Name: Meteorite Hills 00400 This is an OFFICIAL meteorite name. Abbreviation: MET 00400 Observed fall: No Year found: 2000 Country: Antarctica [Collected by US Antarctic Search for Meteorites program (ANSMET)] Mass: 4.58 kg
Circumstances of Find (John Schutt, Tim McCoy) These 23 meteorites range in mass from 4583.8 to 3.2 grams. They occurred within 200 m on either side of a line 5.8 km long connecting the largest and smallest mass. Although larger masses tend to lie at one end and smaller masses at the other, the distribution is imperfect and a mixed-mass clump is found in the center. The lineation of the distribution is not a result of either ice exposure or search strategy, as a much larger, rectangular area of blue ice was exposed and searched and meteorites were recovered throughout this larger area. The lineation may suggest a relatively recent fall.
Macroscopic Description: Tim McCoy MET 00400, the largest of the masses at 4583.8 g, has an upper regmaglypt-covered surface with a shiny brown coating. A prominent peak is formed by the intersection of several regmaglypts. The lower surface appears to be an earlier generation of fusion crust, with much shallower and larger depressions and a brown, matte finish. The other masses, ranging from 3.2 to 205.1 grams, are irregularly shaped with a shiny brown fusion crust similar to the upper surface of MET 00400. Smaller regmaglypts and depressions are common. Rare knobby surfaces are likely weathered fusion crust. Macroscopic similarities strongly support the pairing of these 23 meteorites. Slices were removed from MET 00400 (4583.8 g), 00401 (205.1 g), 00402 (82.6 g), 00403 (58.5 g) and 00412 (8.7 g) for examination. These masses were chosen to sample the ranges of masses and locations within the distribution. MET 00400 and 00412 are separated by 5.3 km.
Microscopic Description: Tim McCoy All 5 meteorites are essentially identical (further supporting a pairing for all 23 meteorites) and a single description will suffice. The surfaces are dominantly covered by corrosion products up to ~200 microns in thickness. Corrosion does not penetrate into the interiors of these masses. Fusion crust is present in small patches, particularly in recesses along the surface of the meteorite. An a2 structure of atmospheric origin is present in many places along all masses and extends into the center of the meteorite up to 1 mm. The meteorites exhibit a medium octahedrite structure with original band widths of 1-1.5 mm and typically L/W of 15-20. Each mass exhibits a single orientation of the Widmanstatten pattern, suggesting the formation of each (and perhaps all) from a single austenite crystal. A large, polycrystalline troilite nodule (17 cm in diameter) is present in MET 00400. The interior structure is extensively heat-altered and dominated by recrystallized kamacite. Dimensions of recrystallized grains are typically 100-500 microns. The meteorite is a preterrestrially heat-altered medium octahedrite. It may be a member of group IIIAB and is similar to heat-altered members of that group (e.g., Joel's Iron; Buchwald, 1975)
4.58 kg
