Ammonia Abundance Derived from Juno MWR and VLA Observations of Jupiter

Abstract

The vertical distribution of trace gases in planetary atmospheres can be obtained with observations of the atmosphere’s thermal emission. Inverting radio observations to recover the atmospheric structure, however, is nontrivial, and the solutions are degenerate. We propose a modeling framework to prescribe a vertical distribution of trace gases that combines a thermochemical equilibrium model with a vertical temperature structure and compare these results to models where ammonia can vary between predefined pressure nodes. We compare these model to nadir brightness temperatures and limb-darkening parameters, together with their uncertainties, which we reduced from the raw Juno Microwave Radiometer (MWR) data set. We then apply this framework to MWR observations during Juno’s first years of operation (perijove passes 1–12) and to longitudinally averaged latitude scans taken with the upgraded Very Large Array. We use the model to constrain the distribution of ammonia between −60° and 60° latitude and down to 100 bars. We constrain the ammonia abundance to be 340.5 − 21.2 + 34.8 ppm ( 2.66 − 0.17 + 0.27 × solar abundance) and find a depletion of ammonia down to a depth of ∼20 bars, which supports the existence of processes that deplete the atmosphere below the ammonia and water cloud layers. At the equator we find an increase of ammonia with altitude, while the zones and belts in the midlatitudes can be traced down to levels where the atmosphere is well mixed. The latitudinal variation in the ammonia abundance appears to be opposite to that shown at higher altitudes, which supports the existence of a stacked-cell circulation model.

Latitudinal Variations in Methane Abundance, Aerosol Opacity and Aerosol Scattering Efficiency in Neptune's Atmosphere Determined From VLT/MUSE

“…This simple “stacked circulation” view (e.g., Fletcher et al., 2020; Tollefson et al., 2019), however, is inconsistent with the banded structure seen here at methane continuum wavelengths longer than 650 nm and may also be inconsistent with retrieved H 2 S abundances (at 1.5 μm) at pressures less than 5 bar (Irwin et al., 2019b), suggesting that the circulation may actually be even more complicated than previously thought. An interesting analogy is the distribution of NH 3 seen in Jupiter's deep atmosphere by the Juno spacecraft (Li et al., 2017), which appears to rise in an equatorial plume, with much greater abundances than at mid‐latitudes, although a more zonal NH 3 structure is seen at the 0.5–2‐bar level by both Juno (Fletcher et al., 2021), and also in mid‐infrared observations (e.g., Fletcher et al., 2016); this is believed to arise and be maintained by a similar double “stacked cell” system (e.g., de Pater et al., 2023; Duer et al., 2021; Fletcher et al., 2021; Ingersoll et al., 2000; Moeckel et al., 2023; Showman & de Pater, 2005).…”

Stable three-dimensional vortex families consistent with Jovian observations including the Great Red Spot

“…(2019) and Moeckel et al. (2023), along with (2.12) and (2.13) to obtain first guesses of , and as shown by the blue dots in figure 2. Although the temperature data appear to be smooth, when we differentiate to compute with (2.25 a , b ), we find that it is not smooth, especially at heights deeper than mbar (see the blue dots in figure 2 d ).…”

“…Our calculations are carried out using the observed atmospheric temperature and pressure (de Pater et al. 2019; Moeckel, de Pater & DeBoer 2023), which consists of a highly stratified region at heights above a convection zone (see § 3 for details). The atmosphere is highly stratified at the top of our computational domain and has , where is the Brunt–Väisälä frequency of the atmosphere, and is the local Coriolis frequency.…”

Noble Gas Planetology and the Xenon Clouds of Uranus

“…The data are plotted as ratios to solar abundances (Lodders 2019). For the Jovian N/H 2 ratio, we use an NH 3 abundance of -+ 340 17 27 ppmv (Moeckel et al 2023), to which we add the putative NH 4 SH cloud using H 2 S, as reported by the Galileo Probe (Wong et al 2004). The open blue triangle is a Juno inference of equatorial H 2 O (Li et al 2020).…”