Abee
A 107-kilogram enstatite chondrite that fell on a Canadian wheat field in 1952 – a rare sample of rock formed with almost no oxygen.
Key facts
- Type
- Enstatite chondrite (EH4, impact-melt breccia)
- Fell or found
- Fell (witnessed)
- Year
- 1952 (10 June)
- Country
- Canada (Alberta)
- Mass
- about 107 kg
- Official name
- Abee
Late on the night of 10 June 1952, people in central Alberta, Canada, saw a fireball and heard a loud explosion. A few days later, a farmer near the hamlet of Abee found a hole in his wheat field. Digging down, he and others recovered a single stone weighing about 107 kilograms. It turned out to be one of the largest and most important enstatite chondrites ever found.
A rare type of meteorite
Most chondrites, the stony meteorites made of small rounded grains called chondrules, belong to the ordinary chondrites or the carbonaceous chondrites. Enstatite chondrites are much rarer. They are named after their main mineral, enstatite, a magnesium silicate with almost no iron in it. What makes them special is the chemical environment in which they formed. Enstatite chondrites formed under extremely reducing conditions, with very little oxygen available. Iron, which in other meteorites is often combined with oxygen in silicate minerals, is instead found as metal or combined with sulphur.
As a result, enstatite chondrites contain minerals that are very rare or unknown in ordinary Earth rocks. These include sulphides of calcium, magnesium and manganese, such as oldhamite and niningerite, the latter named after the meteorite hunter Harvey Nininger. They also contain silicon dissolved in their metal, another sign of extremely low oxygen.
Enstatite chondrites are divided into two groups: EH, high in iron and metal, and EL, lower in iron. Abee is an EH chondrite, and it is one of the largest enstatite chondrites ever recovered from a witnessed fall.
A breccia with a history
Abee is not a simple rock. It is an impact-melt breccia, a rock made of fragments cemented together, with parts that were melted by impacts on its parent body. Under the microscope, scientists see angular clasts of chondritic material set within metal-rich areas that were once partly molten. Its history included both the original formation of the chondritic material and later violent collisions. Researchers have used Abee to study how impacts reshaped the surface of its parent asteroid.
A link to Earth?
Enstatite chondrites have an intriguing connection with our own planet. Their oxygen isotopes, the proportions of different forms of oxygen atoms, are almost identical to those of Earth and the Moon, while most other meteorites differ. Several other isotopic measurements also show close similarities. As a result, many scientists think that the material that built Earth was similar to enstatite chondrites in some important ways, although Earth's overall chemistry is not a perfect match. Abee, as one of the largest and best-studied enstatite chondrites, has been central to this research.
Enstatite chondrites also come up in discussions of the planet Mercury. Like aubrites, they show that some planetary building blocks formed with very little oxygen, and Mercury's iron-poor, sulphur-rich surface suggests that it formed under similar conditions.
Why it matters
Abee is a large, fresh and well-documented sample of a rare kind of meteorite. It allows scientists to study how rocks formed in an oxygen-poor part of the early Solar System, how unusual minerals crystallised, and how impacts altered them. It also contributes to one of the biggest questions in planetary science: what were the building blocks of Earth?
Specimens of Abee are held in Canadian collections and in museums around the world. Its story also shows how a farmer's careful attention can lead to an important discovery. If you find an unusual hole or rock after a fireball, report it, record its position, avoid handling the stone with bare hands, and contact a museum or university. Remember that meteorites belong to landowners in many places, so permission always comes first.
Did you know?
Abee was found in a farmer's wheat field a few days after the fireball.
Enstatite chondrites like Abee formed in an environment with almost no oxygen.
Their oxygen isotopes are almost identical to those of Earth and the Moon.