ON THE LATITUDE VARIATION OF AMMONIA, ACETYLENE, AND PHOSPHINE ALTITUDE PROFILES ON JUPITER FROM HST FAINT OBJECT SPECTROGRAPH OBSERVATIONS

Ultraviolet spectra in the spectral region from 160 to 230 nm were tak en with the Hubble Space Telescope Faint Object Spectrograph in May 19 92. We analyze these data to obtain the altitude distribution of ammon ia and its variation with latitude from 6 degrees N to 25 degrees N. A mmonia condenses below the 150-mbar level, above which it departs from saturation due to photolysis. Using a photochemical model, we also de rive the value of atmospheric eddy mixing coefficients at the observed latitudes. It is found that the eddy diffusion coefficient varies fro m 1.5 x 10(4) cm(2) s(-1) at 450 mbar to 4.9 x 10(2) cm(2) s(-1) at 12 0 mbar. The vertical distribution of ammonia and the eddy diffusion co efficient do not show a large variation with latitude. We also determi ne an acetylene mixing ratio of (10-30) x 10(-9) near 80 mbar and an u pper limit of 1.5 x 10(-7) for the phosphine mixing ratio, if PH3 is m ixed uniformly below the 140 mbar level. The existence of particulate haze at low and high latitudes Is also investigated. (C) 1998 Academic Press.