A study of the upper atmosphere of Uranus using the IUE

IUE data on the 1600-2000 A spectral features for Uranus during 1980 are discussed in comparison with equivalent data for Saturn and Jupiter. Attention was focused on detecting possible temporal changes in the C2H2 abundance at 1700 A. The C2H2 abundance in 1980 is estimated to have been a column density of 3.4-10.2 x 10 to the 16th/sq cm. The presence of C2H2 was attributed to photochemical reactions in a layer below 100 km altitude, and was not controlled by saturation, which took place at lower altitudes. A K value of 100,000-1 million/sq cm per sec for Uranus was comparable to Jupiter's and 10-100 times lower than Saturn's.