Brief mention may be made of another theory of the nature of the Martian polar caps. It will be recalled from chapter V that, in 1960, C. C. Kiess and his associates had put forward the idea that the Martian atmosphere contains significant quantities of nitrogen dioxide (NO.,) gas. Molecules of this gas can combine in pairs, especially at moderately low temperatures, to form the pale-yellow gas nitrogen tetroxide (N20.4). At normal terrestrial atmospheric pressure the latter condenses at ™ 9° C to a whitish solid. The suggestion was made that the polar caps are composed mainly of solid nitrogen tetroxide. The chief obstacle to the acceptance of this view is that the quantity of nitrogen dioxide in the atmosphere of Mars appears to be insignificant (p. 81).
Was this article helpful?