The Jovian atmospheric window at 2.7 μm: A search for H2S

Abstract

The atmospheric transmission window at 2.7 μm in Jupiter's atmosphere was observed at a spectral resolution of 0.1 cm−1 from the Kuiper Airborne Observatory. From analysis of the CH4 abundance (∼80m-am) and the H2O abundance (<0.0125cm-am) it was determined that the penetration depth of solar flux at 2.7 μm is near the base of the NH3 cloud layer. The upper limit to H2O at 2.7 μm and other recent results suggest that photolytic reactions in Jupiter's lower troposphere may not be as significant as was previously thought. The search for H2S in Jupiter's atmosphere yielded an upper limit of ∼0.1cm-am. The corresponding limit to the elemental abundance ratio [S]/[H] was ∼1.7 × 10−8, about 10−3 times the solar value. Upon modeling the abundance and distribution of H2S in Jupiter's atmosphere it was concluded that, contrary to expectations, sulfur-bearing chromophores are not present in significant amounts in Jupiter's visible clouds. Rather, it appears that most of Jupiter's sulfur is locked up as NH4SH in a lower cloud layer. Alternatively, the global abundance of sulfur in Jupiter may be significantly depleted.