Weathering of Chondritic Meteorites

Terrestrial modification of the Ivuna meteorite and a reassessment of the chemical composition of the CI type specimen

“…All meteorites are susceptible to terrestrial alteration as soon as they enter the Earth's atmosphere (e.g. Bland et al 2006). The CI carbonaceous chondrites are all falls (excluding the Antarctic CI finds that probably belong to separate chondrite group, King et al 2019b), but as highly porous and volatile-element rich rocks they are particularly vulnerable to terrestrial modification and are known to experience mineralogical and chemical changes (Berzelius 1834;Zolensky 1999;Gounelle and Zolensky 2001;Velbel and Palmer 2011).…”

“…Most meteorites are finds recovered from hot and cold deserts and exposed to terrestrial weathering for several thousands to millions of years (e.g. Bland et al 2006). A much smaller number of meteorites are witnessed falls that were recovered soon (hours to years) after landing on Earth fragile, porous and chemically volatile nature are highly vulnerable to terrestrial alteration.…”

Mineralogy, chemistry, and composition of organic compounds in the fresh carbonaceous chondrite Mukundpura: CM1 or CM2?

“…Mukundpura seems to be excluded from the general trend with a deeper organic feature compared to the other meteorites with similar measured reflectance. As some of the organic matter in carbonaceous chondrites is the most likely material to be destroyed by weathering conditions (Bland et al 2006), the reflectance spectra of falls should present deeper organic features than finds, as is the case for the freshly fallen Mukundpura. Note however, that the trend in Figure 12 relies upon CM and heated CM, and more measurements on non-heated CM are required to confirm the trend.…”

Revealing High‐Manganese Material on Mars at Microscale

“…This texture indicates that the high-Mn materials were formed before NWA 11220 was ejected from Mars ZENG ET AL. and/or fell to the Earth because terrestrial weathering products commonly fill the pre-existing fractures in meteorites; (c) Previous works showed that the alteration of hot desert meteorites is mineralogically characterized by the replacement of primary Fe 0 -and Fe 2+ -minerals (e.g., Fe-Ni metal, troilite, and silicates) by weathering products (e.g., goethite, lepidocrocite, barite, and gypsum; Bland et al, 2006;Hyde et al, 2014;Lee & Bland, 2004). No Mn-rich mineral phases (e.g., Mn > 20 wt%) were recognized as terrestrial products within desert meteorites, because of the relatively low Mn content in the primary Fe 0 -and Fe 2+ -minerals (e.g., Fe-Ni metal, troilite, and silicates).…”

“…No Mn-rich mineral phases (e.g., Mn > 20 wt%) were recognized as terrestrial products within desert meteorites, because of the relatively low Mn content in the primary Fe 0 -and Fe 2+ -minerals (e.g., Fe-Ni metal, troilite, and silicates). For the mineral assemblage of high-Mn material (e.g., apatite, enstatite, and amorphous Mn-bearing material; Figure 2) in Clast-MN1, these mineral phases are not the typical terrestrial weathering products of the desert meteorites (e.g., chondrites or lunar meteorites; Bland et al, 2006;Hyde et al, 2014;Lee & Bland, 2004). It is reasonable to indicate that the high-Mn material cannot be explained by the terrestrial processes on the Earth; and (d) In particular, Mn-rich glasses (Mn = 4.8-5.6 wt%) have been observed in the fusion crust of the breccia meteorite NWA 7034 (Liu et al, 2021).…”