T.J. Zega H. Yano S. Wirick A.J. Westphal M.K. Weisberg I. Weber J.L. Warren M.A. Velbel A. Tsuchiyama P. Tsou A. Toppani N. Tomioka K. Tomeoka N. Teslich M. Taheri J. Susini R. Stroud T. Stephan F.J. Stadermann C.J. Snead S.B. Simon A. Simionovici T.H. See F. Robert F.J.M. Rietmeijer W. Rao M.C. Perronnet D.A. Papanastassiou K. Okudaira K. Ohsumi I. Ohnishi K. Nakamura-Messenger T. Nakamura S. Mostefaoui T. Mikouchi A. Meibom G. Matrajt M.A. Marcus H. Leroux L. Lemelle L. Le A. Lanzirotti F. Langenhorst A.N. Krot L.P. Keller A.T. Kearsley D. Joswiak D. Jacob H. Ishii R. Harvey K. Hagiya L. Grossman J.H. Grossman G.A. Graham M. Gounalle P. Gillet M.J. Genge G. Flynn T. Ferroir S. Fallon D.S. Ebel Z.R. Dai P. Cordier B. Clark M. Chi Anna L. Butterworth D.E. Brownlee J.C. Bridges S. Brennan A. Brearley J.P. Bradley P. Bleuet P.A. Bland R. Bastien M.E. Zolensky 2006 The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk. application/pdf 10.1126/science.1135842 en Mineralogy and petrology of comet 81P/wild 2 nucleus samples article