Lunar Meteorite: “specimen 1153”

The only information available about this meteorite is in two abstracts, one for the 31st Lunar & Planetary Science Conference (2000) and the other for the 13th Goldschmidt Conference (2003), both by the late Dr. Keizo Yanai. The second abstract states that the meteorite was “found in Antarctica” but no details are given, including the mass. The description, mineral chemistry, and bulk composition (only data for major elements are provided in the abstracts) are all consistent with a feldspathic lunar meteorite. For that reason, I include it in the List. I am unaware of any photographs.

The meteorite does not have an accepted name because it has not been submitted for approval to the Nomenclature Committee of the Meteoritical Society. “Specimen 1153” is not an “official” meteorite.

A curious chemical feature of the published composition is that CaO is too high (18.05%) for the Al₂O₃ concentration (27.44%). CaO ought to be about 15.9% because CaO/Al₂O₃ is constant (0.58) among feldspathic rocks of the lunar highlands. High CaO is a characteristic of hot-desert meteorites that have undergone terrestrial alteration (e.g., Korotev et al., 2003). Most lunar meteorites from hot deserts contain calcium carbonate or calcium sulfate of terrestrial origin. Specimen 1153 has a CaO/Al₂O₃ of 0.66. None of the feldspathic lunar meteorites collected in Antarctica by ANSMET or NIPR have CaO/Al₂O₃ greater than 0.59. Also, the reported concentration of sulfur, 0.61%, is at least 100 times that expected for a lunar feldspathic breccia. Thus, I have to conclude that the stone contains a few percent gypsum and calcite, unlike any other lunar meteorites from Antarctica. Until someone called my attention to the 2003 abstract, I concluded that the stone was likely from a hot desert. If it is from Antarctica, then it must have been found in an environment, perhaps a glacial moraine or dry valley, where there were cycles of water accumulation and evaporation.

The Mg/Fe of specimen 1153 is at the low end of the range among feldspathic lunar meteorites. For this reason, there is no obvious potential pair among known lunar meteorites. The only other chemical anomaly is that the reported concentration of Na₂O is 70% of that typical for a feldspathic lunar meteorites; this anomaly may reflect an analytical problem, however. Overall, “specimen 1153” is compositionally most similar to MAC 88104/5.