Candice Hansen

Araneiforms are enigmatic dendritic negative topography features native to Mars. Found across a variety of substrates and exhibiting a range of scales, morphologies, and activity level, they are hypothesized to form via insolation‐induced basal sublimation of seasonal CO2 ice. With no direct Earth analog, araneiforms are an example of how our understanding of extant surface features can evolve through a multipronged approach using high resolution change‐detection imaging, conceptual and numerical modeling, and analog laboratory work. This review offers a primer on the current state of knowledge of Martian araneiforms. We outline the development of their driving conceptual hypothesis and the various methodologies used to study their formation. We furthermore present open questions and identify future laboratory and modeling work and mission objectives that may address these questions. Finally, this review highlights how the study of araneiforms may be used as a proxy for local conditions and perhaps even past seasonal dynamics on Mars. We also reflect on the lessons learnt from studying them and opportunities for comparative planetology that can be harnessed in understanding unusual features on icy worlds that have no Earth analog.

For the first time, model-derived and imagery-derived wind directions and speeds have been compared in Mars’s south polar region. Seasonal fan-shaped deposits are routinely observed by HiRISE in the polar regions. They are widely accepted to result from CO2 gas jet eruptions. Fan lengths, sizes, and shapes can provide information about wind directions and strengths at the times such eruptions occur. We utilize a catalog of those fan-shaped deposits, marked by citizen scientists within the framework of the Planet Four (P4) project, at 27 regions of interest (ROIs) for two spring seasons (Mars years 29 and 30). Fans change considerably from one HiRISE image to another at most of these ROIs as wind direction changes over the spring season. Leveraging this characteristic, intraseasonal variations in near-surface wind speeds and directions were retrieved and compared to near-surface winds predicted by a mesoscale atmospheric model (MRAMS) at the same ROIs. At most ROIs P4-inferred wind directions are consistent with those from MRAMS. The P4-derived wind speeds are less constrained but are consistent with MRAMS wind speeds at the majority of ROIs. The overall consistency between the P4-inferred and MRAMS wind directions supports the underlying assumption that fan formation is controlled by the wind and is not simply due to ballistic trajectories of material exiting suitably nonvertical vents. Measurements of seasonal fan-shaped deposits in HiRISE imagery can thus provide important intraseasonal information about near-surface winds—invaluable for both validating climate modeling and quantitatively investigating Mars’s polar processes.

JunoCam, Juno's wide-angle visible light camera, has been able to take series of close-up RGB images of the same Jupiter cloud-tops from different angles within only several minutes.Within this kind of long-baseline observations, cloud motion usually takes a less prominent role than parallax.  We select features in which it appears reasonable to assume that all relative cloud displacements can be attributed to parallax.  Although we do not assume that we can determine absolute camera pointing with sufficient accuracy, we can determine relative camera pointing very well, at least locally.  We first reproject two suitable JunoCam images to the same perspective. Then we stereo-correspond a pair of nearby patches of the first selected image with that of the second image. The change of the distances between the two patches returns our desired parallax.Such stereo-corresponding patches can only be determined in a sufficiently reliable way, if both patches have sufficient small-scale c...

