Evidence for auroral influence on Jupiter’s stratospheric composition revealed by ALMA

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. ALMA observations of HCN and CO in March 2017 show that CO was meridionally uniform and restricted to pressures lower than 3±1 mbar. HCN shared a similar vertical distribution in the low-to-mid latitudes, but was surprisingly depleted at pressures higher than 0.04(-0.03; +0.07) mbar in the polar regions. We propose that heterogeneous chemistry bonds HCN on large aurora-produced aerosols at these pressures in the jovian polar regions causing the observed depletion. We also propose that a relatively small fraction of CO causes enhanced production of CO2 inside the aurora to explain the long-term decrease of the CO column density and the CO2 peak observed only at southern polar latitudes in 2000.