New analysis of Winchcombe meteorite reveals window into early solar system

Meteorites can provide an invaluable window into the early solar system, since most come from asteroids that formed around the same time as the planets (4.5 billion years ago). When they land on Earth, however, the fragments usually become contaminated and less informative. But on Sunday, February 28, 2021, planetary scientists received a godsend when a fireball streaked across the sky over the UK, eventually coming to rest on a driveway in Winchcombe, Gloucestershire. Within hours, researchers were on the scene recovering the resulting fragments and storing them safely. As a result, the Winchcombe meteorite fragments are among the most pristine available for analysis.

Overseen by the Natural History Museum in London, the Winchcombe fragments were distributed to several institutions across the UK, including the University of Oxford, for one of the most comprehensive meteorite analyzes ever undertaken.

The main mass of the Winchcombe meteorite recovered by the Wilcock family on March 1, 2021. Credit: Rob, Cathryn and Hannah Wilcock.

A witness to the early solar system

At the University of Oxford’s Department of Physics, the fragments were analyzed by Dr Katherine Shirley using infrared spectroscopy to map the mineral composition of the meteorite. This confirmed that the Winchcombe specimen belongs to a rare class of meteorites called CM carbonaceous chondrites, which originate from early asteroids in the asteroid belt. It is the first such meteorite to be found in the UK.

Other academic institutions involved in the study performed detailed imaging and chemical analyzes which revealed that the Winchcombe meteorite contains approximately 11% extraterrestrial water (by weight). Most of it is locked up in minerals that formed during chemical reactions between fluids and rocks on its parent asteroid in the early stages of the solar system. Additionally, the ratio of hydrogen isotopes in water closely resembled the composition of water on Earth.

Extracts from the Winchcombe meteorite also contained extraterrestrial amino acids – prebiotic molecules that are fundamental building blocks for the origin of life. As the composition of the Winchcombe meteorite is largely unmodified by Earth’s environment, these results indicate that carbonaceous asteroids played a key role in providing the ingredients needed to catalyze the oceans and life on Earth. primitive.

A magnetic memory

Another key part of the analysis was to assess the magnetic composition, which was led by the University of Oxford’s Department of Earth Sciences. James Bryson, Associate Professor of Mineralogy, explained: “The magnetic composition of a meteorite acts as an internal hard disk memory of the conditions of its formation. We have found that there is a particularly high abundance of a magnetic phase called magnetite present in an exotic and uncommon form. This type of magnetite only forms under specific conditions, which tells us that Winchcombe had a unique history. Our ongoing investigations are now trying to determine exactly what it was.

This future work will use the Department’s new state-of-the-art geo-quantum diamond microscope, one of only two in Europe. “This machine will allow us to perform magnetic analysis on much smaller samples than before, opening up a whole new avenue of research. It will breathe new life into planetary science,” Prof Bryson said.

The powdered Winchcombe meteorite sample used in the Oxford study.The powdered Winchcombe meteorite sample used in the study at Oxford University. Credit: Dr. Rowan Curtis.

Make a way to Earth

Meanwhile, research by Dr Rowan Curtis (Department of Physics) could help trace the path by which the Winchcombe meteorite made its way from the asteroid belt to Earth. Using a machine called a goniometer, he measured the scattering of light on the meteorite’s surface, allowing improved thermal models of the asteroids and further constraining the Yarkovsky effect. “When one side of an asteroid is illuminated by the Sun, it creates a differential heating effect that acts like a propeller,” he explained. “Over long periods of time, this effect can influence the trajectory of an asteroid. By mapping in detail the variations in light scattering and thermal absorption, we can more accurately trace the trajectory of the Winchcombe meteorite in the opposite direction.

“The Perfect Test”

The team agrees that it has been a privilege to work on such a pristine sample, but their in-depth analyzes have also been the ideal pilot for future investigations. For example, the University of Oxford is part of NASA’s OSIRIS-REx mission, which aims to return samples from an “early” carbonaceous asteroid in the solar system named Bennu. The spacecraft is expected to return to Earth in September 2023.

The study “The Winchcombe meteorite, a unique and pristine record of the outer solar system” is published in Science Advances.

Samples of the Winchcombe meteorite are currently on public display at the Natural History Museum in London, the Winchcombe Museum and The Wilson (Art Gallery), Cheltenham. You can also learn about meteorites and even touch the 4.5 billion year old Nathan meteorite by visiting the newly refurbished exhibits at the University of Oxford Museum of Natural History.

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