<p>On November 29<sup>th</sup>, 2021, the Juno Spacecraft completed its 38<sup>th</sup> perijove as part of its Extended Mission. Three of the spacecraft’s instruments, JunoCam, JIRAM, and MWR, imaged a thunderstorm in the North Equatorial Belt (NEB) at approximately 9<sup>o</sup>N planetocentric latitude.  JunoCam and the MWR captured data from an altitude of a few thousand kilometers, following JIRAM’s images of the storm four hours before. Ground-based observers tracked this storm over a period of a few days, providing a planetary-scale perspective to Juno’s observations.  This region of the planet has been quite active throughout 2021 and 2022. </p><p> </p><p>The morphology of the storm as shown in JunoCam’s RGB filters (observations with the methane filter were not conducted), and from ground-based observers, is highly suggestive of a moist-convective thunderstorm complex with clouds reaching the upper troposphere. Furthermore, JunoCam images suggest that the storm is shaped by vertical shear as the presumed anvil is offset from a thicker region of white clouds. On Earth, vertical shear is necessary for non-tropical cyclone thunderstorm systems to persist for prolonged periods.  JunoCam imaging also suggests a previous anvil top located to the west of the optically thick clouds, which may indicate a temporarily-varying nature to the convection, which is consistent with ground-based observations showing upwelling at this location for several days before the Juno images. JIRAM’s observations show a cold spot at 4.78 µm near the region of the thickest white clouds, which would be expected from optically thick clouds blocking heat transport to space. Spectroscopic retrievals show a slight enhancement of H<sub>2</sub>0 and PH<sub>3</sub> compared to the surrounding region, which is expected from upwelling from the interior. The microwave radiometer (MWR) instrument detected numerous lightning flashes at 0.6 GHz (Channel 1) and several flashes at 1.2 and 2.4 GHz (Channels 2 and 3, respectively), which are correlated with JunoCam and JIRAM’s observations of optically thick clouds.  However, the brightness temperature signals of the storm in the MWR observations appears to be confined to the upper most 9 bars of the atmosphere ("weather layer") indicating that a deep-seated convective plume originating from beneath the water-cloud base is probably not responsible for this storm system.  Instead, a humidity or temperature front contained within the weather layer may be a likely source.</p><p> </p><p>These observations may ultimately shed light on the mechanisms that form, sustain, and characterize moist convective storms in hydrogen-dominated atmospheres.  Here we summarize our observations to date and compare the PJ38 storm to other storms in Jupiter's NEB and those on Saturn. </p>

Jupiter is known for its active meteorology and stormy weather, but still remaining are the questions how high are its clouds and what are they made of? Using images acquired by JunoCam, Juno’s visible light camera, we analyze the length of the clouds’ shadows to infer their heights. We focus on the “Nautilus” a 3000-km cyclonic vortex seen during Juno’s 14th perijove and observed simultaneously with the Hubble Space Telescope. We show that individual clouds or cloud fronts with typical lengths of ∼200 km extend about ∼10 to 20 km above the deeper surrounding cloud deck. That white cloud deck forms the spiral of the cyclone, which we show lies ∼20 to 30 km above a reddish-colored region. An analysis of the HST images confirms that the white region is higher than its surrounding darker, reddish cloud deck. These respective elevations are consistent with the white clouds being made of fresh ammonia ice while most of the reddish clouds underneath are made of ammonium hydrosulfide NH4SH...

Exploration of the local ice giant Neptune has been stymied by a perception that an orbiter (i.e., a Galileoor Cassini-like flagship mission) is required for major scientific progress. We assert that advances in our understanding of these systems (atmospheres, rings, and moons)—as well as our understanding of the populace of the Kuiper Belt—have changed dramatically since Voyager (Fig. 1), thus a simple spacecraft equipped with modern technology will yield significant new icegiant system science. We describe a mission that flies by the Neptune system and continues on to explore a Kuiper Belt object (KBO). Figure 1: Neptune then and now. Nearly all aspects of the Neptune system have evolved considerably in the decades since the Voyager flyby, as have the technologies available to flight missions. Although the Voyager image is at visible wavelengths and the Keck image is in the near IR, visible HST images reveal the changes are intrinsic, not due to wavelength [1,2]. Scientific Motiva...

The seasonal sublimation of CO2 ice is an active driver of present-day surface change on Mars. Diniega et al (2013) proposed that a discrete type of Martian gully, found on southern hemisphere dunes, were formed by the movement of CO2 seasonal ice blocks. These ‘Linear Gullies’ consist primarily of long (100 m 2.5 km) grooves with near-uniform width (few-10 m wide), and typical depth of <2 m. They are near-linear throughout most of their length but sometimes contains zones of low-to-high sinuosity. They are commonly bounded by levées. The groove is generally prefaced by a small alcove that originates at the dune brink.

