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Cosmogenic radionuclides in the Sołtmany (L6) meteorite

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Laubenstein M. , Giampaoli A. , Janowski P. , Mietelski J. W.

tom Vol. 2, No. 1-2

45--51

Cosmogenic radionuclides were measured in two specimens of the Sołtmany chondrite (L6) that fell on April 30, 2011. The first fragment (154.9 g) was measured 12 days after the fall and the second piece (120 g), 53 days after the fall. Both fragments were measured by means of non-destructive gamma ray spectroscopy. The first specimen was examined with an ultra-low background high purity germanium (HPGe) detector in a deep underground laboratory. A standard low-background HPGe detector was used to examine the second fragment in a ground level laboratory. Twelve cosmogenic nuclides were detected in the activity range of 0.030 m・Bq g–1 until 1.5 m・Bq g–1 Their activities place constraints on the exposure history of the meteorite and reflect the effect of solar modulation of galactic cosmic rays during the solar maximum. On the activities of expected radionuclides 60 Co (< 0.0075 m・Bq g–1) and 44 Ti (< 0.023 m・Bq g–1) only upper limits could be given. Sołtmany is part of a group of only 14 meteorites where 52 Mn (5.591 d half life) could be determined.

The meteorite fall near Boumdeid, Mauritania, from September 14, 2011

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Buhl S. , Toueirjenne C. , Hofmann B. , Laubenstein M. , Wimmer K.

tom Vol. 3, No. 1-2

5--18

On the evening of September 14, 2011 at 21:00 GMT a bright bolide was observed by hundreds of eyewitnesses in the area north and west of the town of Kiffa, in the department of Assaba, in south Mauritania. A terminal fragmentation and sound phenomena were observed near the end point of the trajectory. At least one mass of 3.5 kg was observed to impact and recovered the morning after the fall near Boumdeid (or Bou Mdeid), around 60 km north of Kiffa. Subsequently a large number of eyewitness accounts were recorded and mapped by GPS. The present paper provides a scenario for the trajectory of the Boumdeid (2011) meteorite based on the available parameters and wind data at the relevant altitudes. In addition the paper presents the results of the mineralogical and chemical analysis of the recovered meteorite which is consistent with a classification as ordinary chondrite of type L6, shock stage S2, and a weathering grade of W0. Following its analysis and classification, the meteorite was published under the official name Boumdeid (2011) in Meteoritical Bulletin, no. 100, MAPS 49(8), (2014). Gamma ray spectroscopy was conducted 84 days after the fall and the detection of short-lived radionuclides such as 56Co and 46Sc confirmed the recency of the event. Derived from the data of 60Co, 54Mn and 22Na the approximate preatmospheric radius of the meteorite body was 10–20cm. The report is also intended to serve as a case example for post-event data recovery and trajectory reconstruction in areas not covered by sky-camera networks and with limited scientific infrastructure.