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Scientists at the Southwest Research Institute studied an unusual pair of asteroids and discovered that their existence indicated an early planetary rearrangement in our solar system.
These bodies, called Patroclus and Menoetius, are the targets of NASA's next mission to Lucy. They are about 70 miles wide and revolve around the Sun. They are the only big known binary in the population of ancient bodies called Trojan asteroids. The two swarms of Trojans orbit about the same distance from the sun as Jupiter, a swarm in orbit ahead and the other behind, the gas giant.
"The Trojans were probably captured during a dramatic period of dynamic instability when a skirmish between the giant planets of the solar system – Jupiter, Saturn, Uranus and Neptune – occurred," said David Nesvorny. , researcher at the SwRI institute. He is the main author of the article entitled "Evidence of a very early migration of planets from the solar system from the Trojan Jupiter binary Patroclus-Menoetius", published in Nature Astronomy. This reshuffling pushed Uranus and Neptune outward, where they encountered a large primordial population of small bodies believed to be the source of the current Kuiper Belt objects, which orbit the edge of the solar system. "Many small bodies of this primordial Kuiper Belt were scattered inward, and some of them became Trojan asteroids."
A major problem with this model of evolution of the solar system however was when it occurred. In this article, scientists demonstrate that the very existence of the couple Patroclus-Menoetius indicates that dynamic instability between giant planets had to occur during the first 100 million years of the formation of the solar system.
Recent models of small body formation suggest that these types of binaries are the remnants of the early days of our solar system, when pairs of small bodies could form directly from a cloud of pebbles.
"The Kuiper Belt observations of today show that binaries like these were quite common in ancient times," said Dr. William Bottke, director of the department's space studies department. SwRI, who co-wrote the document. "Only a few now exist in the orbit of Neptune, the question is how to interpret the survivors."
If instability had been delayed several hundred million years, as suggested by some models of solar system evolution, collisions within the primordial disk would have disrupted these relatively fragile binaries, leaving no capture in the Trojan population. Previous dynamic instabilities would have left more binaries intact, increasing the probability that at least one of the binaries was captured in the Trojan population. The team has created new models that show that the existence of the binary Patroclus-Menoetius strongly indicates an earlier instability.
This model of early dynamic instability has important consequences for terrestrial planets, especially with regard to the origin of the large craters of impact on the Moon, Mercury and Mars, formed about 4 years ago. billion years. The impactors that created these craters are less likely to have been projected from the outer regions of the solar system. This could imply that they were created by the remnants of small bodies of the formation process of the earthly planet.
This work highlights the importance of Trojan asteroids to illuminate the history of our solar system. Much more will be learned about the Patroclus-Menoetius binary when NASA's Lucy Mission, led by SwRI researcher and co-author Hal Levison, will study the couple in 2033, culminating in a 12-year mission.
This work was funded by the Virtual Research Institute for Solar System Exploration (SSERVI) and NASA's Emerging World Programs. SwRI researchers are part of 13 teams at SSERVI, based and managed at NASA's Ames Research Center in Silicon Valley, California. SSERVI is funded by the Scientific Missions Directorate and the Human Exploration and Exploitation Mission Directorate at NASA headquarters in Washington. Lucy is a Discovery class mission that will address key scientific questions about the solar system. NASA's Goddard Space Flight Center in Greenbelt, Maryland, will provide overall mission management, and Lockheed Martin Space Systems in Denver will build the spacecraft. Discovery missions are overseen by the NASA Marshall Space Flight Center Planetary Missions Program Office in Huntsville, Alabama, for NASA's Planetary Science Division.
For more information, see: https://www.swri.org/planetary-science or DOI: 10.1038 / s41550-018-0564-3.
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