<p>The Juno spacecraft’s polar orbit with periapses (perijove; PJ) within a few thousand kilometers of the 1-bar level has allowed for detailed observations of Jupiter’s thunderstorms from multiple instruments at unprecedented resolution.  Here, we detail the observations of a 2,500-km wide thunderstorm feature located in the North Equatorial Belt (at planetocentric latitude 9°N; Fig. 1) from the six channels of the Microwave Radiometer Instrument (MWR), from JunoCam’s RGB filters, from the Jovian Infrared Auroral Mapper’s (JIRAM) 5-micron band, and from supporting Earth-Based images taken during near the time of the 38<sup>th</sup> perijove. Juno flew over one such thunderstorm complex at close range (~5,000 km) on 29 Nov. 2021 for the first time with a favorable alignment to observe such a feature at low emission angles. JunoCam and MWR observations were taken nearly simultaneously while JIRAM’s data was collected approximately 4.5 hours prior. </p> <p>Moist convection is widely thought to play a large role in transporting heat from Jupiter’s interior through the weather layer (here defined as 10 to 0.7 bar) and then to space. In the process, heat transport allows for moist convection, which powers thunderstorms and generates small-scale turbulence that, through the inverse-cascade mechanism, generates large-scale vortices and zonal jets.  Convective instability allows for strong updrafts that carry volatiles such as NH<sub>3</sub> and H<sub>2</sub>O from the base of the water-cloud (and deeper) upwards to form cumulonimbus (CB) clouds.  The tops of these CB towers diverge outwards and are shaped by local winds to form an icy anvil cloud much as they do on Earth.</p> <p> </p> <p>Lightning is a defining characteristic of CB clouds and the MWR instrument detected numerous flashes in and around the bright white feature with a storm-like morphology clearly observed by JunoCam. JIRAM’s M-band filter images clearly show the structure of the cloud tops, matching observations from JunoCam once the zonally-averaged motion over the 4.5-hour time separation is accounted for. Figure 2 is a JIRAM image with a noticeable dark ‘notch,’ which is where the optically thick storm clouds are located. Preliminary spectral analysis from JIRAM shows a slightly enhanced signal of H<sub>2</sub>O and PH<sub>3</sub> near the anvil top but NH<sub>3</sub> ice is undetectable in these night-time JIRAM observations.</p> <p> </p> <p>Gaseous NH<sub>3</sub> and H<sub>2</sub>O are partially opaque to wavelengths sensed by the MWR instrument.  Each of the six channels of MWR have a sensitivity that peaks at different altitudes in the atmosphere, which allows us to sound the brightness temperature and the vertical structure from the cloud tops down to many tens of bars.  The brightness temperature is a combination of air temperature and humidity, and, at present, we are unable to deconvolve these two measurements. Nevertheless, sounding the brightness temperature provides information on the depth and structure of a tall atmospheric feature and we present brightness temperature maps for all six channels.</p> <p>We observe that this particular thunderstorm complex is visible from the cloud tops (~0.7 bar) down to approximately the level of the water cloud. Below this level, the thunderstorm signal is no longer apparent, which indicates that any dry convective updraft carrying MWR opacity-inducing vapor is either not present, or its air temperature and humidity are combined in such a way to mask its presence perfectly. If this thunderstorm is a result of dry convection from below the base of the water cloud lifting moist air to the level of free convection (LFC) then the effect of the dry convection is to lift vapor already located around the base of the water-cloud level rather than bringing up significantly moist air from deep below the base of the water cloud, or otherwise a signal would be detected in the short wavelength channels of MWR (See Fig. 3 for a cloud-top MWR map).</p> <p>The next several perijoves will feature an orientation for the MWR instrument that is conducive for low emission angle observations. Additionally, the latitude of perijove is slowly migrating northward and, if Juno does fly over new thunderstorms, we may have the opportunity to compare the vertical structure of multiple thunderstorms taken from different regions of the planet at high resolution from multiple instruments.</p> <p><img src="" alt="" /></p> <p>Figure 1: PJ38 Thunderstorm from JunoCam Image JNCE_2021333_38C00030_V01 (left) and close-up  (right: Image Credit:…

