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| EETA79001 | |
|---|---|
| Name | EETA79001 |
| Type | Shergottite (Martian meteorite) |
| Country | Antarctica |
| Region | Elephant Moraine, Transantarctic Mountains |
| Found | 1979 |
| Total known weight | ~790 g |
| Group | Basaltic shergottite |
EETA79001 is a basaltic shergottite meteorite recovered from the Antarctic ice field in 1979 during a coordinated United States Antarctic Program field season near Elephant Moraine in the Transantarctic Mountains. It is one of the classic meteorites that contributed to establishing a well-supported link between a subset of meteorites and the planet Mars, and it has been the subject of extensive petrologic, isotopic, and geochemical study by teams from institutions such as the Smithsonian Institution, California Institute of Technology, and the University of Washington. The specimen comprises multiple lithologies and glassy impact-melt lithologies that provided key evidence for volatile, shock, and crystallization histories relevant to Martian igneous processes.
EETA79001 was collected during an expedition led by personnel from the United States Antarctic Research Program and curated through transfers involving the US National Museum of Natural History, later studied by researchers affiliated with the Jet Propulsion Laboratory, NASA Johnson Space Center, and the Institute of Meteoritics. Initial classification placed the specimen within the shergottite clan, alongside named meteorites such as Shergotty, Nakhla, and Chassigny that together form the historical SNCh grouping used in early Martian meteoritic studies. Subsequent classification refined EETA79001 as a basaltic shergottite based on its texture, mineralogy, and oxygen isotopic compositions compared with standards from the International Meteorite Nomenclature Committee and comparative analyses using samples handled at the Max Planck Institute for Chemistry.
Macroscopically, EETA79001 displays a fine- to medium-grained igneous texture with dark basaltic groundmass and feldspathic phases visible in polished sections prepared at facilities including the American Museum of Natural History and the Natural History Museum, London. Bulk chemical analyses published by teams at the Université Paul Sabatier and ETH Zurich report major-element affinities typical of mafic to intermediate basalts, with moderate levels of silicon, magnesium, iron, and calcium consistent with tholeiitic to transitional basaltic compositions recognized in Martian samples. Trace-element patterns measured using techniques at the Scripps Institution of Oceanography and Lawrence Livermore National Laboratory exhibit light rare earth element enrichments and compatible high field strength element signatures that have been compared with data from Martian igneous rocks analyzed by the Mars Science Laboratory Curiosity payload and orbital spectrometers on Mars Reconnaissance Orbiter.
Detailed petrographic work by investigators at the University of New Mexico and Brown University revealed a mineral assemblage dominated by pyroxene, maskelynitized plagioclase, and accessory chromium-bearing spinel, with interstitial glass and shock-melt veins. Pyroxene compositions trend from pigeonite to augite, a feature also described in other basaltic shergottites such as QUE 94201 and Zagami, and spinel chemistry overlaps data from studies at the Swiss Federal Institute of Technology. Shock features include planar deformation in pyroxene and maskelynite occurrence studied with transmission electron microscopy at the Los Alamos National Laboratory and electron microprobe analyses carried out at the University of Chicago; these shock signatures were central to linking shock histories to ejection scenarios discussed by researchers at the National Aeronautics and Space Administration and the Russian Academy of Sciences.
Isotopic systems investigated in EETA79001 include oxygen, chromium, neodymium, samarium–neodymium, rubidium–strontium, and various noble gases. Oxygen three-isotope measurements performed at the Carnegie Institution for Science and University of Tokyo showed non-terrestrial Δ17O values aligning with the Martian fractionation line identified in other SNC meteorites, while chromium isotopic anomalies reported by the University of Grenoble further tied its source region to Mars. Radiogenic isotopic age determinations using Sm–Nd and Rb–Sr methods by teams at the Max Planck Institute for Solar System Research and Imperial College London yielded crystallization ages within the young igneous range characteristic of shergottites, and cosmic-ray exposure ages derived from noble gas work at the ETH Zurich informed estimates of the timing of ejection from the Martian surface.
Interpretations of EETA79001’s petrogenesis have ranged from derivation by partial melting of a depleted Martian mantle source to crystallization in shallow magmatic intrusions, with comparative models developed by groups at the Institute for Planetary Materials and Southwest Research Institute. The presence of glassy melt pockets and high-pressure phases informed ejection models invoking large impact events on Mars, such as those analogized with craters studied by the Mars Reconnaissance Orbiter and impact chronologies discussed in relation to basins like Hellas Planitia. Thermal modeling undertaken by researchers at the University of Arizona and California Institute of Technology supports rapid cooling histories for some lithologies, consistent with eruption or emplacement near the surface prior to impact-driven launch.
EETA79001 has played a pivotal role in building the case for a Martian origin for certain meteorite classes; influential studies from teams at the Smithsonian Institution, Caltech, NASA Goddard Space Flight Center, and the University of Paris integrated isotopic, mineralogical, and shock data to argue for Mars as the source. The specimen has been a reference in debates over SNC nomenclature, Martian mantle heterogeneity, and the interpretation of in situ Martian data from missions including Viking, Mars Pathfinder, Spirit, and Perseverance. Ongoing analyses using new microanalytical techniques at institutions such as the Lawrence Berkeley National Laboratory and collaborations among the International Union of Geodesy and Geophysics continue to refine models of Mars’ igneous evolution using EETA79001 as a cornerstone sample.
Category:Martian meteorites