Martian Meteorite Rain: Petrology, Elemental, and Isotopic Composition of Ten Recently Recovered Shergottites

1 feb. 2019 Lunar and Planetary Institute, Houston, USA

The number of unpaired Martian meteorites has increased remarkably in recent years, especially because of finds in northwest African countries. Within just the past year numerous new specimens have been recovered, such that the present total has reached 127, of which 111 are various sorts of shergottites. We have been conducting systematic petrologic and chemical studies of these specimens, and here we give a summary report about our latest findings.

Petrologic, Elemental, Isotopic, and Magnetic Characterization of Vesicular Hypabyssal Angrites Northwest Africa 12004 and Northwest Africa 12320

1 feb. 2019 Lunar and Planetary Institute, Houston, USA

Since the witnessed fall of Angra dos Reis in 1869 in Brazil, a total of 19 additional distinct angrite specimens have been found, mostly in northwestern Africa. The two latest members of this very diverse class of achondrites both have diabasic igneous textures, and although similar do not seem to be terrestrially paired. Here we describe their petrology, mineralogy and bulk elemental compositions, as well as their oxygen-chromium-sulfur isotopic and magnetic characteristics

Evidence for a Unique Carbonaceous Chondrite Parent Body ('CX') and Another One with a Dunitic Mantle

1 feb. 2019 Lunar and Planetary Institute, Houston, USA

The forensic reconstruction of former bodies which populated the early Solar System presents a considerable challenge, since it depends on the recognition of random pieces of those bodies recovered as meteorites. Although numerous bodies (some differentiated) must have existed then, it is likely that many were completely disrupted by collisions, only to be sampled more recently from the remnant debris.

Mineralogy and Bulk Composition of Lunar Mare Basalt Northwest Africa 12008

1 feb. 2019 Lunar and Planetary Institute, Houston, USA

Among the 150 or so known lunar meteorites, mare basalts are quite rare, numbering only 12 at this writing. Even more remarkable in this the 50th anniversary of the Apollo 11 landing in Mare Tranquillitatis is the fact that so far no lunar meteorites have been recovered which match the high-Ti basalts sampled at the Apollo 11 and Apollo 17 sites. On the other hand only some of the mare basalt meteorites (which must represent random ejecta from lunar near-surface regions) closely resemble those at the other landing sites.


A fresh 500 gram stone found in Mali is a relatively coarse grained gabbroic shergottite containing shock-melted intercumulus zones. Among the 108 unpaired Martian meteorites now recognized, only NWA 6342 exhibits some similar shock features.
NWA 11509 is a unique permafic non-poikilitic olivine gabbroic shergottite (possibly a magmatic cumulate) with intermediate ITE affinities but an aberrant Hf isotopic composition. Polycrystalline olivine, which was also recognized in intermediate shergottite NWA 6342, implies high temperature thermal annealing of shock-deformed grains. Rapid crystallization of interstitial, shock-produced vesicular melts resulted in regions of intergrown plagioclase+low-Ca pyroxene, as well as possibly immiscible “blobs” of residual evolved liquid, which in turn quenched rapidly to aggregates of skeletal grains.

Petrology and Bulk Composition of Ultramafic Olivine-Orthocumulate Shergottite Northwest Africa 11261

1 jul. 2017 Meteoritical Society (2017),

As the recovery of more unpaired Martian meteorites continues apace (almost exclusively in the barren desert regions of northwest Africa), previously unrecognized lithologies or geochemical varieties should be expected to be discovered. The latest example out of the 107 unpaired specimens now known is a 114.2 gram stone coated by reddish-brown weathering products. The dark green interior is much fresher, yet still contains some thin veinlets and grain boundary coatings of fine-grained calcite, presumably a product of terrestrial alteration.


3 feb. 2017 Lunar and Planetary Institute, Houston, USA

A 2220 gram stone found in 2016 in Morocco is a coarse grained poikilitic shergottite containing unusually large amounts of quenched shock melt as veins and pockets. Among the 101 unpaired Martian meteorites now recognized, NWA 10961 is most similar to ALHA 77005, Yamato 793605 and NWA 4797, and at least ten other Martian meteorites. However, the shock melt veining in NWA 10961 is much more prevalent.