ALH84001 - Orthopyroxenite
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Fact sheet
Description: 

ALH84001 was found by geologist Bobbie Score during a snowmobile ride on December 27th, 1984 in the Far Western Icefield of Allan Hills. It was recognized as a most unusual rock, and was the first Antarctic meteorite to be processed from the 1984-5 field season. Field notes describe it as a highly shocked greyish-green achondrite with a 90% fusion crust. Where the fusion crust had spalled away the interior showed a uniform coarse-grained rock with a blocky texture. Preliminary laboratory investigations revealed the sample had a “shocked appearance” and patches of brown iron-rich carbonate were noted. At this time the sample was classified as a diogenite. It was only six years later that its true identity would be recognized, when electron microprobe analysis established it was a SNC meteorite and hence potentially of Martian origin (SNC is an acronym for three meteorites believed to have originated on Mars - Shergotty, Nakhla and Chassigny). Further evidence of a martian origin for ALH84001 comes from the chemical composition of gases inside black beads of glass-like material (maskelynite) that had bubbled up when the rock was ejected from Mars by a violent shock. The gases matched the Martian atmosphere as measured by the Viking space craft which sampled the atmosphere in 1976.

Location: Victoria Land, Antarctica
Find or Fall: Find
Date:  1984
Recovered weight: 1930.9 g
Group: SNC
Weathering grade: A/B

In Place
In Time
Location description: 
Allan Hills, Antarctica
Accuracy:
Location precision: 
Good
Timescale:
Not known
Ma = Millions of years ago
In Focus
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Type:
Type: 
meteorite
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