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Illustration of an artist showing the collision of two asteroids, producing the "families" that we see today. (Don Davis / University of Florida)
In the beginning, 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 have been lured into the rock-strewn belt that surrounds the sun between Mars and Jupiter.
But according to a study published Monday in the journal Nature Astronomy, it was 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 Southwest Research Institute who was not involved in the # 39; 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 elements have built our solar system. "If we can go back in time and see the asteroid belt produced by these fat 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 Earth. (For those who are concerned about the collisions of Asteroids, rest assured that Dermott is still studying this question.)
But when Dermott started looking through a database of objects close to Earth, he noticed something odd. were inclined, or i nclines, compared to the plan of the rest of the solar system.
"We do not think of the forces acting to produce this distribution," Dermott said. On the other hand, "if a big asteroid is broken and it has a steep tilt, then these fragments have the same tilt".
Scientists have already discovered that nearly half of the asteroids belong to five families. "But Dermott and his colleagues say their analysis suggests that the number is as high as 85%."
This discovery corresponds to other observations of the asteroid belt, says David Nesvorny, ap scientific scientist at SWRI who was not involved with the Dermott study.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 implies a significant, though noticeable, involvement: "Nesvorny said.
This discovery can help solve a question about the formation of the planet that has baffled scientists for years. According to the traditional history of the origin of the solar system, the planets formed slowly from accretion, the particles of the circumstellar disk clustering into large pebbles, then into slightly larger spheres, until they reach their current size.
But when scientists try to recreate this story with computer models, they break down. Rather than growing, these nascent planets tend to break up after reaching the size of pebble. How could this process result in bodies the size of those in the asteroid belt, not to mention entire planets?
Enter the "big born" hypothesis. 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 gas 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 that 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 for asteroid belts around Vega and Fomalhaut, stars only a few tens of light years away
"It's the next big step, and this happens in 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? "It's something we can finally discuss in meaningful terms."
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