ALH84001 - Orthopyroxenite
Click the microscope button to view a thin section for this sample.
Click the microscope button to view a thin section for this sample.

Fact sheet

ALH84001 - Orthopyroxenite

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

-76.920278, 156.773611
Allan Hills, Antarctica
About this collection

This collection of meteorites includes Shergottites, Nakhlites and Chassignites (or SNC meteorites) which originate from the surface of the planet Mars.

They carry unique signals of the surface of the planet that allows scientists to study the composition and age of Martian rocks. The collection includes a sample of the famous ALH84001 meteorite, evidence from which was used in 1996 to begin the debate of 'life on Mars?'. 


Sample details

Collection: Martian Meteorites
orthopyroxenite achondrite
Rock-forming mineral
Category guide  
Category Guide
Refers to any word or phrase that appears in the individual rock names. Names are generally descriptive; they allow users to search for broad terms like ‘granite’ as well as more specific names such as ‘breccia’. However, the adjacent descriptions of the specimens captures a wider range of general words and phrases and is a more powerful search tool.
Refers to any word or phrase that appears anywhere in the descriptions of the specimens
Accessory minerals
Minerals that occur in very low abundance in a rock. They are usually not visible with the naked eye and contribute perhapssver, they often dominate the rare elements such as platinum group metals.
Rock-forming minerals
Minerals that make up the bulk of all rock samples and are also the ones used in rock classi?cation.
Selecting one or more period, for example 'Jurassic'.
A term used to group together related samples that are not already gathered into a single Collection. For instance, there is a ‘SW England granites’ theme that includes such rock types as granite, hydrothermal breccia, skarn and vein samples.
A general term used to label a rock sample. It is a useful way of grouping similar samples throughout a collection. Category names are often, but not exclusively, common rock names (e.g. granite, basalt, dolerite, gabbro, greisen, skarn, gneiss, amphibolite, limestone, sandstone).
The owner of the sample that appears in the collection. For example, NASA owns all the samples that appear in the Moon Rocks collection
We would like to thank the following for the use of this sample: