Oudiyat Sbaa        25.546°N, 12.418°W

Western Sahara/Morocco

Confirmed fall: 2016 Nov 18

Classification: Enstatite chondrite (EH5)

History: On November 18, 2016, at 4:40 pm local time, a bright fireball was witnessed traveling in a southerly direction by many observers in Morocco over an area extending from Tiznit to Guelmim, Tan Tan and Smara. Sonic booms were heard by Mbarek Bouilid, Aitoussi Redwan and three camel shepherds of the Aitboussoula family (who thought that perhaps the sound was caused by explosion of a mine trodden on by a camel). A search for fallen stones was begun, and on November 23 another shepherd (Bachir Alamine) found three black fusion-crusted stones on light brown sandy soil near Oudiyat Sbaa.

Physical characteristics: The stones are completely coated in thin, black fusion crust. The fresh interiors are overall medium gray in color with abundant shiny grains of metal and sulfides. When first found the stones emitted a sulfurous odor.

Petrography: (A. Irving and S. Kuehner, UWS) Some well-formed chondrules (apparent diameter 300±100 μm) are present within a recrystallized matrix containing abundant metal and sulfides. Apart from dominant enstatite, the specimen contains alkali feldspar, Si-bearing kamacite, niningerite, oldhamite, Cr-bearing troilite and schreibersite. A spherical crystalline object (apparent diameter 1.1 mm) observed in one thin section is composed predominantly of fluororichterite associated with a silica polymorph, enstatite and sulfides.

Geochemistry: Enstatite (Fs_0.4-0.6Wo_0.1-0.3, N = 3), alkali feldspar (Ab_88.7-93.1An_1.1-0.9Or_10.2-6.0, N = 2), metal (Ni 6.2-6.3 wt.%, Co 0.4 wt.%, Si 3.3 wt.%, N = 2). Cosmogenic radionuclides: (Å. Rosén, UBE/NMBE, GeMSE): Gamma-spectroscopy performed in February 2017 showed the presence of the following cosmogenic radionuclides: ⁴⁶Sc, ⁵⁶Co, ⁵⁴Mn, ⁵⁸Co, ⁷Be, ⁴⁸V, ⁵¹Cr, ⁵⁷Co, ²²Na, ⁴⁴Ti and ²⁶Al. Recalculated to 18 November 2016 and assuming average EH chondrite density and composition, ⁴⁸V was 43.0 (+7.8,-5.2), ²²Na was 60.8 (+8.1,-4.6) dpm/kg and ²⁶Al 53.6 (+7.9,-3.4) dpm/kg. The ²²Na/²⁶Al activity ratio of 1.1 (+0.2,-0.1) and detected activity of ⁴⁸V (t_1/2=16 d) are consistent with a fall in November 2016. Magnetic susceptibility log χ (× 10^-9 m³/kg) = 5.74.

Classification: Enstatite chondrite (EH5).

Specimens: 173.7 g including one polished thin section and a polished thick section at UWB; 17.3 g plus one polished thin section at NMBE; remainder with DPitt.