IMAGES FROM FABULOUS FROZEN FINDS, VOLUME 07, NUMBER 01
Figure 1. An artist’s rendition of an impact on the surface of an asteroid. Impacts such as this one mix asteroidal surface materials into a well-gardened regolith; and in rare examples, enough of the projectile survives intact to become a component of that regolith. The Howardites PRA 04401 and PRA 04402 contain abundant fragments of CM2 carbonaceous chondrite material and offering researchers a new pathway toward understanding regolith mixing on the Howardite parent body (thought to be the asteroid 4 Vesta). Image by Don Dixon, courtesy of the National Museum of Natural History, Smithsonian Institution. (Asteroid_impact.jpg, 48 KB)
Figure 2. Backscattered electron photomicrograph of RBT 04261, a newly discovered Olivine-phyric Shergottite. The image has been colored to bring out mineralogical differences. Dark purple is maskelynite (feldspar converted to glass by impact shock); pink is olivine; olive-green is pyroxene; and white is FeTi oxides. The high abundance of olivine is the characteristic feature of this group of shergottites and suggests a higher temperature melt that may more directly related to the mantle of Mars. Image by Emma Bullock, courtesy of the National Museum of Natural History, Smithsonian Institution. (RBT_04261_colorized.jpg, 352 KB)
Figure 3. Graph illustrating how LAP 04773 and LAP 04757 fall outside the normal ordinary chondrite H, L and LL subgroup classifications. In this plot the groups are separated by the relative amount of Fe in the silicate minerals pyroxene and olivine. These two minerals incorporate Fe oxide into their composition at different rates; and as a result variations in the amount of Fe oxide (and oxygen) available separate the three main ordinary chondrite subgroups. Falling on the same trend but with much less Fe oxide in both olivine and pyroxene than previously identified ordinary chondrites, the LAP meteorites may be harbingers of a previously unrecognized ordinary chondrite subgroup (the “HH’s”?). After Russell et al., (1998) The Burnwell, Kentucky, low iron oxide chondrite fall: Description, classification and origin. Meteoritics and Planetary Science 33, 853-856. (fs_vs_fa.jpg, 192 KB)
Field Portraits:
Listed below are the field portraits for the meteorites mentioned in the newsletter. These images are taken to document the setting of the find, and usually contain a grey box we call a "counter" used to show the size and field number for the specimen. These field numbers are randomly assigned and do not correspond to the final sample number used by the Smithsonian Institution and NASA's Johnson Space Center to curate the specimens. These images should be cited as originating from "The Antarctic Search for Meteorites Program, Case Western Reserve University"
The new Howardites:
The new Shergottites
The new Chondrites
A final note: For a more technical description of these specimens, including photomicrographs and curatorial lab photos, or to learn more about the availability of these samples for scientific research, visit the Antarctic Meteorite Newsletter website.