The distribution of ammonia on Jupiter from a preliminary inversion of Juno Microwave Radiometer data

The Juno microwave radiometer measured the thermal emission from Jupiter's atmosphere from the cloud tops at about 1bar to as deep as a hundred bars of pressure during its first flyby over Jupiter (PJ1). The nadir brightness temperatures show that the Equatorial Zone is likely to be an ideal adiabat, which allows a determination of the deep ammonia abundance in the range 362-33+33ppm. The combination of Markov chain Monte Carlo method and Tikhonov regularization is studied to invert Jupiter's global ammonia distribution assuming a prescribed temperature profile. The result shows (1) that ammonia is depleted globally down to 50-60bars except within a few degrees of the equator, (2) the North Equatorial Belt is more depleted in ammonia than elsewhere, and (3) the ammonia concentration shows a slight inversion starting from about 7bars to 2bars. These results are robust regardless of the choice of water abundance. Plain Language Summary The distribution of ammonia gas on Jupiter's atmosphere was derived by fitting the microwave spectra measured by the Juno spacecraft. The result showed that the concentration of ammonia gas in the extratropics was much less than expected and had a local minimum near 7bars of pressure.