New clues on solar system evolution and origin of habitable Earth
Illustration of solar wind flowing over asteroids in the early solar system. The magnetic field of the solar wind (white line/arrows) magnetizes the asteroid (red arrow). Researchers at the University of Rochester used magnetism to determine, for the first time, when carbonaceous chondrite asteroids first arrived in the inner solar system. (University of Rochester illustration / Michael Osadciw)
In a new paper published in the journal Nature Communications Earth and Environment, researchers, including Alexander Krot at the Hawai‘i Institute of Geophysics and Planetology, used paleomagnetic records to determine when carbonaceous chondrite asteroids, some of which are rich in water and organics, first arrived in the inner solar system. The research helps inform scientists about the early origins of the solar system and why some planets, such as Earth, became habitable and were able to sustain conditions conducive for life, while other planets, such as Mars, did not.
The research also gives scientists data that can be applied to the discovery of new exoplanets, planets that orbit stars outside of the solar system and the search for other habitable planets.
Some meteorites are pieces of debris from outer space objects such as asteroids. After breaking apart from their “parent bodies,” these pieces are able to survive passing through the atmosphere and eventually hit the surface of a planet or moon.
Studying the magnetization of meteorites can give researchers a better idea of when the objects formed and where they were located early in the solar system relative to the sun.
The CV (Vigarano type) carbonaceous chondrite Allende fell to Earth and landed in Mexico in 1969 and has since become one of the most studied meteorites. It is the largest carbonaceous chondrite on Earth and contains pebble-sized objects—calcium-aluminum inclusions—that are thought to be the first solids formed in the solar system.
New experiments by University of Rochester graduate student Tim O’Brien, the first author of the paper, found that magnetic signals in the meteorite were not actually from the dynamics of a planet forming an iron core, as prior researchers had interpreted. Instead, O’Brien found, the magnetism is a property of Allende’s unusual magnetic minerals produced during metasomatic alteration experienced by the CV chondrite parent asteroid.
“The metasomatic alteration recorded by Allende resulted from water and carbon dioxide-rich fluid-rock interaction at about 300-400 degrees Celsius about 3-4 million years after formation of the solar system and is quite unique among carbonaceous chondrites,” said Krot.
Having solved this paradox, O’Brien was able to identify meteorites with other minerals that could faithfully record early solar system magnetizations.
John Tarduno, co-author and lead professor at the University of Rochester’s magnetics group, combined this work with theoretical work and computer simulations. These simulations showed that solar winds draped around early solar system bodies and it was this solar wind that magnetized the bodies.
Using these simulations and data, the researchers determined that the parent asteroids from which carbonaceous chondrite meteorites broke off arrived in the Asteroid Belt from the outer solar system about 4,562 million years ago, within the first five million years of solar system history.
The analyses and modeling offers more support for the so-called Grand Tack theory of the motion of Jupiter. While scientists once thought planets and other planetary bodies formed from dust and gas in an orderly distance from the sun, today scientists realize that the gravitational forces associated with giant planets—such as Jupiter and Saturn—can drive the formation and migration of planetary bodies and asteroids. The Grand Tack theory suggests that the inner and outer solar system asteroids (non-carbonaceous and carbonaceous, respectively) were separated by the gravitational forces of the giant planet Jupiter, whose subsequent migration then mixed the two asteroid groups.
“This early motion of carbonaceous chondrite asteroids sets the stage for further scattering of water-rich bodies—potentially to Earth—later in the development of the solar system, and it may be a pattern common to exoplanet systems,” said Tarduno.
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