• Barbianello: An ungrouped nickel-rich iron meteorite found in Italy

      Fehr, K. T.; Carion, A. (The Meteoritical Society, 2004-01-01)
      An unusual iron was found in 1960 in Barbianello (northern Italy, Pavia municipality) by a farmer, Clemente Allini, ploughing his fields. Years later, the iron was recognized as a meteorite but not officially classified. Our investigations indicate that Barbianello is a unique nickel-rich ataxite with dark and light regions texturally similar to, but compositionally distinct from, Santa Catharina iron. The light regions are chemically homogeneous, have a Ni content of 27.1 wt%, and a composition similar to irons of group IAB-IIICD. The dark regions are inhomogeneous with Ni ranging from 40 to 58 wt% and oxygen up to 20 wt%. Relics of unoxidized metal and textural relationships indicate that, unlike Santa Catharina, the dark regions result from the oxidation of a metal compositionally distinct from that of light regions.
    • Barringer Medal Citation for Graham Ryder

      Spudis, Paul D. (The Meteoritical Society, 2003-01-01)
    • Beni M'hira: A new chondrite (L6) meteorite fall from Tunisia

      Ouazaa, N. L. (The Meteoritical Society, 2004-01-01)
      The Beni M'hira meteorite fell on January 8, 2001 in southeastern Tunisia. This is only the fifth observed fall from Tunisia. On the basis of mineralogical, petrographic, and geochemical data, the stone can be classified as an L6 chondrite of shock stage S5.
    • Bhawad LL6 chondrite: Chemistry, petrology, noble gases, nuclear tracks, and cosmogenic radionuclides

      Bhandari, N.; Murty, S. V. S.; Shukla, P. N.; Mahajan, R. R.; Shukla, A. D.; Suthar, K. M.; Parthasarathy, G.; Paliwal, B. S. (The Meteoritical Society, 2005-01-01)
      Chemical and mineral analysis of the Bhawad chondrite, which fell in Rajasthan in 2002, suggest that this stone belongs to LL6 group of chondrites. Based on helium, neon, and argon isotopes, it has a cosmic ray exposure age of 16.3 Ma. The track density in the olivines shows a narrow range of 1.7-6.8 106/cm2. The 22Na/26Al ratio of 1.13 is about 25% lower than the solar cycle average value of about 1.5, but is consistent with irradiation of the meteoroid to modulated galactic cosmic ray fluxes as expected for a fall around the solar maximum. The cosmogenic records indicate a pre-atmospheric radius of about 7.5 cm. Based on U/Th-4He and K-40Ar, the gas retention ages are low (about 1.1 Ga), indicating a major thermal event or shock event that lead to the complete loss of radiogenic 4He and 40Ar and the partial loss of radiogenic 129Xe and fission Xe from 244Pu.
    • Biological processes in impact craters, King's College, University of Cambridge, U. K., 2003 March 29 to April 1

      The Meteoritical Society, 2002-01-01
      Announcement: Biological processes in impact craters, King's College, University of Cambridge, U. K., 2003 March 29 to April 1
    • Bolides in the present and past martian atmosphere and effects on cratering processes

      Popova, O.; Nemtchinov, I.; Hartmann, W. K. (The Meteoritical Society, 2003-01-01)
      We investigate the action of the martian atmosphere on entering meteoroids for present and past atmospheres with various surface pressures to predict the smallest observable craters, and to understand the implications for the size distributions of craters on Mars and meteoroids in space. We assume different strengths appropriate to icy, stone, and iron bodies and test the results against available data on terrestrial bolides. Deceleration, ablation, and fragmentation effects are included. We find that the smallest icy, stone, and iron meteoroids to hit the martian ground at crater forming speeds of greater than or equal to 500 m/s have diameters of about 2 m, 0.03-0.9 m (depending on strength), and 0.01 m, respectively, in the current atmosphere. For hypothetical denser past atmospheres, the cutoff diameters rise. At a surface pressure of 100 mb, the cutoff diameters are about 24 m, 5-12 m, and 0.14 m for the 3 classes. The weaker stony bodies in the size range of about 1-30 m may explode at altitudes of about 10-20 km above the ground. These figures imply that under the present atmosphere, the smallest craters made by these objects would be as follows: by ice bodies, craters of diameter (D) ~8 m, by stones about 0.5-6 m, and by irons, about 0.3 m. A strong depletion of craters should, thus, occur at diameters below about 0.3 m to 5 m. Predicted fragmentation and ablation effects on weak meteoroids in the present atmosphere may also produce a milder depletion below D ~500 m, relative to the lunar population. But, this effect may be difficult to detect in present data because of additional losses of small craters due to sedimentation, dunes, and other obliteration effects. Craters in strewn fields, caused by meteoroid fragmentation, will be near or below present-day resolution limits, but examples have been found. These phenomena have significant consequences. Under the present atmosphere, the smallest (decimeter-scale) craters in sands and soils could be quickly obliterated but might still be preserved on rock surfaces, as noted by Horz et al. (1999). Ancient crater populations, if preserved, could yield diagnostic signatures of earlier atmospheric conditions. Surfaces formed under past denser atmospheres (few hundred mbar), if preserved by burial and later exposed by exhumation, could show: a) striking depletions of small craters (few meter sizes up to as much as 200 m), relative to modern surfaces; b) more clustered craters due to atmospheric breakup; and degrees C) different distributions of meteorite types, with 4 m to 200 m craters formed primarily by irons instead of by stones as on present-day Mars. Megaregolith gardening of the early crust would be significant but coarser than the gardening of the ancient lunar uplands.
    • Boltysh, another end-Cretaceous impact

      Kelley, S. P.; Gurov, E. (The Meteoritical Society, 2002-01-01)
      The Chixculub impact occurred at the Cretaceous/Tertiary (K/T) boundary, and although several other Late Cretaceous and Paleogene impact craters have, at times, been linked with the K/T boundary, isotope geochronology has demonstrated that all have significantly different ages. The currently accepted age of the 24 km diameter Boltysh crater, a K-Ar whole-rock age, places it in the Coniacian at 88 +/- 3 Ma. However, comprehensive Ar-Ar dating of a range of melt samples yields a mean age of 65.17 +/- 0.64 Ma, within errors of the K/T boundary. Several of the fresh samples exhibit signs of excess argon, but this seems to be concentrated in rapidly crystallized glass-rich samples. The Ar-Ar age confirms an earlier fission track measurement and thus two dating techniques have yielded an age within errors of the K/T boundary for this crater. Crucially, although the ages of Boltysh and Chixculub are within errors, they may not have formed synchronously. Craters of 24 km diameter occur much more commonly than impacts of Chixculub dimensions, but their proximity does raise the important question of how many impacts there might have been close to the K/T boundary.
    • Book Review: A Traveler's Guide to Mars, William K. Hartmann

      Baier, A. P. (The Meteoritical Society, 2003-01-01)
    • Book Review: Astrobiology, Monica Grady

      Brewer, J. (The Meteoritical Society, 2002-01-01)
    • Book Review: Basics of the Solar Wind, Nicole Meyer-Vernet

      Lal, D. (The Meteoritical Society, 2008-01-01)
    • Book Review: Cassini at Saturn: Huygens Results, David M. Harland

      Barnes, J. W. (The Meteoritical Society, 2008-01-01)