From field to Vault, how the largest Winchcombe meteorite was found

Just before 22.00 on 28 February, a bright yellow flame was seen streaking across the midnight-blue sky, followed by a sonic boom. This intriguing event was captured on several sky-monitoring cameras and excited scientists and citizen scientists up and down the country.

Meteorites fall towards Earth almost every night - they are usually tiny particles, like grains of sand, and make a bright streak - but they never reach the ground.

Occasionally, larger pieces of rock make it through the atmosphere, but these events are rare and unpredictable. This is where sky-monitoring camera networks such as the UK Fireball Alliance (UKFall), as well as numerous resident dashboard and doorbell cameras, come in handy.

That night in February, scientists observed a fireball on cameras and correctly predicted meteorites landing in and around the Cotswolds village of Winchcombe in southwest England.

Ashley King, a meteorite specialist at the Museum, says, 'Usually the brighter the fireball, the bigger the object. Because of that, we had suspicions we could have meteorites on the ground.'

The next day, a public appeal was broadcast on TV asking people to keep an eye out and collect meteorites in tin foil and plastic bags.

Ashley and other scientists across the UK, including Luke Daly, a planetary geologist from the University of Glasgow, organised a small group of people to search the area. It was important that the meteorites were collected quickly before they became contaminated or damaged.

'This type of meteorite reacts with the atmosphere really quickly,' explains Ashley. 'As soon as it comes through, it's modified. It ends up with a fusion crust so it's really black and shiny around the edges. Once it lands on the surface, all the minerals and elements inside start reacting with moisture in the air.'

Discovering meteorite pieces was quite a feat considering it was the middle of a lockdown, the weather was cold and miserable and the task of finding black rocks in mostly rural locations was like searching for a needle in a haystack.

Luke says, 'We were lucky with the weather. It was overcast but not rainy, which was perfect. Rainfall would have been detrimental to the meteorites.

'I didn't expect to find anything as the UK has dark and forested terrain. There are loads of places for the meteorites to get lost into. It's a game changer that we were able to find one.'

One of the largest pieces of meteorite landed on the driveway of the Wilcock family, and a few smaller pieces were found in nearby gardens.

But it wasn't until a week later that the biggest individual meteorite, weighing 152 grammes, was found on farmland by Mira Ihasz, a volunteer with the University of Glasgow search team.

Mira says, 'There were around 15 people searching for meteorites on Thursday morning. By Saturday, most people went home but Luke and I, along with Lydia Hallis and Aine O'Brien, two other scientists from the University of Glasgow, remained.

'My mum called me that morning to say, "I know that you are going to find the meteorite today. I can feel it."

'I don't think she knew how slim the possibility of finding a black rock in a field littered with sheep poo was. But 30 minutes later, I saw something that looked different. It was big, shiny and a little bronze, half-hidden in the soil.

'I called Luke over and he confirmed it was a meteorite. We couldn't believe it. We were overwhelmed. Luke was speechless. It felt like we had won the lottery.'   

Unfortunately, the soft stone had fractured when it hit the ground and fell into two pieces when pulled out of the mud. The largest piece is now on display in The Vault gallery at the Museum.

What's so special about the Winchcombe meteorite?

The Winchcombe meteorite is the first meteorite fall to be recovered in the UK in 30 years. It is also the first-ever carbonaceous chondrite - the most primitive and pristine meteorite that we know of - to be discovered in the UK. Carbonaceous chondrites contain all the materials that were present during the formation of the solar system about 4.6 billion years ago, and have not been modified since.

Ashely says, 'They are amazing ways for us to learn about what materials were there when our solar system was forming, how the organic material and the planets were made, where there was water and ice in the early solar system, and much more.'

Carbonaceous chondrites are incredibly rare and make up around 3% of all meteorites found on Earth. Nearly all of these have been found in Antarctica.

To have a carbonaceous chondrite meteorite fall in the UK and collected within such a short time is a success story. It offers scientists a unique opportunity to study the meteorite without worrying about terrestrial contamination.

Ashely says, 'From our analysis, we've found that this meteorite came from an object which has ice and water. It came from somewhere near Jupiter and has a chemistry very similar to the Sun.'

Recently, the meteorite was officially classified as the Winchcombe meteorite.

For something to be officially classified, an initial description needs to be submitted to a panel of around six people at the Meteoritical Society.

Ashley says, 'We knew that it was a carbonaceous chondrite pretty quickly just by looking at it. But during the initial analysis, we learned it belongs to the CM group. The C stands for carbonaceous and the M stands for Mighei, named after the type specimen for this group.'

Luke adds, 'We've sent out bits of the meteorite to various labs for analysis. It seems to be an incredibly complicated rock made up of loads of different rock types. Some areas are rich in one mineral, while others don't have that mineral at all.

'We'll hopefully see minerals in this meteorite that we don't typically see in other meteorites, like salts that quickly dissolve in water, because we were able to collect it so quickly before it rained. This will give us new insights into a range of processes in our solar system, such as the origin of water on Earth. We are going to spend the next 12 months trying to fit the pieces together.'

The Winchcombe meteorite is similar to the rock samples returned to Earth as part of the Japanese space mission Hayabusa2, and is currently being brought back from the near-Earth asteroid Bennu by NASA's OSIRIS-REx spacecraft.

While the Winchcombe meteorite may look like an unassuming piece of coal, it is a true relic of the past and a national treasure, which visitors can now see at the Museum.