<p><strong>Introduction</strong></p> <p>The extended portion of NASA’s Juno mission began on 1 August 2021 and will continue through September 2025. The extended mission expands Juno’s science goals beyond those of the prime mission, as noted at the last EPSC (Orton et al.  EPSC2021-58).  Atmospheric studies will continue to be among the foremost of science goals and an area in which the world-wide community of Jupiter observers can provide significant contextual support.  Juno’s remote-sensing observations will take advantage of the migration of its closest approaches (“perijoves” or PJs) toward increasingly northern latitudes.  The observations should include close-ups of the circumpolar cyclones and semi-chaotic cyclones known as “folded filamentary regions”. A series of radio occultations will provide vertical profiles of electron density and the neutral-atmospheric temperature over several atmospheric regions. The mission will also map the variability of lightning on Jupiter’s night side.</p> <p><strong>Physical Details of the Mission</strong></p> <p>The sequence of orbits and key investigations of the primary and extended missions are shown in Figure 1.  We note that on PJ34, the orbital period was reduced from 53 days to 43-44 days. It will be reduced shortly after this meeting on PJ45 to 38 days and again on PJ57 to ~33 days.</p> <p><img src="" alt="" width="1015" height="914" /></p> <p><em>Figure 1. Progression of Juno orbits viewed from above Jupiter’s north pole with respect to local time of day. “PJ” designates a “perijove”, the closest approach to Jupiter on each numbered orbit. Following a Ganymede flyby on PJ34 (green orbit), the orbital period decreased from 53 days to 43-44 days (green + blue orbits). The “Great Blue Spot” (blue) orbits map an isolated patch of intense magnetic field. Following a close Europa flyby on PJ45 (aqua orbit), the period will decrease to ~38 days (orange orbits). Following close flybys of Io on PJ57 and PJ58 (black orbits) the period will decrease  to ~33 days (red orbits). In reflected sunlight, Jupiter will mostly appear as a crescent at perijoves following PJ58. </em></p> <p>Some characteristics of perijoves of the extended mission are shown in Table 1. We caution that while the day of year for the perijoves is reasonably fixed, the exact times may change by hours in either direction and the longitudes will change accordingly.  Timing for later orbits up to PJ76, may be affected by currently unmodeled anomalies in satellite masses that could change dates and times.</p> <p><img src="" alt="" width="1061" height="597" /></p> <p><em>Figure 2</em><em>.</em><em> Expected latitudes and longitudes to be measured by the 20 radio occultations of the Juno spacecraft between PJ52 and PJ77. Locations of ingress lie largely in the northern hemisphere - locations of egress in the southern hemisphere. Locations of the Galileo Probe and Voyager-1 radio occultations are also shown for reference. </em></p> <p><strong>Role of Amateur Astronomers</strong></p> <p>We’ve noted in the past at previous EPSC meetings how amateurs can contribute to the Juno mission via their collective world-wide 24/7 coverage of Jupiter. This applies also to the cadre of professional astronomers supporting the Juno mission and its reconnaissance of  the Jupiter system over a broad spectral range. In the past, these have alerted observers to strong interactions between the Great Red Spot and smaller anticyclones (Sanchez-Lavega et al. 2021. <em>J. Geophys. Res</em>. <strong>126</strong>, e006686) and the occurrence and evolution of prominent and unusual vortices, such as “Clyde’s spot” (Hueso et al. 2022. <em>Icarus</em> <strong>380</strong>,114994). During the last apparition, observations were made with the NASA Infrared Telescope Facility (IRTF) that showed slow-moving bright patches in the Equatorial Zone (EZ) that were observed more continuously among the amateur community with 890-nm (“methane”) filters. We also identified an intense 5-µm spot detected using IRTF imaging that coincided with an unusually dark spot in amateur methane-filtered images. The continued tracking of outbreaks in the southern part of the North Equatorial Belt (NEB) also greatly informed the Juno team and supporting astronomers regarding the systematic longitudinal distribution of outbreaks and the range of atmospheric features they generate. A perijove-by-perijove…

