Probing the Jupiter-Io interaction with synergistic measurements of radio and ultraviolet auroral emissions from Juno, Nançay and HST observatories

<p>The prominent component of Jovian decametric (auroral) emissions is induced by Io. Io decametric emissions (Io-DAM) have thus been monitored on a regular basis by Earth- or Space-based radio observatories for several decades. They display a typical arc-shaped structure in the time-frequency plane which results from the motion of the Io flux tube relative to the observer convolved with the anisotropic radio emission cone. Remote determination of the Io-DAM beaming pattern was used to check the emission conditions at the source (e.g. Queinnec & Zarka, 1998). It has been done at several occasions using various models of magnetic field/lead angles which introduce significant uncertainties. Nevertheless, Io-DAM arcs were shown to be consistent with oblique emissions triggered by the Cyclotron maser Instability from loss-cone electron distributions of a few keVs (Hess et al., 2008). The CMI validity for Jovian DAM and the prominence of loss cone electron distributions has been later confirmed by Juno in situ measurements (e.g. Louarn et al, 2017). In this study, we took advantage of simultaneous radio/UV or bi-point stereoscopic radio measurements provided by Juno/Waves, the Nançay Decameter Array and the Hubble Space Telescope to unambiguously derive the beaming pattern of several Io-DAM arcs and compare it with theoretical expectations. We then assess the energy of CMI-unstable auroral electrons at the source and discuss our results at the light of similar independent studies reaching different conclusions.</p>

Atmospheres on Callisto composed of sublimated water vapor and its photochemical products

<p class="western" align="justify">The parameter space for the very uncertain composition of sublimated H2O and its photochemical products H and H2 in Callisto's atmosphere is examined using the Direct Simulaton Monte Carlo (DSMC) method.</p> <p class="western" align="justify">We focus on two significantly different versions of H2O production in which:</p> <p class="western" align="justify">(1) the ice and dark, non-ice/ice-poor material are intimately mixed and H2O sublimates at Callisto's warm day-side temperatures (e.g., as in most atmospheric modeling efforts at Callisto to date [1-4]); and</p> <p class="western" align="justify">(2) the ice and dark, non-ice/ice-poor material are segregated (e.g., consistent with interpretations of images of Callisto's surface taken by Voyager [5, 6] and Galileo [7]) and H2O sublimates at "ice" temperatures [8].</p> <p class="western" align="justify">Our 2D molecular kinetic models track the motion H2O, whose sublimation yield varies several orders of magnitude depending on the description of Callisto's surface, its photochemical products H and H2, and a relatively dense O2 component. Whereas H is assumed to react in the regolith on return to the surface, H2 is assumed to thermalize and re-enter the atmosphere.</p> <p class="western" align="justify">We compare the simulated LOS column densities of H to the detected H corona at Callisto [9], which was suggested to be produced primarily by photodissociation of sublimated H2O. Our goal is to use the corona observations to help constrain the source rate for H2O from Callisto’s complex surface.</p> <p class="western" align="justify"><strong>References</strong></p> <p class="western" align="justify">[1] Liang et al., 2005. Atmosphere of Callisto. <em>Journal of Geophysical Research: Planets</em>.</p> <p class="western" align="justify">[2] Vorburger et al., 2015. Monte-Carlo simulation of Callisto’s exosphere. <em>Icarus</em>.</p> <p class="western" align="justify">[3] Hartkorn et al., 2017. Structure and density of Callisto’s atmosphere from a fluid-kinetic model of its ionosphere: Comparison with Hubble Space Telescope and Galileo observations. <em>Icarus.</em></p> <p class="western" align="justify">[4] Carberry Mogan et al., 2021 (<em>under review</em>). A tenuous, collisional atmosphere on Callisto. <em>Icarus</em>.</p> <p class="western" align="justify">[5] Spencer and Maloney, 1984. Mobility of water ice on Callisto: Evidence and implications. <em>Geophysical Research Letters</em>.</p> <p class="western" align="justify">[6] Spencer, 1987. Thermal segregation of water ice on the Galilean satellites. <em>Icarus</em>.</p> <p class="western" align="justify">[7] Moore et al., 1999. Mass movement and landform degradation on the icy Galilean satellites: Results of the Galileo nominal mission. <em>Icarus</em>.</p> <p class="western" align="justify">[8] Grundy et al., 1999. Near-infrared spectra of icy outer solar system surfaces: Remote determination of H2O ice temperatures. <em>Icarus</em>.</p> <p class="western" align="justify">[9] Roth et al., 2017. Detection of a hydrogen corona at Callisto. <em>Journal of Geophysical Research: Planets</em>.</p>

The SuperCam Instrument Suite on the Mars 2020 Rover: Science Objectives and Mast-Unit Description

On the NASA 2020 rover mission to Jezero crater, the remote determination of the texture, mineralogy and chemistry of rocks is essential to quickly and thoroughly characterize an area and to optimize the selection of samples for return to Earth. As part of the Perseverance payload, SuperCam is a suite of five techniques that provide critical and complementary observations via Laser-Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman and Luminescence (TRR/L), visible and near-infrared spectroscopy (VISIR), high-resolution color imaging (RMI), and acoustic recording (MIC). SuperCam operates at remote distances, primarily 2–7 m, while providing data at sub-mm to mm scales. We report on SuperCam’s science objectives in the context of the Mars 2020 mission goals and ways the different techniques can address these questions. The instrument is made up of three separate subsystems: the Mast Unit is designed and built in France; the Body Unit is provided by the United States; the calibration target holder is contributed by Spain, and the targets themselves by the entire science team. This publication focuses on the design, development, and tests of the Mast Unit; companion papers describe the other units. The goal of this work is to provide an understanding of the technical choices made, the constraints that were imposed, and ultimately the validated performance of the flight model as it leaves Earth, and it will serve as the foundation for Mars operations and future processing of the data.