Ammonia in Jupiter's troposphere from high-resolution 5-\textmu m spectroscopy

TL;DR

This study uses high-resolution 5-micron spectroscopy to analyze ammonia distribution in Jupiter's troposphere, revealing altitude-dependent abundance changes and localized ammonia enhancements near the North Equatorial Belt.

Contribution

It provides the first high-resolution spatially-resolved measurements of ammonia in Jupiter's troposphere, identifying altitude variations and a localized ammonia plume.

Findings

Ammonia abundance decreases with altitude in the 1-4 bar range.

Evidence of a localized ammonia enhancement at 4-6°N latitude.

Cloud opacity can mask large-scale latitudinal ammonia variability.

Abstract

Jupiter's tropospheric ammonia (NH\textsubscript{3}) abundance is studied using spatially-resolved 5-\textmu m observations from CRIRES, a high resolution spectrometer at the European Southern Observatory's Very Large Telescope. The high resolving power (R=96,000) allows the line shapes of three NH\textsubscript{3} absorption features to be resolved. We find that within the 1--4 bar pressure range, the NH\textsubscript{3} abundance decreases with altitude. The instrument slit was aligned north-south along Jupiter's central meridian, allowing us to search for latitudinal variability. There is considerable uncertainty in the large-scale latitudinal variability, as the increase in cloud opacity in zones compared to belts can mask absorption features. However, we do find evidence for a strong NH\textsubscript{3} enhancement at 4--6$^{\circ}$N, consistent with a localised `ammonia plume' on the southern edge of Jupiter's North Equatorial Belt.