Angra dos Reis meteorite
| Angra dos Reis | |
|---|---|
| Type | Achondrite |
| Group | Angrite |
| Composition | Fassaite (93%) |
| Country | Brazil |
| Region | Angra dos Reis |
| Coordinates | 22°58′S 44°19′W / 22.967°S 44.317°W |
| Observed fall | Yes |
| Fall date | 20 January 1869 |
| TKW | 1.5 kilograms (3.3 lb) |
The Angra dos Reis meteorite is the type specimen of the angrite group. It was observed when it fell to earth in 1869.[1]
Discovery and naming
The meteorite is named after Angra dos Reis, a municipality of Rio de Janeiro, Brazil. It fell on 20 January 1869 into the bay where the water was about 2 m deep. Two fragments were found by a diver the next day.[2]
Mineralogy
Although it is the type specimen of the angrites, Angra dos Reis is actually very different from most angrites. It is almost completely made from a rare form of pyroxene called fassaite. This makes it more like a pyroxenite than the typical angrite, which is similar to a basalt. The only other meteorite samples that contain fassaite are the Calcium-aluminium-rich inclusions found in the Allende meteorite. The reason for this exotic composition is thought to be partial melting of a chondritic precursor under redox conditions in which meteoric iron is unstable.[3]
References
- ^ "Angra dos Reis". Meteoritical Society. Retrieved 3 January 2013.
- ^ "Angra dos Reis". Meteoritestudies. Retrieved 3 January 2013.
- ^ "The Angrite Meteorite Mystery" (PDF). NASA.