Atmospheric Sulfur Photochemistry on Hot Jupiters

We develop a new one-dimensional photochemical kinetics code to address stratospheric chemistry and stratospheric heating in hot Jupiters. Here we address optically active S-containing species and CO 2 at 1200 ⩽ T ⩽ 2000 K. HS (mercapto) and S 2 are highly reactive species that are generated photochemically and thermochemically from H 2 S with peak abundances between 1 and 10 mbar. S 2 absorbs UV between 240 and 340 nm and is optically thick for metallicities [S/H]>0 at T ⩾ 1200 K. HS is probably more important than S 2 , as it is generally more abundant than S 2 under hot Jupiter conditions and it absorbs at somewhat redder wavelengths. We use molecular theory to compute an HS absorption spectrum from sparse available data and find that HS should absorb strongly between 300 and 460 nm, with absorption at the longer wavelengths being temperature sensitive. When the two absorbers are combined, radiative heating (per kg of gas) peaks at 100 μbars, with a total stratospheric heating of ∼8 × 10 4 W m −2 for a jovian planet orbiting a solar-twin at 0.032 AU. Total heating is insensitive to metallicity. The CO 2 mixing ratio is a well behaved quadratic function of metallicity, ranging from 1.6 × 10 −8 to 1.6 × 10 −4 for −0.3 < [M/H] < 1.7. CO 2 is insensitive to insolation, vertical mixing, temperature (1200 < T < 2000), and gravity. The photochemical calculations confirm that CO 2 should prove a useful probe of planetary metallicity.