Program: GN-2020A-Q-113

We propose to measure the ongoing evolution of vertical aerosol structure in several key features of Jupiter’s atmosphere, concomitantly with Juno spacecraft measurements. Our goal is to determine or constrain the physical and chemical processes controlling the relevant phenomena, each of which extends and enhances contemporaneous observations by the Juno mission or future observations by providing a context in time. (1) A quasi-periodic Equatorial Zone (EZ) disturbance causes a brownish coloration of a normally white appearance and creates large swaths of anomalously cloudless and desiccated areas in a region of Jupiter that is normally cloudy and moist. Such a state is at odds with Juno’s Microwave Radiometer (MWR) observations that imply that the EZ has uniformly deep-rooted upwelling motions causing cloudy wet conditions at all longitudes. We appear to be at the beginning of such a disturbance, which should be in a mature stage in semester 2020A, based on historical records. We propose obtaining high-resolution NIRI images contemporaneously with the MWR observations of the EZ at Juno’s 26th close approach (“perijove”) when the spacecraft orientation will be changed to enable MWR access to near-equatorial latitudes specifically to determine the deep atmospheric structure associated with this EZ disturbance. These observations will also provide a vertical and horizontal context for the more limited observations of Juno’s visible camera (JunoCam) and 2-5 µm camera/spectrometer (JIRAM). (2) Major perturbations to the typical appearance of Jupiter’s Great Red Spot (GRS) that took place in 2019 May are expected to be repeated, as a result of the ever-decreasing longitudinal extent of the GRS and its frequent interactions with smaller vortices. The 3-dimensional structure of these interactions and the responsible dynamics are not well understood, and the high-resolution NIRI observations will provide critical constraints on models for such interactions. They will also document the pace of changes to 3-dimensional structure of the GRS as a function of its continued longitudinal shrinking. We will also measure changes to the 3-dimensional structure of Oval BA (“the little red spot”) to determine changes following its very recent return to a pre-2005 uniformly white appearance. (3) The evolution of aerosol properties of Jupiter’s polar regions and their distribution is also of considerable interest to the Juno mission. Such observations will provide contextual information for the MWR, which will continue to sample the north polar region with increasing spatial resolution, as well as the JunoCam and JIRAM instruments which will continue to sample portions of the south polar region. The proposed observations will provide a critical component of a campaign of Earth-based support for Juno (https://www.missionjuno.swri.edu/planned-observations) that is not available at any other facility.