<ul> <li><strong> Introduction and Summary </strong></li> </ul> <p>Jupiter’s troposphere is divided by eastward (prograding) jets into dynamical domains, which we number sequentially (Figure 1) so the highest-latitude northern domains are N4, N5 and N6 (Figure 2).  Here we describe characteristics of these domains with short- and long-term tracking of features that can be identified in JunoCam images.  Anticyclonic white ovals (AWOs) and cyclonic folded filamentary regions (FFRs) were tracked in 2021 and earlier years, using amateur images (analysed in the JUPOS project; e.g. Figure 3) and JunoCam maps (from the imager on NASA’s Juno orbiter; e.g. Figure 4) and several Hubble maps (from the OPAL project: ref.1).</p> <p>The N6 domain is narrow and corresponds to a largely bland zone in JunoCam maps; all features in it are rapidly prograding. The N4 and N5 domains are broad and chaotic with numerous large FFRs and smaller vortices. Their zonal wind profiles (ZWPs) are dominated by the drifts of AWOs and FFRs, but faster retrograde winds exist in the FFRs.  Northerly AWOs have rapid prograde drifts, but these often change suddenly, sometimes due to interactions with FFRs or with other AWOs.  Most remarkably, in 2021-22 we have one or (very likely) two examples of AWOs moving south to cross prograde jets: one from the N4 domain and one from the N3 domain. </p> <p> </p> <ul> <li><strong> Zonal drift profiles</strong></li> </ul> <p>Previous spacecraft ZWPs have revealed the overall pattern of the domains: in both N4 and N5, the ZWP is ‘blunt’ with a broad retrograde flow (Figure 1). The Cassini polar movie, and our long-term ground-based analysis [ref.2], suggested that this represents the bulk motion of the rapidly-changing FFRs, and this is confirmed by tracking features in 2021.  The mean speeds in L3 are: in N4, +14 deg/30d;  in N5, +20 deg/30d.  Faster retrograde winds exist in the FFRs.  Conversely, AWOs have fast prograding drifts when in the northern part of each domain, but steady retrograding drifts in the southern part, where they often wander in latitude (especially in N4).  The largest AWO, in N5, has probably been tracked for at least 3 years and often progrades with the N6 jet.  Some smaller AWOs are also long-lived, while others appear and disappear within months.</p> <p> </p> <ul> <li><strong> Influences on the zonal drifts</strong></li> </ul> <p>In both N4 and N5, AWOs often undergo sudden large changes in their latitude and drift rate  (Figure 3) – just as in the N2, S3 & S4 domains.  Decelerations are sometimes due to the AWO encountering a FFR, according to examples in the Cassini polar movie and long-term ground-based analysis combined with Hubble maps [ref.2].  Accelerations may sometimes be due to the AWO encountering a smaller white spot.  AWOs sometimes pass each other in different latitudes unperturbed, but sometimes their mutual interactions can lead to mergers, or cause one or both to change latitude and speed. In 2021, a pair in N5 rebounded exchang-ing tracks, and other interactions may have propelled a N4 and a N3 AWO southwards to cross the jet.</p> <p> </p> <ul> <li><strong> AWOs crossing prograde jets</strong></li> </ul> <p>Coherent circulations almost never cross prograde jets on Jupiter, but ground-based data has demonstrated two previous instances where a N4 AWO crossed the N4 jet into the N3 domain, and in 2021-22 there was probably a third such event, captured in JunoCam images.  N4-AWO-A swung rapidly southwards after it approached N4-AWO-B (Figures 3 & 4), and was last seen at PJ39, straddling the N4 jet and split into two lobes (Figure 4).</p> <p>Likewise, a N3-AWO swung southwards and crossed the N3 jet into the NNTZ – the first time that a spot has been seen to cross a prograde jet other than the N4 jet.</p> <p> </p> <ul> <li><strong> Cloud textures</strong></li> </ul> <p>JunoCam provides unprecedented resolution on the cloud-tops in this region, revealing features such as ‘pop-up clouds’; these are small, very bright white clouds only ten(s) of km across, projecting above the main cloud deck [ref.3], seen in many locations including AWOs, FFRs, and linear white cloud bands outside the main circulations (Figure 5).  AWOs have thick white cloud cover with spiral streaking and scattered pop-up clouds. There are also much smaller vortices, both anticyclonic and cyclonic; the latter include…

<p>A complex series of high-altitude clouds and hazes have been unveiled by images from the Juno mission’s JunoCam instrument. They appear to be ubiquitous at higher latitudes in both of Jupiter’s hemispheres but are particularly pronounced in the north. Juno’s polar orbit and JunoCam’s filter centered on the 889-nm absorption band of methane make JunoCam uniquely suited to observing high-altitude polar features. Among these are the North and South Polar Hoods, which JunoCam’s methane-band filter reveals in greater detail than from the Earth, together with bright and dark haze bands. These bright and dark bands commonly appear together in bundles, indicating vertical structure in widespread haze layers. Some bright hazes near the terminator exhibit an apparent color dispersion, appearing bluish on the side generally in the direction of illumination and reddish on the other, an effect that is consistent with more efficient scattering by shorter-wavelength light. The morphology of the observed haze bands appears to be quite different from the well-known zonal wind profile affecting the main cloud deck. On the other hand, some, including a semi-persistent long band of haze near the South Pole, are related to the locations of underlying cyclones and chaotic cyclonic features known as folded filamentary regions. Our high-resolution observations of Jupiter’s limb have revealed hazes, some continuous with the lower atmosphere and others that are singly and doubly detached.  Toward high northern latitudes, these limb hazes become completely opaque.</p>

