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H Y D R O G E N CYANIDE P O L Y M E R S F R O M THE I M P A C T OF C O M E T P / S H O E M A K E R - L E V Y 9 ON

JUPITER

Clifford Matthews, University of Illinois, Chicago, IL 60607, USA; FAX 312-996-0431

Hydrogen cyanide polymers--heterogeneous solids ranging in color from yellow to orange to brown to black--may be among the organic macromolecules most readily formed within the solar system. The non- volatile black crust of comet Halley, for example, as well as the extensive orange-brown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia (Matthews, 1992).

Laboratory studies by Matthews et al. of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to a-amino acids. Other polymers and multimers with ladder structures derived from HCN would also be present, and might well be the source of the many nitrogen heterocycles, adenine included, detected by thermochemolytic analysis of HCN polymers (Minard et al., 1995).

The most notable consequence of the impact of comet P/Shoemaker- Levy 9 on Jupiter was the development of several dark brown rings resulting from the fallback of an initially formed plume onto its atmosphere (Leonard, 1995). The so-called "brown stuff" could have consisted mainly of HCN polymers, whether originally present, deposited by the impactor, or synthesized from freshly formed HCN. Emission from HCN has been detected by mid-IR spectroscopy over all impact sites observed from the NASA Infrared Telescope Facility at Mauna Kea, Hawaii (B6zard et al., 1995, Griffith et al., 1995). It is likely that silicate grains would assist in bringing about condensation of the "brown stuff" and other organic materials containing nitrogen or sulfur (West et al., 1995, Levy et al., 1995).

The collision would naturally disperse polymeric cyanide material and produce compounds such as nitriles, nitrogen heterocycles, polypeptides and amino acids by pyrolysis and hydrolysis reactions. Spectroscopic detection of these predicted macromolecules and their by- products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

B6zard, B. et al.: 1995, Abstr. IAU Colloquium 156: The Collision of Comet P/Shoemaker-Levy 9 and Jupiter, Baltimore, MD, p. 7.

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Griffith, C.A. et al.: Abstr. IAU Colloquium 156: The Collision of Comet P/Shoemaker-Levy 9 and Jupiter, Baltimore, MD, p. 42.

Leonard, P.J.T.: 1995, Nature 375, 358. Matthews, C.N.: 1992, Origins of Life, 21,421. Minard, R.D.: 1996, Abstr. 1 lth International Conference on the

Origin of Life, Orleans, France, July 7-12. West, R.A. et al.: 1995, Science 267, 1296.

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