Meteorite phosphide

Phosphorus is the eleventh element in order of abundance in crustal rocks of the earth and it occurs there to the extent of 1120 ppm (cf. H 1520 ppm, Mn 1060 ppm). All its known terrestrial minerals are orthophosphates though the reduced phosphide mineral schrieber-site (Fe,Ni)3P occurs in most iron meteorites. Some 200 crystalline phosphate minerals have been described, but by far the major amount of P occurs in a single mineral family, the apatites, and these are the only ones of industrial importance, the others being rare curiosities. Apatites (p. 523) have the idealized general formula 3Ca3(P04)2.CaX2, that is Caio(P04)6X2, and common members are fluorapatite Ca5(P04)3p, chloroapatite Ca5(P04)3Cl, and hydroxyapatite Ca5(P04)3(0H). In addition, there are vast deposits of amorphous phosphate rock, phosphorite, which approximates in composition to fluoroapatite. " These deposits are widely... 

Pasek and Lauretta (University of Arizona, Tucson) point to a further important source of phosphate they studied the corrosion of phosphide minerals from iron meteorites under various conditions in aqueous solution, e.g., using NaHCCb as a buffer, or in solutions containing MgCh and CaCL, as well as in the presence of ethanol and acetic acid. 

H. A. Rowland,2 and M. N. Saha could find no evidence in the solar spectrum of the existence of phosphorus in the sun but phosphorus of extra-terrestrial origin has been found in meteorites. 0. C. Farrington reported the occurrence of free phosphorus in the meteorite which fell in Saline Township. Iron phosphide, and iron nickel phosphide have been found in numerous meteorites 3—vide infra, iron phosphide, and schreibersite, and rhabdite. 

E. Hussak, G. Florence, J. A. Antipoff, G. P. Merrill, W. Tassin, etc. H. E. Torne-bohm reported schreibersite in the terrestrial iron of Ovifak, although E. Cohen could not find it there G. vom Rath reported rhabdite in some pig-iron. A. Faye, E. Jannettaz, J. Gamier, and A. Daubree discussed the synthesis of these phosphides. E. Mallard identified the iron phosphide he obtained as the result of a coal-mine fire —vide supra—with rhabdite. G. Tschermak, J. L. Smith, E. Cohen, and E. Cohen and E. Weinschenk showed that dyslytite, schreibersite, and rhabdite are probably the same thing indeed, G. Tschermak found transition forms between acicular and foliated crystals—i.e. between schreibersite and rhabdite—in the meteorite of Braunau. 

Phosphorus is abundant on Earth, both as an element (the llth-most abundant atom in Earth s crust) and as phosphate. Meteorites hold a variety of phosphate-containing minerals and some phosphide minerals.10 Scientists at the University of Arizona have recently suggested that Fe3P, the mineral schreibersite, leads to the formation of phosphate and phosphite when corroded in water. Although phosphorylation of alcohols was not demonstrated, mechanistic considerations suggest that it should be possible. It is noteworthy that a clear prebiotic pathway for the chemical incorporation of phosphate into RNA or DNA has not been found. No nucleosides (nucleobases joined to sugars) have been reported from meteorites. Nor has evidence been found in any meteorite of the presence of nucleosides or nucleotides (nucleosides attached to phosphates). That suggests that nucleic acids were first formed as products of metabolism. 

Rhabdite is a crystalline phosphide of iron approximating in composition to (Ni, Fe)3P. It is found in meteorites in the form of minute tetragonal prisms.7 Density 6-3 to 6 8. 

The approximately 50 known classes of meteorite, excluding those known to have originated from the Moon or Mars, span a wide range of compositions. Most meteorites are stones. The remaining classes of meteorites, the irons and the stony-irons, are products of melting and differentiation. They consist mainly of metallic iron-nickel alloys, sulfides, carbides, phosphides, and igneous silicates. (See the chapter by M. Lipschutz in this volume). 

Schreibesite, (Fe,Ni)3P, and Florenskyite, FeTiP, have been detected in meteorites and in lunar samples [35]. These constitute rare examples of naturally occurring reduced phosphate minerals, and phosphides of this type may be present in the earth s core. 

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