We present spatially resolved (0 1-1 0) radio maps of Neptune taken from the Very Large Array and Atacama Large Millimeter/submillimeter Array between 2015 and 2017. Combined, these observations probe from just below the main methane cloud deck at ∼1 bar down to the NH4SH cloud at ∼50 bar. Prominent latitudinal variations in the brightness temperature are seen across the disk. Depending on wavelength, the south polar region is 5-40 K brighter than the mid-latitudes and northern equatorial region. We use radiative transfer modeling coupled to Markov Chain Monte Carlo methods to retrieve H2S, NH3, and CH4 abundance profiles across the disk, though only strong constraints can be made for H2S. Below all cloud formation, the data are well fit by -53.8+13.4 18.9 and -3.9+3.1 2.1 protosolar enrichment in the H2S and NH3 abundances, respectively, assuming a dry adiabat. Models in which the radio-cold mid-latitudes and northern equatorial region are supersaturated in H2S are statistically favored over models following strict thermochemical equilibrium. H2S is more abundant at the equatorial region than at the poles, indicative of strong, persistent global circulation. Our results imply that Neptune's sulfur-tonitrogen ratio exceeds unity, as H2S is more abundant than NH3 in every retrieval. The absence of NH3 above 50 bar can be explained either by partial dissolution of NH3 in an ionic ocean at GPa pressures or by a planet formation scenario in which hydrated clathrates preferentially delivered sulfur rather than nitrogen onto planetesimals, or a combination of these hypotheses.

We present Atacama Large Millimeter/submillimeter Array (ALMA) and Very Large Array (VLA) spatial maps of the Uranian atmosphere taken between 2015 and 2018 at wavelengths from 1.3 mm to 10 cm, probing pressures from ~1 to ~50 bar at spatial resolutions from 0 1 to 0 8. Radiative transfer modeling was performed to determine the physical origin of the brightness variations across Uranus's disk. The radio-dark equator and midlatitudes of the planet (south of ~50°N) are well fit by a deep H2S mixing ratio of 8.7+3.1- 1.5 ×10- 4 ( 37+13-6 × solar) and a deep NH3 mixing ratio of 1.7+0.7-0.4 ×10-4 ( 1.4+0.50.3× solar), in good agreement with models of Uranus's disk-averaged spectrum from the literature. The north polar region is very bright at all frequencies northward of ~50°N, which we attribute to strong depletions extending down to the NH4SH layer in both NH3 and H2S relative to the equatorial region; the model is consistent with an NH3 abundance of 4.7+2.1- 1.8 ×10-7 and an H2S abundance of <1.9×10-7 between ~20 and ~50 bar. Combining this observed depletion in condensible molecules with methane-sensitive near-infrared observations from the literature suggests large-scale downwelling in the north polar vortex region from ~0.1 to ~50 bar. The highest-resolution maps reveal zonal radio-dark and radio-bright bands at 20°S, 0°, and 20°N, as well as zonal banding within the north polar region. The difference in brightness is a factor of ~10 less pronounced in these bands than the difference between the north pole and equator, and additional observations are required to determine the temperature, composition, and vertical extent of these features.