Meridional variations of C$_2$H$_2$ in Jupiter's stratosphere from Juno UVS observations

TL;DR

This study uses Juno UVS data to map the distribution of acetylene in Jupiter's stratosphere, revealing a decrease towards the poles consistent with insolation patterns and limited horizontal mixing.

Contribution

First to analyze meridional C₂H₂ distribution in Jupiter's stratosphere using Juno UVS observations, linking it to insolation and atmospheric mixing processes.

Findings

C₂H₂ abundance decreases by a factor of 2-4 towards the poles.

Distribution aligns with insolation-driven photochemistry.

Horizontal mixing rates are insufficient to homogenize latitudinal variations.

Abstract

The UVS instrument on the Juno mission records far-ultraviolet reflected sunlight from Jupiter. These spectra are sensitive to the abundances of chemical species in the upper atmosphere and to the distribution of the stratospheric haze layer. We combine observations from the first 30 perijoves of the mission in order to study the meridional distribution of acetylene (C$_2$H$_2$) in Jupiter's stratosphere. We find that the abundance of C$_2$H$_2$ decreases towards the poles by a factor of 2-4, in agreement with previous analyses of mid-infrared spectra. This result is expected from insolation rates: near the equator, the UV solar flux is higher, allowing more C$_2$H$_2$ to be generated from the UV photolysis of CH$_4$. The decrease in abundance towards the poles suggests that horizontal mixing rates are not rapid enough to homogenize the latitudinal distribution.