The pristine Winchcombe meteorite suggests that Earth’s water came from asteroids

The Winchcombe meteorite was discovered in a field by researchers from the University of Glasgow in Scotland. SPIRE GLOBAL, MIRA IHASZ, UNIVERSITY OF GLASGOW

A coal-dark space rock the size of a soccer ball fell through the sky over northern England late in the evening of February 28, 2021. The rock blazed in an eight-second streak of light, then split into fragments and sped toward Earth. The largest piece landed in the driveway of Rob and Cathryn Wilcock in Winchcombe, a small, historic town.

Scientists report in Science Advances on November 16 that an analysis of those fragments reveals that the meteorite came from the outer solar system and contains water that is chemically similar to Earth's. One of science's unsolved mysteries is how Earth got its water. The new findings back up the theory that asteroids brought water to the young planet (SN: 5615).

The Wilcocks were not the only ones who discovered pieces of the fallen rock that night. They were, however, the first. Parts of the Winchcombe meteorite were collected within 12 hours of impact, indicating that they are relatively uncontaminated with earthly material, according to planetary scientist Ashley King of London's Natural History Museum.

The first pieces of the Winchcombe meteorite were discovered in the driveway of Rob and Cathryn Wilcock in England. The meteorite shattered on impact, leaving only a small dent in the driveway. WILCOCK, R.

The first pieces of the Winchcombe meteorite were discovered in the driveway of Rob and Cathryn Wilcock in England. The meteorite shattered on impact, leaving only a small dent in the driveway. Wilcock, R.

Other meteorites have been recovered after being tracked from space to the ground, but never in such a short period of time (SN: 122012).

"It's as pristine as we'll get from a meteorite," King says. "Other than landing it on my desk at the museum or sending a spacecraft up there, we can't really get them any faster or more pristine."

After collecting approximately 530 grams of meteorite from Winchcombe and other locations, including a sheep field in Scotland, King and colleagues applied every lab technique under the sun to the samples. To determine what elements and minerals were present in the material, the researchers polished it, heated it, and bombarded it with electrons, X-rays, and lasers.

The team also examined footage from the UK Fireball Alliance, a collaboration of 16 meteor-watching cameras from around the world, as well as footage from doorbell and dashboard cameras. The films aided in determining the meteorite's trajectory and origin.

The meteorite is a carbonaceous chondrite, a rare, carbon-rich rock discovered by the team. It originated from an asteroid near Jupiter's orbit and began its journey toward Earth around 300,000 years ago, a relatively short time for a trip through space, according to the researchers.

Chemical analyses revealed that the meteorite is approximately 11% water by weight, with the water locked in hydrated minerals. Some of the hydrogen in that water is deuterium, a heavy form of hydrogen, and the meteorite's hydrogen-to-deuterium ratio is similar to that of the Earth's atmosphere. "It's a good indication that water [on Earth] came from water-rich asteroids," says King.

The meteorite pieces also contained amino acids and other organic material, according to the researchers. "These are the fundamental building blocks for things like DNA," King explains. "They don't contain life, but they have the beginning of life locked up in them." More research will be needed to determine how those molecules formed in the asteroid from which the meteorite came, and how similar organic material could have been delivered to the early Earth.

"It's always exciting to have access to material that can provide a new window into an early time and place in our solar system," says Arizona State University in Tempe planetary scientist Meenakshi Wadhwa, who was not involved in the study.

She hopes that future research will compare Winchcombe meteorite samples to asteroids Ryugu and Bennu, which were collected by spacecraft and returned to Earth (SN: 11519). Both of these asteroids are closer to Earth than the main asteroid belt, from which the Winchcombe meteorite originated. By comparing and contrasting all three samples, we can get a better picture of the early solar system's composition and how it evolved into what we see today.


The Winchcombe meteorite, a one-of-a-kind and pristine witness from the outer solar system, was discovered by A. King et al. Science progresses. doi:10.1126/sciadv.abq3925. Published online November 16, 2022.


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