<p>The Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA Juno mission to Jupiter) includes an infrared spectrometer covering the 2.0–5.0 μm range. After reviewing the main results on the conditions of upper troposhere derived from the solar-dominated 2.0–3.2 μm spectral range and presented in Grassi et al. 2021, we focus our discussion on open modeling issues and recent attempts to study these altitudes from data in the thermal-dominated 4.0-5.0 μm spectral range. We present also the results of an automatic classification of data performed on the basis of the HDBSCAN algorithm (McInnes et al. 2017). We show that similar spatial patterns are obtained either considering the coefficents of a PCA performed directly on spectra or on the physical parameters (clouds altitude, haze thickness) retrieved by the algorithm adopted in Grassi et al. 2021.</p><p> </p><p>Grassi et al. 2021   d<span>oi:</span>10.1093/mnras/stab740</p><p>McInnes et al. 2017   d<span>oi:10.21105/joss.00205</span></p><p> </p>

<p>Amateur astronomy of the Solar System is living a golden age with major contributions to modern planetary science. These contributions cover a wide spectrum of topics that range from the discovery of impacts in Jupiter [1-2], to the observation of stellar occultations by minor bodies [3-4], the characterization of unexpected high-atmospheric events in Mars [5], or the characterization of giant storms on Jupiter [6] and Saturn [7-8]. Besides these examples of high-profile publications, there is an increasing number of amateur contributions to dozens of studies of planetary atmospheres and countless contributions to the study of minor bodies. While we focus here in the role of amateur astronomy observations of planetary atmospheres, we also recognize the varied and healthy professional and amateur collaborations in other areas of solar system astronomy.</p> <p>The reasons behind this golden age lie in the two sides of the collaboration: On the side of amateur astronomers, many of them use very efficient detectors and advanced software tools, and they are highly connected at an international level. Thus, they provide high-quality observations on a regular basis to professional astronomers, or have strong analysis teams like the JUPOS team as an example (http://jupos.privat.t-online.de/index.htm). These frequent amateur observations provide essential monitoring of the temporal evolution of planetary atmospheres. On the other side, professional astronomers are aware of the potential of these observations and actively seek the collaboration of amateur astronomers and citizen scientists. A key case in this regard is NASA’s Juno mission to the giant planet Jupiter, and its large-scale collaboration around the JunoCam instrument on the mission Juno website: https://www.missionjuno.swri.edu/. The mission has been recently extended until 2025 and details of the contribution of amateur observers to this new mission scenario are presented by Orton et al. in session ODAA5 in this meeting. Other examples of professionals seeking a global collaboration with amateurs are the various professional and amateur astronomy services and workshops organized by research projects like the Europlanet 2020 Research Infrastructure (2016-2019) and Europlanet 2024 Research Infrastructure (2020-2024).</p> <p>We anticipate that the trend of amateur astronomy playing an important role in providing additional data sets to space missions will continue to grow and we advocate for the early establishment of such collaborations.  We review some of the elements that have made the collaboration of amateur astronomers with the Juno mission so fruitful for both parties and how this collaboration has grown beyond Jupiter into enhanced collaborations in other fields through networking amateur astronomers and providing a successful example to other fields.</p> <p>We also discuss future ground-based high-resolution amateur observations of Solar System planets in support of future missions. These include the James Webb Space Telescope observations of planets (launch in October 2021), ESA’s Jupiter Icy moons Explorer (JUICE, launching in 2022) and NASA’s Europa Clipper missions to the Jupiter system in the early 2030s, the in situ exploration of Saturn’s moon Titan by the Dragonfly mission (NASA) in 2034, the Envision mission to Venus (if selected by ESA), and possible future missions to the Icy Giants Uranus and Neptune. Each of these ambitious missions will benefit from the strong partnership between amateur and professional planetary scientists. The first in this line is the JWST observations of Giant planets to be conducted in 2022 (see Fletcher et al. in session OPS3 in this conference).</p> <p>Finally, we also show some professional and amateur networking elements developed under the umbrella of the Europlanet projects, including the recently launched Europlanet Telescope Network (https://bit.ly/2Br5LDt), and we present possible scenarios for future pro-am collaborations beyond the end of the Europlanet 2024 project.</p> <p> </p> <p><strong>Acknowledgements</strong></p> <p><em>Part of this research has been supported by Europlanet 2024 RI. Europlanet 2024 RI has received funding from the European Union’s Horizon 2020 research and innovation programme under grant…

