Latitudinal variability in Jupiter's tropospheric disequilibrium species: GeH$_4$, AsH$_3$ and PH$_3$

TL;DR

This study uses high-resolution spectroscopy to investigate latitudinal variations in Jupiter's tropospheric gases, revealing differences between equatorial and polar regions despite challenges in disentangling cloud effects.

Contribution

The paper provides the first high-resolution spatially-resolved measurements of GeH$_4$, AsH$_3$, and PH$_3$ across Jupiter's latitudes, highlighting observed variability and contrasting with previous models.

Findings

AsH$_3$ and PH$_3$ are enhanced at high latitudes.

GeH$_4$ abundance remains roughly constant across latitudes.

Cloud and aerosol effects complicate abundance retrievals.

Abstract

Jupiter's tropospheric composition is studied using high resolution spatially-resolved 5-micron observation from the CRIRES instrument at the Very Large Telescope. The high resolving power (R=96,000) allows us to spectrally resolve the line shapes of individual molecular species in Jupiter's troposphere and, by aligning the slit north-south along Jupiter's central meridian, we are able to search for any latitudinal variability. Despite the high spectral resolution, we find that there are significant degeneracies between the cloud structure and aerosol scattering properties that complicate the retrievals of tropospheric gaseous abundances and limit conclusions on any belt-zone variability. However, we do find evidence for variability between the equatorial regions of the planet and the polar regions. Arsine (AsH$_3$) and phosphine (PH$_3$) both show an enhancement at high latitudes, while the abundance of germane (GeH$_4$) remains approximately constant. These observations contrast with the theoretical predictions from Wang et al. (2016) and we discuss the possible explanations for this difference.