"Rock of the Month # 216, posted June 2019" ---

The Saricicek meteorite from Turkey, a fall on 02 September 2015, of total known weight 15.24 kg. The evening fireball event and meteorite shower around the village of Saricicek in Bingol province, southeast Turkey, brought in its wake a flock of opportunistic meteorite hunters. There was some good fortune for local finders, but also a disruption of normal life, with some of the newcomers even hunting at night with flashlights (Bilgic, 2015: note from Bloomberg in Toronto Star). Saricicek is an example of a howardite, identified as a class of regolith breccias from the asteroid 4 Vesta. This is a nice sawn slice through a cm-scale individual. Note the shiny fusion crust on the outer surface, typical of so many freshly-fallen, feldspathic achondrites.

The howardites are polymict regolith breccias, that contain fragments of associated meteorite classes (igneous rock types) eucrite ("gabbro") and diogenite ("pyroxenite"). They often contain abundant glass, evidence of rapid quenching, generally taken to have occurred immediately following impact events on the Vestan surface.

Howardites may be mixtures of different types of eucrite and diogenite, plus – in the case of paired howardites EET 87503 and EET 87513 - 3% CM2 carbonaceous chondrite material (Buchanan and Mittlefehldt, 2003). The occurrence of relatively primitive and delicate carbonaceous chondrite clasts in howardites is not that rare: note the mm-scale angular black clasts in this month's specimen. Such clasts are noted also in Bholgati (Buchanan et al., 1993). Bholgati, a fall in Orissa state of eastern India in 1905, contains eucrite and CM2 clasts (Laul, 1990; Reid et al., 1990). Another example of a polymict howardite with small black clasts is the 2014 find, NWA 8736. A study of Y793497, Jodzie and Kapoeta revealed 71 carbonaceous chondritic microclasts averaging 0.15 mm in size. Half of the microclasts are rich in tochilinite, and have been termed CM2 material. The remainder are magnetite rich, CR2 (?) microclasts. These tiny bodies could be micrometeorites trapped in the regolith of Vesta at an early stage of solar system evolution (Gounelle et al., 2003). Similar clasts, generally <1 mm in size, occur also in the Erevan howardite (Nazarov et al., 1993; Sahijpal et al., 1994, 1995)

The Dawn space mission to Vesta and Ceres, which launched on 27 September 2007, returned substantial remote-sensing data on these large asteroids (some prefer the term dwarf planet for Ceres). Dawn generated a mass of information (e.g., McSween et al., 2013). The inferred Vestan origins of the HED clan are covered in popular articles by Mayne (2013) and Shanos (2013). In a new analysis of Saricicek and its origins, Unsalan et al. (2019) note that this shower of 343 known stones is the first howardite fall to be documented to modern standards. A plausible source of the HED clan of meteorites is shown to be the Antonia crater, in the Rheasilvia impact basin on Vesta, formed in an impact on the asteroid some 22 million years in the past. Traces of carbonaceous matter in the meteorite offer indications of the nature of the impactor in this event (Yesiltas et al., 2019).

Meteoritical Bulletin, updated to 15 December 2019, lists 375 howardites, of which just 17 are falls. Besides the recently-arrived Saricicek, most are relatively old falls, in that they fell between 1803 and 1942, except for Molteno (1953) and Lohawat (1994).

References

Bilgic,T (2015) Meteor brings wealth and outsiders to Turkish town. Toronto Star, A20, 21 November.

Buchanan,PC and Mittlefehldt,DW (2003) Lithic components in the paired howardites EET 87503 and EET 87513: characterization of the regolith of 4 Vesta. Antarctic Meteorite Research 16, 128- 151, NIPR, Tokyo.

Buchanan,PC, Zolensky,ME and Reid,AM (1993) Carbonaceous chondrite clasts in the howardites Bholgati and EET87513. Meteoritics 28, 659- 669.

Gounelle,M, Zolensky,ME, Liou,J C, Bland,PA and Alard,O (2003) Mineralogy of carbonaceous chondritic microclasts in howardites: identification of C2 fossil micrometeorites. Geochimica et Cosmochimica Acta 67, 507- 527.

Laul,J C (1990) The Bholgati (howardite) consortium: an overview. Geochimica et Cosmochimica Acta 54, 2155- 2159.

Mayne,R (2013) Vesta's children: howardites, eucrites, and diogenites. Meteorite 19 no.1, 17- 21, March.

McSween,HY plus 11, with the Dawn Science Team (2013) Dawn: the Vesta HED connection: and the geologic context for eucrites, diogenites, and howardites. Meteoritics & Planetary Science 48, 2090- 2104.

Nazarov,MA, Brandstatter,F and Kurat,G (1993) Carbonaceous xenoliths from the Erevan howardite. Lunar and Planetary Science 24, 1053- 1054.

Reid,AM, Buchanan,P, Zolensky,ME and Barrett,RA (1990) The Bholgati howardite: petrography and mineral chemistry. Geochimica et Cosmochimica Acta 54, 2161- 2166.

Sahijpal,S, Nazarov,MA and Goswami,JN (1994) Ion microprobe studies of a carbonaceous (CM) xenolith in the Erevan howardite. Meteoritics 29, 526- 527.

Sahijpal,S, Nazarov,MA and Goswami,JN (1995) Sulfur isotopic studies of a P-rich sulfide in a carbonaceous xenolith from the Erevan howardite. Lunar and Planetary Science 26, 1584pp., 1213- 1214.

Shanos,GT (2013) A new Dawn - asteroid Vesta and the HED association confirmed. Meteorite 19 no.1, 5- 11, March.

Unsalan,O, Jenniskens,P plus 77 (the Saricicek Meteorite Consortium) (2019) The Saricicek howardite fall in Turkey: source crater of HED meteorites on Vesta and impact risk of Vestoids. Meteoritics & Planetary Science 54, 953-1008.

Yesiltas,M, Glotch,TD, Jaret,S, Verchovsky,AB and Greenwood,RC (2019) Carbonaceous matter in the Saricicek meteorite. Meteoritics & Planetary Science 54, 1495-1511.