Oxygen is the most common element after hydrogen and helium in Jupiter's atmosphere, and may have been the primary condensable (as water ice) in the protoplanetary disk. Prior to the Juno mission, in situ measurements of Jupiter's water abundance were obtained from the Galileo Probe, which dropped into a meteorologically anomalous site. The findings of the Galileo Probe were inconclusive because the concentration of water was still increasing when the probe died. Here, we initially report on the water abundance in the equatorial region, from 0 to 4 degrees north latitude, based on 1.25 to 22 GHz data from Juno Microwave radiometer probing approximately 0.7 to 30 bars pressure. Because Juno discovered the deep atmosphere to be surprisingly variable as a function of latitude, it remains to confirm whether the equatorial abundance represents Jupiter's global water abundance. The water abundance at the equatorial region is inferred to be. !. %. × ppm, or. !. %. times the protosolar oxygen elemental ratio to H (1 uncertainties). If reflective of the global water abundance, the result suggests that the planetesimals formed Jupiter are unlikely to be water-rich clathrate hydrates. From thermodynamic calculations 1 , three types of cloud layers in the Jovian atmosphere are thought to exist: an ammonia ice cloud, an ammonium hydrosulfide ice cloud 2,3 , and a water ice and droplet cloud, formed approximately at 0.7 bars, 2.2 bars, and 5 bars, respectively, assuming solar abundances. The locations of these clouds may vary due to the local abundance, meteorology and specific model parameters. Condensation and evaporation of water contribute to weather on giant planets because water is the most abundant species apart from hydrogen and helium and the latent heat flux in convective storms is comparable to the solar and internal heat fluxes 4,5. Consequently, the thermal state of the atmosphere is affected by the amount of water vapor in the atmosphere. Prior to the Juno mission, in situ measurements of Jupiter's atmospheric composition below the clouds were obtained from the Galileo Probe 6 , which dropped into a meteorologically anomalous site (6.57° N planetocentric latitude , 4.46° W longitude) 7 , known as a 5 "hot spot" near the boundary between the visibly-bright Equatorial Zone (EZ) and the dark North Equatorial Belt (NEB) 8. The findings of the Galileo Probe were baffling, for they showed that the levels where ammonia and hydrogen sulfide become uniformly

The Galilean moons of Jupiter are known to have atmospheres and ionospheres, detected with both ground-based observations and spacecraft data. An oxygen-hydrogen atmosphere was discovered on Ganymede with observations by the Hubble Space Telescope (Hall et al., 1998). Ganymede is a unique object in the solar system in that it has its own intrinsic magnetic field which interacts with the Jovian magnetosphere (Kivelson et al., 1997). Within the open field line regions at higher latitudes, sputtering generates an atmosphere of molecular oxygen subject to ionization and dissociated excitation from the Jovian magnetosphere (Eviatar et al., 2001). Within closed field line regions, it is expected the atmosphere is produced by sublimation (Eviatar et al., 2001). It is thought the ionosphere is generated from the neutral atmosphere via photoionization and electron impact from the Jovian magnetosphere (Carnielli et al., 2019). Prior to Juno's encounter with Ganymede, the only direct measurements of Ganymede's ionosphere were those acquired in-situ measurements from the Galileo particle detectors and by the Galileo radio occultation experiment. Due to the flyby distance of the in-situ spacecraft measurements, radio occultation data provide valuable information about the electron densities near the surface of Ganymede.The Galileo spacecraft executed a total of eight S-band radio occultations of Ganymede throughout its mission, resulting in five non-detections, two weak detections, and one strong detection of an ionosphere (McGrath et al., 2004). To the best of our knowledge, the Galileo radio science data at Ganymede were never archived. In particular with respect to Ganymede, only occultation profiles from the G8 encounter were ever published in scientific literature. The strong ionosphere detection occurred during the Ganymede G8 egress occultation resulting in a peak electron density of ∼5,000 cm −3 near the surface (Kliore, 1998). Initially, the lack of detection was surprising, but it was hypothesized that positive detections occurred where the trailing hemisphere (where the

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Described here is a concept for a variable-altitude aerobot mission to Venus developed as part of the 2020 NASA Planetary Science Summer School in collaboration with NASA Jet Propulsion Laboratory. The Venus Air and Land Expedition: a Novel Trailblazer for in situ Exploration (VALENTInE) is a long-duration New Frontiers–class mission to Venus in alignment with the goals recommended by the 2013 Planetary Science Decadal Survey. VALENTInE would have five science objectives: (1) determine the driving force of atmospheric superrotation, (2) determine the source of D/H and noble gas inventory, (3) determine the properties that govern how light is reflected within the lower cloud later, (4) determine whether the tesserae are felsic, and (5) determine whether there is evidence of a recent dynamo preserved in the rock record. The proposed mission concept has a total duration of 15 Earth days and would float at an altitude of 55 km, along with five dips to a lower altitude of 45 km to study Venus’s lower atmosphere. The instrument payload allows for measurements of the atmosphere, surface, and interior of Venus and includes six instruments: an atmospheric weather suite, a mass spectrometer, a multispectral imager, a near-infrared spectrometer, light detection and ranging, and a magnetometer. Principle challenges included a limitation caused by battery lifetime and low technology readiness levels for aerobots that can survive the harsh conditions of Venus’s atmosphere. This preliminary mission was designed to fit within an assumed New Frontiers 5 (based on inflated New Frontiers 4) cost cap.

Jupiter's aurorae reflect microwave radiation emitted upward from Jupiter's atmosphere and downward from the cold sky above due to regions in the auroral plasma with increased electron densities. The lack of thermal radiation from the atmosphere was observed by Juno's Microwave Radiometer (MWR) on overflights of the aurorae during seven different orbits. Out of Juno's first 21 orbits, seven orbits inferred enhanced electron densities in Jupiter's auroral arcs. The most profound disruption in microwave emission was observed during Perijove 5. This perijove demonstrated the most significant cold spot for Channel 1 (0.6 GHz), with cold spots also present in Channels 2 (1.25 GHz) and 3 (2.6 GHz) in a location where the influence of Jupiter's moon, Io, likely increased the electron density in Jupiter's aurora. The maximum electron densities retrieved from Channel 1 are on the order of 3 × 109 cm−3, and in the presence of the Io flux tube, electron densities could reach 1010 cm−3 affecting Channels 2 and 3.