Uranus' stratospheric HCl upper limit from Herschel/SPIRE

TL;DR

This study used Herschel/SPIRE data to search for HCl in Uranus's stratosphere, setting upper limits on its abundance and providing insights into external sources and atmospheric composition.

Contribution

First to set upper limits on Uranus's stratospheric HCl using Herschel/SPIRE observations, constraining external source models.

Findings

HCl was not detected in Uranus's atmosphere.

Upper limits on HCl abundance were established.

Results are consistent with external sources and solar composition models.

Abstract

Herschel/SPIRE observations of Uranus are used to search for stratospheric hydrogen chloride (HCl) emission at 41.74 cm$^{-1}$. HCl was not detected and instead 3$\sigma$ upper limits were determined; $<$6.2 ppb ($<$2.0$\times$10$^{14}$ molecules/cm$^{2}$) for a 0.1 mbar step profile and $<$0.40 ppb ($<$1.2$\times$10$^{14}$ molecules/cm$^{2}$) for a 1 mbar step profile. HCl is expected to have an external source and these upper limits are consistent with abundances of other external species (CO, H$_2$O, CO$_2$) and a solar composition source.