Northwest Africa 12264 Meteorite Stones Are Older Than Anticipated
Ben Hofnagers
Tiny chips from a singular meteorite may completely challenge our current understanding of the solar system’s formation, as it has proven to be older than initially thought.
Earlier research indicated that small, rocky entities known as protoplanets formed relatively later, scattered across the asteroid belt between Mars and Jupiter. Interestingly, it is believed that the inner regions formed around 4.563 billion years ago, a slightly older timeline compared to the inner protoplanet’s age of 4.566 billion years. This age discrepancy was presumed to be due to the outer regions containing more water and ice, which would have slowed the inner core’s melting process.
This timing gap, while brief in the grand scheme of cosmology, was long accepted as a component of our cosmic history. Now, according to Ben Ryder Stokes from the Open University in Milton Keynes, UK, this notion needs reevaluation.
Planetary formation is typically thought to occur through accretion, where dust and gas are pulled in by gravitational forces, followed by differentiation—where the accumulated material heats up, melts, and separates into cores, mantles, and crusts. This process was previously thought to unfold at slightly divergent times for the early solar system’s internal and external protoplanets, but that view is now under scrutiny.
The team’s pivotal finding centers on a small meteorite named Northwest Africa 12264. Weighing around 50 grams, it was acquired in 2018 from a dealer in Morocco. Researchers obtained consent from the owner to analyze fine particles shaved from the meteorite, revealing that the ratio of chromium to oxygen—which varies in known patterns throughout our solar system—indicated the stones originated from the outer regions.
The meteorite’s composition also indicated that it came from the area between the core and crust, specifically the mantle, marking the first sample found from the outer solar system’s mantle. “This planet must have undergone significant upheaval to expose material from such depths,” states Ryder Stokes. “There surely must have been a colossal impact involved.”
Crucially, however, the age determined through lead isotopes contradicts the prevailing belief that the outer protoplanet should be younger. “This finding is astonishing, as it implies some of the oldest materials in the solar system,” he explains. “It suggests that rocky planets formed simultaneously in both the inner and outer solar system.”
Sebastiaan Krijt from the University of Exeter in the UK notes that shifts in events occurring over millions of years may not seem exigent at the time, yet could have profound implications. Understanding the sequence of events that shaped the solar system and the interactions of the various processes involved is essential for studying both solar systems and star systems throughout the universe.
“These stages of formation are considerably brief, and a mere million years can create significant distinctions,” Krijt remarks. “Getting the chronology and sequence of events correct is of utmost importance.”
topic:
Source: www.newscientist.com
