Sutter's Mill - 22.04.2012 - Bolide über USA California/Nevada

[karmaka]

Exposure history of the Sutter's Mill carbonaceous chondrite

Nishiizumi K, Caffee MW, Hamajima Y, Reedy RC and Welten KC

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The Sutter's Mill (SM) carbonaceous chondrite fell in California on April 22, 2012. The cosmogenic radionuclide data indicate that Sutter's Mill was exposed to cosmic rays for 0.082 ± 0.008 Myr, which is one of the shortest ages for C chondrites, but overlaps with a small cluster at approximately 0.1 Myr. The age is significantly longer than proposed ages that were obtained from cosmogenic noble gas concentrations, which have large uncertainties due to trapped noble gas corrections. The presence of neutron-capture 60Co and 36Cl in SM indicates a minimum preatmospheric radius of approximately 50 cm, and is consistent with a radius of 1–2 m, as derived from the fireball observations. Although a large preatmospheric size was proposed, one fragment (SM18) contains solar cosmic ray–produced short-lived radionuclides, such as 56Co and 51Cr. This implies that this specimen was less than 2 cm from the preatmospheric surface of Sutter's Mill. Although this conclusion seems surprising, it is consistent with the observation that the meteoroid fragmented high in the atmosphere. The presence of SCR-produced nuclides is consistent with the high SCR fluxes observed during the last few months before the meteorite's fall, when its orbit was less than 1 AU from the Sun.

Sutter's Mill #18
5.4 g
Fundort: 38.8125 N, 120.9056 W   
gefunden von Gregory Jorgensen am 2.5.2012

Der UC Davis wurde von Gregory Jorgensen ein Sutter's Mill Exemplar gespendet.
Es wird sich hierbei wohl um SM 17 (7,2 g) handeln:

http://www.news.ucdavis.edu/search/news_detail.lasso?id=10246

Oder vielleicht doch SM18 ... eine Schenkung trägt Früchte! 

[karmaka]

Presolar grains in the CM2 chondrite Sutter’s Mill

Zhao X, Lin Y, Yin Q-Z, Zhang J, Hao J, Zolensky M and Jenniskens P

Meteoritics & Planetary Science. doi: 10.1111/maps.12289, (published online: 30 JUN 2014)

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The Sutter's Mill (SM) carbonaceous chondrite is a regolith breccia, composed predominantly of CM2 clasts with varying degrees of aqueous alteration and thermal metamorphism. An investigation of presolar grains in four Sutter's Mill sections, SM43, SM51, SM2-4, and SM18, was carried out using NanoSIMS ion mapping technique. A total of 37 C-anomalous grains and one O-anomalous grain have been identified, indicating an abundance of 63 ppm for presolar C-anomalous grains and 2 ppm for presolar oxides. Thirty-one silicon carbide (SiC), five carbonaceous grains, and one Al-oxide (Al2O3) were confirmed based on their elemental compositions determined by C-N-Si and O-Si-Mg-Al isotopic measurements. The overall abundance of SiC grains in Sutter's Mill (55 ppm) is consistent with those in other CM chondrites. The absence of presolar silicates in Sutter's Mill suggests that they were destroyed by aqueous alteration on the parent asteroid. Furthermore, SM2-4 shows heterogeneous distributions of presolar SiC grains (12–54 ppm) in different matrix areas, indicating that the fine-grained matrix clasts come from different sources, with various thermal histories, in the solar nebula.

[karmaka]

Als 'nachurlaubiger Nachtrag':

53Mn-53Cr dating of aqueously formed carbonates in the CM2 lithology of the Sutter's Mill carbonaceous chondrite

Christine E. Jilly, Gary R. Huss, Alexander N. Krot, Kazuhide Nagashima, Qing-Zhu Yin and Naoji Sugiura

Meteoritics & Planetary Science, DOI: 10.1111/maps.12305, Article first published online: 7 AUG 2014

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Abstract

Radiometric dating of secondary minerals can be used to constrain the timing of aqueous alteration on meteoritic parent bodies. Dolomite is a well-documented secondary mineral in CM chondrites, and is thought to have formed by precipitation from an aqueous fluid on the CM parent body within several million years of accretion. The petrographic context of crosscutting dolomite veins indicates that aqueous alteration occurred in situ, rather than in the nebular setting. Here, we present 53Mn-53Cr systematics for dolomite grains in Sutter's Mill section SM51-1. The Mn-Cr isotope data show well-resolved excesses of 53Cr correlated with 55Mn/52Cr ratio, which we interpret as evidence for the in situ decay of radioactive 53Mn. After correcting for the relative sensitivities of Mn and Cr using a synthetic Mn- and Cr-bearing calcite standard, the data yield an isochron with slope corresponding to an initial 53Mn/55Mn ratio of 3.42 ± 0.86 × 10−6. The reported error includes systematic uncertainty from the relative sensitivity factor. When calculated relative to the U-corrected Pb-Pb absolute age of the D'Orbigny angrite, Sutter's Mill dolomites give a formation age between 4564.8 and 4562.2 Ma (2.4–5.0 Myr after the birth of the solar system). This age is contemporaneous with previously reported ages for secondary carbonates in CM and CI chondrites. Consistent carbonate precipitation ages between the carbonaceous chondrite groups suggest that aqueous alteration was a common process during the early stages of parent body formation, probably occurring via heating from internal 26Al decay. The high-precision isochron for Sutter's Mill dolomite indicates that late-stage processing did not reach temperatures that were high enough to further disturb the Mn-Cr isochron.

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Neues vom kleinen Schwarzen:

Diamond xenolith and matrix organic matter in the Sutter's Mill meteorite measured by C-XANES

Yoko Kebukawa, Michael E. Zolensky, A. L. David Kilcoyne, Zia Rahman, Peter Jenniskens and George D. Cody

Meteoritics & Planetary Science. doi: 10.1111/maps.12312
Article first published online: 13 OCT 2014

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Infrared imaging spectroscopy with micron resolution of Sutter's Mill meteorite grains

Mehmet Yesiltas, Yoko Kebukawa, Robert E. Peale, Eric Mattson, Carol J. Hirschmugl and Peter Jenniskens

Meteoritics & Planetary Science
Article first published online: 13 OCT 2014 | DOI: 10.1111/maps.12321

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Chromium isotopic systematics of the Sutter's Mill carbonaceous chondrite: Implications for isotopic heterogeneities of the early solar system

Akane Yamakawa and Qing-Zhu Yin

Meteoritics & Planetary Science
Article first published online: 13 OCT 2014 | DOI: 10.1111/maps.12346

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[karmaka]

Spannend!

Discovery of primitive CO2-bearing fluid in an aqueously altered carbonaceous chondrite 

Akira Tsuchiyama, Akira Miyake, Satoshi Okuzumi, Akira Kitayama, Jun Kawano, Kentaro Uesugi, Akihisa Takeuchi, Tsukasa Nakano, Michael Zolensky

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