile, Nesvorny noted that the inner belt houses only one-tenth of all asteroids – he hopes to see the analysis applied to the rest of the asteroid belt.

Dermott said he and his colleagues plan to address this issue next. And one day, he added, research can be applied to other solar systems. Astronomers have found evidence of asteroid belts around Vega and Fomalhaut, stars only a few tens of light-years away

"It's the next big step, and it's product of our lives, "said Dermott. "All the matter of the formation and evolution of the planets and the question of" What do we need to form an Earthlike planet elsewhere? "is something we can finally discuss in significant terms."