High impact information on Meteoroids

• The chondrites define a Lu-Hf isochron with an initial 176Hf/177Hf ratio of 0.279628 +/- 0.000047, corresponding to lambda176Lu = 1.983 +/- 0.033 x 10-11 yr-1 using an age of 4.56 Gyr for the chondrite-forming event [1].
• The tungsten isotope composition of meteorites indicates that core formation in planetesimals occurred within a few million years of Solar System formation [2].
• Early history of Earth's crust-mantle system inferred from hafnium isotopes in chondrites [1].
• But material from the Earth, Mars, comets and various meteorites have Mg/Si and Al/Si ratios, oxygen-isotope ratios, osmium-isotope ratios and D/H, Ar/H2O and Kr/Xe ratios such that no primitive material similar to the Earth's mantle is currently represented in our meteorite collections [3].
• Diverse supernova sources of pre-solar material inferred from molybdenum isotopes in meteorites [4].

Associations of Meteoroids with chemical compounds

• Here we find that K/T boundary sediments at Stevns Klint, Denmark, contain both alpha-amino-isobutyric acid [AIB,(CH3)2CNH2COOH] and racemic isovaline [ISOVAL, CH3CH2(CH3)CNH2COOH], two amino acids that are exceedingly rare on the Earth but which are major amino acids in carbonaceous chondrites [5].
• Here we report measurements of tungsten isotope compositions and hafnium-tungsten ratios of several meteorites [6].
• On Venus, the absolute abundances of neon and argon per gram of rock are higher even than those in carbonaceous chondrites, whereas the relative abundances of argon and krypton are closer to solar than to chondritic values (there is only an upper limit on xenon) [7].
• 16O excesses in olivine inclusions in Yamato-86009 and Murchison chondrites and their relation to CAIs [8].
• Accretion models of the terrestrial planets often assume planetary bulk compositions with nonvolatile element abundance ratios equivalent to those of C1 carbonaceous chondrites [9].

Gene context of Meteoroids

• Rapid accretion and early differentiation of Mars indicated by 142Nd/144Nd in SNC meteorites [10].
• AOX concentrations varying from 124 to 209 microg Cl/g d.w. were observed in carbonaceous meteorites [11].
• The relatively (compared to glycine) high AIB content found in all the CMs is a strong indicator that Strecker-cyanohydrin synthesis is the dominant pathway for the formation of amino acids found in these meteorites [12].
• [Stoffler, D., Keil, K., Scott, E.R.D., 1991. Shock metamorphism of ordinary chondrites. Geochim. Cosmochim. Acta 55, 3845-3867] [13].
• The primitive matrix components of the unique carbonaceous chondrite Acfer 094: a TEM study [14].

References