Noble gas contents of shergottites and implications for the Martian origin of SNC meteorites
作者： D.D. Bogard , L.E. Nyquist , P. Johnson
DOI: 10.1016/0016-7037(84)90028-0
关键词: Krypton 、 Nakhlite 、 Achondrite 、 Atmosphere of Mars 、 Martian 、 Astrobiology 、 Meteorite 、 EETA 79001 、 Geology 、 Mars Exploration Program
摘要: Abstract Isotopic concentrations of the noble gases have been measured in several different phases Elephant Moraine A79001 and whole rock samples Zagami Allan Hills A77005, three meteorites which belong to rare group SNC achondrites that may originated from planet Mars. Shocked EETA79001 contain a trapped Ar, Kr, Xe component characterized by 84 Kr 132 ∼15, 40 Ar 36 > 2000 , 129 ≥ 2 4 He ≤ 0.1 . These elemental isotopic ratios are unlike those for any other gas except analyses Martian atmosphere made Viking spacecraft. The composition shows an approximate 1% per mass unit enrichment lighter isotopes compared terrestrial traped show either fission or fractionated heavier Xe. It is hypothesized these represent portion was shock-implanted into EETA79001, they constitute direct evidence origin shergottite meteorites. Cosmic ray-produced eight known form distinct groups with exposure ages ∼11 MY (Chassigny nakhlites), ∼2.6 (Shergotty, Zagami, ALHA77005), ∼0.5 (EETA79001). suggest events cannot produced irradiation common time under greatly shielding. Comparison cosmogenic 3 21 Ne two independent models production this ratio as function shielding indicates meteorite irradiated space relatively small object. If were ejected Mars ∼ 180 My ago, shock age shergottites, must large objects (>6 meters diameter) experienced at least collisions initiate cosmic ray exposure. Ejection times initiation would permit much smaller (
harvard.edu
jaxa.jp
elsevier.com参考文章(52)
R. C. Reedy, K. Marti, J. R. Shirck, F. A. Podosek, C. M. Hohenberg, Comparisons between observed and predicted cosmogenic noble gases in lunar samples Lunar and Planetary Science Conference Proceedings. ,vol. 2, pp. 2311- 2344 ,(1978)
Lewis D. Ashwal, Charles A. Wood, SNC meteorites: Igneous rocks from Mars? LPSC. ,vol. 12, pp. 1359- 1375 ,(1982)
M. Moergeli, H. Schwaller, N. Groegler, U. Kraehenbuehl, H. Graf, H.R. von Gunten, Mendia, P. Eberhardt, J. Geiss, A. Stettler, TRAPPED SOLAR WIND NOBLE GASES IN APOLLO 12 LUNAR FINES 12001 AND APOLLO 11 BRECCIA 10046. Geochim. Cosmochim. Acta, v. Suppl. 3, pp. 1821-1856. ,vol. 3, pp. 1821- 1856 ,(1972)
G.W. Wetherill, Orbital evolution of impact ejecta from Mars. Meteoritics. ,vol. 19, pp. 1- 13 ,(1984) , 10.1111/J.1945-5100.1984.TB00829.X
O Müller, W Hampel, T Kirsten, G.F Herzog, Cosmic-ray constancy and cosmogenic production rates in short-lived chondrites Geochimica et Cosmochimica Acta. ,vol. 45, pp. 447- 460 ,(1981) , 10.1016/0016-7037(81)90253-2
D.D Bogard, P.J Cressy, Spallation production of 3He, 21Ne, and 38Ar from target elements in the Bruderheim chondrite Geochimica et Cosmochimica Acta. ,vol. 37, pp. 527- 546 ,(1973) , 10.1016/0016-7037(73)90216-0
R. J. Wright, L. A. Simms, M. A. Reynolds, D. D. Bogard, Depth variation of cosmogenic noble gases in the ∼120-kg Keyes chondrite Journal of Geophysical Research. ,vol. 78, pp. 1308- 1318 ,(1973) , 10.1029/JB078I008P01308
D. A. Papanastassiou, G. J. Wasserburg, Evidence for late formation and young metamorphism in the Achondrite Nakhla Geophysical Research Letters. ,vol. 1, pp. 23- 26 ,(1974) , 10.1029/GL001I001P00023
C.-Y. Shih, L.E. Nyquist, D.D. Bogard, G.A. McKay, J.L. Wooden, B.M. Bansal, H. Wiesmann, Chronology and petrogenesis of young achondrites, Shergotty, Zagami, and ALHA77005 - Late magmatism on a geologically active planet Geochimica et Cosmochimica Acta. ,vol. 46, pp. 2323- 2344 ,(1982) , 10.1016/0016-7037(82)90205-8
L.E. Nyquist, J. Wooden, B. Bansal, H. Wiesmann, G. McKay, D.D. Bogard, Rb-Sr age of the Shergotty achondrite and implications for metamorphic resetting of isochron ages Geochimica et Cosmochimica Acta. ,vol. 43, pp. 1057- 1074 ,(1979) , 10.1016/0016-7037(79)90094-2