Angra dos Reis meteorite

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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 / -22.967; -44.317Coordinates: 22°58′S 44°19′W / 22.967°S 44.317°W / -22.967; -44.317
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[edit]

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[edit]

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[edit]

  1. ^ "Angra dos Reis". Meteoritical Society. Retrieved 3 January 2013. 
  2. ^ "Angra dos Reis". Meteoritestudies. Retrieved 3 January 2013. 
  3. ^ "The Angrite Meteorite Mystery" (PDF). NASA.