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| CM chondrites | |
|---|---|
| Name | CM chondrites |
| Type | Carbonaceous chondrite |
| Class | CM group |
| Petrologic type | 1–2 |
| Composition | Phyllosilicates, magnetite, carbonaceous material, sulfides, silicates |
| Country | Multiple falls and finds |
| Observed fall | Some members (e.g., Murchison) |
| Fall date | Various |
CM chondrites CM chondrites are a class of carbonaceous chondrite meteorites that record early Solar System processes, aqueous alteration, and organic synthesis on small parent bodies. They are central to studies connecting meteoritics, cosmochemistry, and astrobiology, and have informed debates involving planetary accretion, aqueous alteration, and the delivery of volatiles to terrestrial planets. Researchers from institutions such as Smithsonian Institution, NASA, European Space Agency, Max Planck Society, and Japanese Aerospace Exploration Agency study CM specimens through missions, collections, and laboratory analyses.
CM chondrites are grouped by shared petrographic, mineralogical, and chemical attributes first recognized in early classification schemes developed by scientists at the Natural History Museum, London and the Field Museum of Natural History. Members show abundant matrix composed of fine-grained silicates and phyllosilicates, metal-sulfide nodules, and carbonaceous material; major examples include Murchison meteorite and Yamato (meteorite) finds. Their study intersects work conducted at laboratories such as California Institute of Technology, Massachusetts Institute of Technology, The Open University, and University of Tokyo with analytical techniques pioneered by groups at Lawrence Livermore National Laboratory and Argonne National Laboratory.
CM chondrites are assigned within the petrologic scale of the Van Schmus–Wood classification and often described as types 1.0–2.0 according to alteration. Classification systems built by researchers at NASA Johnson Space Center and the Planetary Data System use petrographic criteria established by investigators like those at the Lunar and Planetary Institute and the British Antarctic Survey. Petrographic components include chondrules, refractory inclusions, and matrix; texture studies use electron microprobe facilities at California Institute of Technology and University of Arizona and scanning electron microscopes common at the Jet Propulsion Laboratory.
Mineralogy of CM material includes phyllosilicates (e.g., serpentine-group phases), Fe-oxyhydroxides, magnetite, sulfides (pyrrhotite, pentlandite), and olivine and pyroxene relics. Chemical signatures feature elevated volatile-element abundances and isotopic compositions analyzed by teams at Scripps Institution of Oceanography, University of California, Berkeley, and the Max Planck Institute for Chemistry. Techniques such as secondary ion mass spectrometry developed at Swiss Federal Institute of Technology Zurich and mass spectrometers used at University of Manchester reveal oxygen, hydrogen, nitrogen, and carbon isotopic systematics linking CM material to other carbonaceous groups like CI chondrites and CR chondrites.
CM chondrites host a diverse array of organic compounds including amino acids, carboxylic acids, and insoluble organic macromolecules; seminal work on the Murchison meteorite by investigators connected to Monash University and University of Vienna highlighted chirality and indigenous organics. Studies involving laboratories at NASA Ames Research Center, European Molecular Biology Laboratory, and University of Tokyo employ gas chromatography–mass spectrometry and isotopic analyses to constrain synthesis pathways, including Fischer–Tropsch-type processes and ultraviolet photochemistry studied at California Institute of Technology and Stanford University. These findings inform hypotheses discussed at conferences hosted by American Geophysical Union and International Astronomical Union about exogenous delivery of prebiotic material to early Earth.
Aqueous alteration in CM parent bodies produced phyllosilicate-rich matrices, magnetite framboids, and secondary sulfates; pioneering models were developed by researchers affiliated with Brown University and University of Colorado Boulder. Laboratory experiments at Massachusetts Institute of Technology and University of Chicago simulate low-temperature aqueous alteration and fluid–rock interactions to reproduce mineral assemblages. Geochemical models using results from Carnegie Institution for Science and isotope work from Columbia University constrain water/rock ratios, temperature ranges, and timescales of alteration, with implications for thermal evolution models proposed by scientists at Caltech and Jet Propulsion Laboratory.
Famous CM falls and finds include the Murchison meteorite (Australia), Sutter's Mill (meteorite), Y-791198 and other Yamato (meteorite) specimens recovered by National Institute of Polar Research (Japan), and Antarctic finds cataloged by the United States Antarctic Program. Each specimen has been the focus of multi-institutional studies involving Smithsonian Institution, Natural History Museum, London, National Museum of Natural History (France), and university collections, yielding landmark papers in journals associated with organizations like the Royal Society and the Geological Society of America.
Models for CM parent bodies draw on accretion scenarios influenced by dynamical studies from groups at University of California, Santa Cruz and Princeton University exploring planetesimal formation in the protoplanetary disk and radial mixing invoked in models by researchers at University of Cambridge and Institut d'Astrophysique de Paris. Thermal and collisional histories examined by teams at Brown University and Southwest Research Institute propose porous, low-mass parent bodies that experienced internal heating from short-lived radionuclides such as 26Al studied by investigators at Lawrence Berkeley National Laboratory. Sample return missions like Hayabusa2 and OSIRIS-REx and analytic comparisons coordinated through NASA Johnson Space Center and the European Space Agency continue to test parent-body hypotheses and link CM material to primitive Solar System reservoirs.
Category:Meteorites