DHOFAR 908

Nine individual stones with heterogeneous compositions were recovered by a German expedition searching in Wadi Quitbit, Dhofar, Oman. These individual stones had weights of 81.43 g, 46.58 g, 45.63 g, 25.05 g, 16.11 g, 12.11 g, 9.02 g, 6.97 g, and 2.56 g, with a total combined weight of 245.46 g. The expedition was searching within a strewn field which presently comprises the lunar pairing group members Dhofar 302, 303, 305, 306, 307, 309, 310, 311, 730, 731, 489 (which was found 24 km away), 908, 909, 911 (comprising nine separate stones), 950, and 1085. Terrestrial weathering has produced significant staining by hematite (R. Korotev).

The finder of the Dhofar 908 stone, Norbert Classen, adopted the term "Rosetta Stone" to describe the 81 g main mass of this lunaite due to its having three distinct lithologies, which link the diverse finds Dhofar 302, 303, 305, 306, 307, 309, 310, 311, 730, 731, and 489 together; most of these other stones represent only one of the three lithologies. Importantly, Dhofar 908 established a clear pairing relationship among all of the separate finds (see photo below).

Following the analysis at the Institut für Planteologie in Münster, these meteorites were classified as lunar feldspathic breccias, specifically impact melt breccias. Interestingly, the lunar feldspathic fragmental breccia comprising the individual stones Dhofar 081, 280, 910, and 1224 was found in the western half of this same strewn field, which encompasses an area of 1.4 x 1.2 km—an astounding case of overlapping lunar strewn fields! Cosmogenic nuclide studies of Dhofar 908 based on 10Be and 26Al have enabled the determination of the excavation depth on the Moon (>6 m), the Moon–Earth transit time (4 ±1 t.y.), and the terrestrial age (~300 t.y.) (Nishiizumi and Caffee, 2006).

Studies of Dhofar 489, a member of the pairing group, revealed the presence of magnesian anorthosite clasts and a spinel troctolite clast, and that its bulk analysis is highly depleted in Th (proxy for ITEs) and FeO (Takeda et al., 2007). In addition, studies of the paired stone Dhofar 309 revealed clasts of anorthosite and troctolite composition, considered to be metamorphosed and annealed crystalline rocks associated with an impact melt pool. In addition, studies of the pairing Dhofar 307 led to the discovery of magnesian granulitic clasts, some of which contain large olivine fragments embedded in a glassy plaagioclase matrix (Takeda et al., 2008). These olivine fragments may represent ejected mantle rock from the massive impact that created the largest impact crater in the Solar System, the South Pole–Aitken basin, on the lunar farside. A reddish orange clast found in these stones has a crystalline texture and contains plagioclase crystals and rounded olivine grains; it is thought to be an impact melt clast derived from spinel troctolite, but which includes a pyroxene component derived from norite. The magnesian anorthosite clasts are devoid of ferroan anorthosite and Mg-suite components, both of which are typical contaminates in lunar breccias recovered from the nearside of the Moon.

Since Dhofar 908 and its pairing group members are an impact-melt breccia which could be formed at a significant depth beneath a regolith potentially contaminated with incompatible elements, its low-Th, low-Fe signature taken by itself is not an adequate determinant for either a nearside or a farside origin for this type of lunar meteorite (R. Korotev). However, when these analyses are considered together, along with the possible discovery of a norite component, it can be inferred that the origin of this pairing group is likely the lunar farside—possibly from the area of the South Pole–Aitken basin, or perhaps in the Feldspathic Highlands Terrane at the northern portion of the lunar farside. The mineralogy, chemistry, and petrology of the various members of this pairing group indicate that they all were derived from a common precursor lithology, one having a spinel troctolite composition and that was located at a significant depth (>5 m) within the crust (Takeda et al., 2008).

The specimen pictured above is a 0.143 g very thin partial slice from the main mass of Dhofar 908. The photo below shows the first mass of Dhofar 908 to be found, weighing 81.43 g, which is the main mass, exported by permit from the Ministry of Commerce and Industry, Sultanate of Oman. The bottom photo is a beautiful 0.61 g thin slice from the Dhofar 908 main mass showing three (or more?) separate lithologies.