Comparative Analysis of the Behavior of Weak Absorption Bands of Ammonia at 552 and 645 Nm in the Spectrum of Jupiter

Abstract

This article contains the first obtained results of measuring the latitudinal variations of the very weak ammonia (NH3) absorption band at 552 nm along the central Jupiter meridian based on spectral observations in 2019. This study is preliminary in nature as the first attempt to clarify the possibility and advisability of further detailed study of this weak ammonia band behavior on the Jupiter disk. We obtained the latitude variations of the equivalent widths and equivalent absorption paths for the 552 nm NH3 band and, for comparison, the same characteristics for the more intense, but also weak NH3 645 nm band. The absorption maximum in both bands is observed in the equatorial zone, where in the center of the disk their equivalent widths are: W (552 nm) = 2.58 ± 0.29 A and W (645 nm) = 6.77 ± 0.25 A. A feature that distinguishes the behavior of the 552 nm NH3 band from the 645 nm NH3 band is a steeper decrease in absorption towards high latitudes, as well as small differences in the positions of absorption extrema in latitudes. The effect of latitudinal differences in the position of the extrema of the methane absorption bands was discovered by us as early as 1999 observations and was later noted also in the ammonia absorption bands. These features reflect structural differences in the Jupiter cloud layer and its troposphere and can serve as one of the means for its (troposphere) optical sounding.