Extra-Terrestrial Phosphorus and Reduced Forms

Quite a number of different phosphorus compounds have now been detected outside planet earth. Apatite has been found in lunar dust, and methyl phosphonic acid Me-P(0)(0H)2, has been extracted 

FIGURE 2.5 Growth of total world output of mined phosphate ores in the twentieth century. 

The main part of the photolysis of phosphine can be represented by the initial steps (2.1) and (2.2). Further possible reactions leading to the prodnction of elemental phosphorus (e.g. 4.156), have been listed [34]. 

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. 

Phosphorous trioxide, P4O6, is present in the atmosphere of Venus [34]. Spectroscopic molecules such as PH, PO, PN, PC and more recently HC P, have all been detected in interstellar space. Recent studies [36] have supported earlier views [37] that phosphorus may have originally been present on Earth in a reduced oxidation state, for example, as derivatives of phosphonic (phosphorous) acid H3PO3 rather than of phosphoric acid H3PO4. Recent studies have confirmed that condensed phosphates (which are needed for the production of evolutionary DNA) can be produced by oxidation of phosphonates or phosphinates [38]. The identification of sulphate-reducing bacteria (Chapter 11.7), also suggests a means by which P could have become fully oxidised during the course of planetary evolution. Natural phosphine gas, PH3, may also result from bioreduction processes (Chapter 4.4). 

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