Thika        1°0.167’S, 37°9.017’E

Kiambu County, Kenya

Fell: 16 July 2011

Classification: Ordinary chondrite (L6)

History: A bright fireball in multiple pieces was observed from southern Kenya traveling to the northwest around 10 am on the July 16, 2011. Residents around Kiambu County in the Thika District reported multiple loud explosions and loud screaming noises, with ground shaking. The first piece (~2.5 kg) landed within 1 m of a woman tilling her field in the village of Kihum Wiri (also spelled Kiumwiri). This meteorite was subsequently removed by the military and taken to the University of Nairobi. Multiple pieces were then found in the nearby village of Mwana Wikio. Two meteorites smashed through greenhouses in Mwana Wikio and one through a house in nearby Muguga village. Stones were recovered from a 7.7 × 1.6 km strewnfield bearing N30°W. The main mass, 3.575 kg, was found outside Rose Kamande’s house in Kihum Wiri the day after the fall. Total known mass is currently 14.2 kg totaling 14 individuals, distributed primarily as large stones, e.g., 3575 g, ~2.5 kg, 1.75 kg and 1.3 kg. Only a few small stones have so far been recovered. All stones were recovered before rainfall.

Physical characteristics: Stones are angular and fusion crusted. Interior of the fresh stones is white.

Petrography: Shock stage S1 and weathering W0. One thin shock vein is present in the section, otherwise none are recognizable in the stones. The sections show poorly defined chondrules in a recrystallized matrix. Recognizable chondrules (to 1.6 mm) include BO, RP, and POP. Common accessory minerals include chlorapatite, merrillite, and Ti-rich chromite, and rare ilmenite. Merrillite is particularly abundant with ~50 grains larger than 100 microns on the one-inch-round thin section. Largest merrillite is 600 microns across. Much of the metal and sulfide occurs as separate, blocky grains.

Geochemistry: (Laurence Garvie, ASU) Microprobe analyses show olivine, Fa_24.5±0.3 (n=11) and FeO/MnO=50.0 (n=11), pyroxene Fs_20.5±0.3Wo_1.6±0.5 (n=9), and diopside Fs_7.7-8.1Wo_45.0 (n=2). Representative analysis of chlorapatite (normalized to three P atoms) is Ca_4.93Fe_0.02(PO₄)₃Cl_0.71F_0.26 and merrillite (normalized to seven P atoms) is Ca_8.9Na_0.8Mg_0.8Fe_0.3(PO₄)₇.

Classification: Ordinary chondrite, L6, S1, W0.

Specimens: ASU holds a 377 g stone (70% fusion crusted), 29.82 g in six pieces, and two thin sections. MFarmer holds the 3.575 kg mass and another 3 kg.