Evidence for auroral influence on Jupiter's nitrogen and oxygen chemistry revealed by ALMA

TL;DR

This study uses ALMA observations to reveal how auroral processes influence the distribution and chemistry of nitrogen and oxygen species, particularly HCN, in Jupiter's stratosphere, highlighting aurora-driven heterogeneous chemistry.

Contribution

It provides the first high-resolution joint observations of CO and HCN distributions at Jupiter's poles, demonstrating auroral influence on nitrogen chemistry through aerosol interactions.

Findings

CO is uniformly distributed at pressures below 3 mbar.

HCN is depleted in auroral regions at specific pressure levels.

Auroral aerosols likely cause HCN depletion via heterogeneous chemistry.

Abstract

The localized delivery of new long-lived species to Jupiter's stratosphere by comet Shoemaker-Levy 9 in 1994 opened a window to constrain Jovian chemistry and dynamics by monitoring the evolution of their vertical and horizontal distributions. However, the spatial distributions of CO and HCN, two of these long-lived species, had never been jointly observed at high latitudinal resolution. Atacama large millimeter/submillimeter array observations of HCN and CO in March 2017 show that CO was meridionally uniform and restricted to pressures lower than 3 $\pm$ 1 mbar. HCN shared a similar vertical distribution in the low- to mid-latitudes, but was depleted at pressures between 2$^{+2}_ {-1}$ and 0.04$^{+0.07}_{-0.03}$ mbar in the aurora and surrounding regions, resulting in a drop by two orders of magnitude in column density. We propose that heterogeneous chemistry bonds HCN on large aurora-produced aerosols at these pressures in the Jovian auroral regions causing the observed depletion.