Production of organic molecules by proton irradiation
An energy source worthy of consideration for the production of organic molecules in primitive planetary atmospheres is stated to be energetic protons in the solar wind and in planetary radiation belts. The satellites of the outer planets are exposed to the solar wind, and two of these, Io and Titan, are unusually red; Titan is especially interesting as it is known to possess an atmosphere containing H/sub 2/ and CH/sub 4/. Protons can also bombard a planetary atmosphere directly from discharges in the radiation belts. Experimental work is described which was carried out to investigate the effectiveness of proton irradiation for producing organic chromophores; 2-MeV protons from a tandem Van de Graaff machine were used for the irradiations, and the beams employed ranged from 870 down to 220 nA. Based on the nominal model for the flux in Jupiter's radiation belt at six Jupiter radii from the planet (approximately the distance of Io) these beams correspond to 1.72 and 0.43 earth years at Jupiter per second of exposure. Five gas mixtures were used in the experiments, none of which contained water. The first irradiation cell, exposed to 870 nA for 3 hr, contained CH/sub 4/ and NH/sub 3/, and high resolution mass spectrometry of the gas phase indicated the presence of C/sub 2/H/sub 2/, C/sub 2/ H/sub 4/, and C/sub 2/H/sub 6/ plus their methyl homologues, as well as C/sub 4/H/ sub 2/, CH/s ub a/CN, and residual CH/sub 4/ and NH/sub 3/. The brown oily liquid produced was analyzed by computer-assisted gas chromatography--mass spectrometry, which indicated the presence of the expected alkyl hydrocarbons and alkylamines. Some unexpected and interesting products included tricyclic alkylamines, hexamethylene tetramine and its methyl and dimethyl homologues. In the second experiment, the total dose was reduced by half. In this case, lower molecular weight molecules were enriched relative to those of higher molech/sub 3/ , and H/sub 2/S was used: the gas phase contained several simple hydrocarbons saturated and unsaturated, with some CH/sub 3/CN and (CH/sub 3/)/sub 2/S. The ga s chromatogram of the liquid formed indicated the presence of a series of alkyl di- and tri-suifides, starting with (CH/sub 3/)/sub 2/S/sub 3/an d increasing in alkyl chain length; its yellow color was found to be due to free polymeric S. This result was very interesting, since S and ammonium polysulfides have been proposed to account for the yellow color on Jupiter. In experiment four a mixture of CH/sub 4/ and N/sub 2/ was used; the gas phase contained the same species as in the case of CH/sub 4/ and NH/sub 3/, but the liquid contained a much larger proportion of alkylamines relative to cyclic amines. The last cell contained only CH/sub 4/ and was run as a check on possible contributions of impurities in the apparatus to the irradiation products. It was obvious from the results that energetic protons can be an effective energy source for the formation of complex molecules from simple molecules. The presence of N or S seems to be necessary for the formation of colored products. (UK)
- Research Organization:
- State Univ. of New York, Stony Brook
- NSA Number:
- NSA-29-019305
- OSTI ID:
- 4313694
- Journal Information:
- Nature (London), v. 247, no. 5436, pp. 100-101, Other Information: Orig. Receipt Date: 30-JUN-74; Bib. Info. Source: UK (United Kingdom (sent to DOE from))
- Country of Publication:
- United Kingdom
- Language:
- English
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Related Subjects
N40300 -Chemistry-Radiation Chemistry
*JUPITER PLANET- CHEMICAL COMPOSITION
*PLANETARY ATMOSPHERES- CHEMICAL COMPOSITION
*PROTON BEAMS- RADIOLYSIS
AMMONIA
COLOR
COLORATION
HYDROGEN
HYDROGEN SULFIDES
METHANE
NITROGEN
ORGANIC COMPOUNDS
RADIATION BELTS
SOLAR WIND