Allan Hills A77003 meteorite, Allan Hills, Victoria Land, Eastern Antarctica, Antarcticai

Regional Level Types
Allan Hills A77003 meteorite	Meteorite Fall Location
Allan Hills	Group of Hills
Victoria Land	Region
Eastern Antarctica	Region
Antarctica	Continent

Carbonaceous Chondrite (CO3.6; S1; W1)
Find, 1977; 780 g

A small rounded stone with its top surface still covered with a dark glassy fusion crust was recovered from the Antarctic ice. While some staining has affected the bottom surface, upon inspection the meteorite is a relatively unweathered assemblage of well-defined chondrules accompanied by various small fragments and inclusions within a very fine-grained, dark matrix. Chondrules are mostly olivine rich (porphyritic and granular olivine [PO, GO]). Individual mineral grains and fragments are mostly olivine and orthopyroxene, somewhat variable in composition but usually Mg-rich. When recovered in 1977, ALHA77003 was only the 2nd CO (Ornans-like) carbonaceous chondrite recovered from Antarctica and only the 4th CO find. Two other CO chondrites were also recovered in the same year, but today the count of Antarctic COs listed is now approaching 300. [As of mid-2015, most of the ~290 records refer to small stones which undoubtedly represent a much smaller number of individual falls.]

For such a small stone ALHA77003 has received a healthy amount of attention during the past few decades. Much of the interest has been in separating possible effects of terrestrial weathering from hydrous metamorphism on the ALHA77003 original homeworld. Apparently, the mineral assemblages were altered by intermittent activities on a small world with its own endowment of ice several billion years before the meteorite fell onto the Antarctic ice. Other metamorphic activity of interest involve the small CAI spinel-rich assemblages, usually rimmed with phases out of equilibrium with the interior. Much of this metamorphic activity presumably occurred in earlier, much warmer regions of the ancient solar nebula.


Nota Bene: In the literature the meteorite is frequently called 'Allan Hills 77003' and 'ALH77003' (following simpler naming conventions adopted after the meteorite had been formally named).

Other Regions, Features and Areas containing this locality

References