Winchcombe meteorite gets official classification

Jonathan Amos
Science correspondent
@BBCAmoson Twitter

Published
image copyrightNHM
image captionThe national collection at the NHM holds in total 548g of stones and powder

The Winchcombe meteorite is now official.

The rocky material that fell to Earth in a blazing fireball over the Cotswold town of Winchcombe in February has had its classification formally accepted.

Details have just been published by the international Meteoritical Society in its bulletin database.

Early work by UK scientists indicates the Winchcombe object dates back to the very beginning of the Solar System, some 4.6 billion years ago.

This makes it extremely valuable. Certainly, it is the most important space rock ever to fall and be recovered in Britain.

Formal classification basically means the dark grey-to-black material picked up in Gloucestershire earlier this year is now absolutely recognised as being meteoritic in nature, and it means also that the name "Winchcombe" can be used to describe it.

media captionAshley King discusses the classification with the BBC's Roland Pease

The entry in the database is akin to a birth certificate. It tells the story of the fall - observed by numerous cameras and eyewitnesses - and the process of retrieval, and it includes some initial statements about Winchcombe's chemistry.

Researchers, led from London's Natural History Museum (NHM), say the meteorite - comprising 548g of small stones and powder - is a member of the CM2 carbonaceous chondrites.

Winchcombe is said to be "Mighei-like", which is a reference to a particular type specimen, or standard, of meteorite that was found in Ukraine in the late 19th Century.

"Carbonaceous chondrites are probably the oldest and most primitive extra-terrestrial materials we have available to study," said the NHM's Dr Ashley King.

"They come from asteroids that formed right back at the start of our Solar System.

"They're like time capsules. They're telling us about the building blocks of our Solar System. Obviously, we weren't there 4.6 billion years ago, and these meteorites are a way for us to actually see what sort of materials were there, and how those materials started to come together to make the planets," he told the Science In Action programme on the BBC World Service.

image copyrightRob Wilcock
image captionMore than 300g famously fell on the driveway of the Wilcock family

Winchcombe is mostly made up of phyllosilicates, or clays. These are minerals that result from silicate rocks as they come into contact with water. The H2O is bound up in those minerals.

The specific isotopic, or atomic, signature of this water will be measured and compared with what we know about the water here on Earth.

Theory holds that a bombardment of the parent asteroids of meteorites like Winchcombe could have delivered much of the H20 we now see in our oceans.

The carbon content of Winchcombe is in the order of a few percent. It's in the organics in the meteorite. This, obviously, is chemistry that fascinates researchers because it lies at the basis of life.

We don't have traces of biological activity on Earth until almost a billion years after the Solar System's formation, but studying meteorites such as Winchcombe could give us clues to the chemical "feedstock" that got life going on our planet.

Nearly everything that was recovered in and around the Cotswold town is now in the national collection at the NHM. There's probably only about 100g in private hands.

Analysis suggests the object that hit the top of the atmosphere on 28 February may have weighed 50-60kg and measured several 10s of cm across. Very little of this survived the fiery descent to the ground.

The opening studies on Winchcombe have been funded by the Science and Technology Facilities Council.

This has allowed for the purchase of a special curation facility to keep the meteorite material in perfect condition.

It takes the form of a nitrogen-filled box about the size of a large chest of drawers.

The box has holes in it with gloves attached, rather like washing-up gloves but thicker. It means researchers can put their hands through to manipulate the meteorite samples without having to bring them back into contact with air.

"Carbonaceous chondrites like Winchcombe are used to being in the cold vacuum of space, and they start to react with the atmosphere, especially water and oxygen, as soon as they land on Earth," explained Prof Sara Russell from the NHM.

"We want to keep the material as fresh as possible, and as closely equivalent to returned (space) mission samples as possible. Also, we already know that Winchcombe is full of organic material, and we want to make sure that this does not become contaminated by the huge amount of organics crawling all around the surface of Earth," she told BBC News.

Science In Action with presenter Roland Pease is broadcast weekly on the BBC World Service. The first airing of an episode is on Thursdays at 19:30 GMT (20:30 BST). It can then be listened to on demand on BBC Sounds.