The most mysterious asteroids in the solar system
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Loading... - Adhira Laghari
- 29 Jun 2022
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They're trapped.
Two swarms of curious, diverse space rocks — called Trojan asteroids — continuously journey around the sun, one in front of the gas giant Jupiter and one behind. Jupiter and the sun's gravity have combined to lock the Trojans into this immutable orbit. The asteroids can't leave. It's a major reason why Trojan meteorites likely don't land on Earth, meaning we don't have any samples of these distant, still largely mysterious objects.
But planetary scientists are keenly interested in the story of the Trojans. They suspect these icy rocks are captured relics of our solar system's formation some 4 billion years ago. If so, the Trojans are the smaller building blocks of planets. They can help tell us how Earth, and the other planets, came to be.
"This is the first reconnaissance of the Trojan swarms."
"If we want to understand ourselves, we have to understand these small bodies," Hal Levison, a planetary scientist who leads the unprecedented mission to investigate the Trojans, told Mashable.
The mission, named "Lucy" after the ancient remains of a fossilized human skeleton, will visit six different Trojan asteroids over its 12-year mission. It launched in 2021. "This is the first reconnaissance of the Trojan swarms," Levison said.
Captured cosmic capsules
A looming question is how primordial chunks of our early solar system got trapped in swarms around Jupiter. A leading theory (based on simulations of the planets' formation) is that in the nascent solar system, the now-distant giant planets (Jupiter, Saturn, Neptune, and Uranus) were closer to the sun, as opposed to being the far-off intensely frigid worlds they are today. Meanwhile smaller, icy objects — the Trojans — formed beyond the planets in the outer realms of our solar system.
But around 880 million years after the solar system formed, it underwent dramatic change for reasons still being investigated. The large planets became violently unstable, explained Levison, and reoriented themselves farther from the sun. This created an opening for outer objects (the Trojans) to ultimately get propelled near gravitationally-powerful Jupiter.
"That's when we think the Trojans got stuck," said Levison.
They've orbited in swarms around Jupiter ever since. They're thought to be pristine solar system remnants from billions of years ago. And that's what makes them so valuable.
Planets grow by innumerable collisions, amassing into the larger worlds we see today. The untarnished Trojans are the type of smaller rocky and icy objects that would have contributed to making planets. They are diverse "fossils" of planet formation, Levison emphasized. If we want to know how Earth formed into the habitable, cloudy, lush world we know today, we have to know what, exactly, formed it.
The Trojans hold those clues. We just have to get there. Read More...