Dr. G. Randall Gladstone (CoI) Southwest Research Institute rgladstone@swri.edu Prof. John T. Clarke (CoI) (AdminUSPI) Boston University jclarke@bu.edu Dr. Bertrand Bonfond (CoI) (ESA Member) Universite de Liege b.bonfond@ulg.ac.be Prof. Jean-Claude M. Gerard (CoI) (ESA Member) Universite de Liege jc.gerard@ulg.ac.be Dr. Aikaterini Radioti (CoI) (ESA Member) Universite de Liege a.radioti@ulg.ac.be Dr. Jonathan David Nichols (CoI) (ESA Member) University of Leicester jdn4@le.ac.uk Dr. Emma J. Bunce (CoI) (ESA Member) University of Leicester ejb10@ion.le.ac.uk Dr. Lorenz Roth (CoI) (ESA Member) Royal Institute of Technology lorenzr@kth.se Dr. Joachim Saur (CoI) (ESA Member) Universitat zu Koeln saur@geo.uni-koeln.de Dr. Tomoki Kimura (CoI) RIKEN Wako Institute tomoki.kimura@riken.jp Dr. Glenn S. Orton (CoI) Jet Propulsion Laboratory glenn.s.orton@jpl.nasa.gov Dr. Sarah V. Badman (CoI) (ESA Member) Lancaster University s.badman@lancaster.ac.uk Dr. Barry Mauk (CoI) The Johns Hopkins Uni...

Juno’s Ultraviolet Spectrograph (Juno-UVS) has observed the Jovian aurora during eight perijove passes. UVS typically observes Jupiter for 10 hours centered on closest approach in a series of swaths, with one swath per Juno spin (~30s). During this period the spacecraft range to Jupiter’s aurora decreases from ~6 RJ to ~0.3 RJ (or less) in the north, and then reverses this in the south, so that spatial resolution changes dramatically. A scan mirror is used to target different features or raster across the entire auroral region. Juno-UVS observes a particular location for roughly 17 ms/swath, so the series of swaths provide snapshots of ultraviolet auroral brightness and color. A variety of forms and activity levels are represented in the Juno-UVS data–some have been described before with HST observations, but others are new. One interesting result is that the color ratio, often used as a proxy for energetic particle precipitation, may instead (in certain regions) indicate excitation of H2 by low-energy ionospheric electrons. Additional results from comparisons with simultaneous observations at x-ray, visible, and near-IR wavelengths will also be presented

In the proposal that follows we present a detailed concept for the science case, instrument requirements, technical design, calibration and operations, management structure, and financial plan for the Jupiter system Ultraviolet Dynamics Experiment (JUDE), which will provide an outstanding solution to the UV instrumentation requirements for the JUICE mission. The JUDE instrument will represent a novel technical capability in UV instrumentation for planetary science, and will deliver the first true UV imaging capability beyond Earth orbit. The JUDE instrument design consists of two separate channels – the imaging channel (ImaC) and the spectrograph channel (SpeC), neither of which has any moving parts. This simple combination of two autonomous channels allows a true image and a spectrum at FUV wavelengths to be obtained simultaneously, allowing science goals to be realised which are not possible with a traditional scanning-slit imaging-spectrograph design The international consortium assembled to build the JUDE instrument is formed of two institutes from two European countries, and one from the United States. Prof. Denis Grodent (Université de Liège, Belgium) will act as the PI for the entire instrument team and the ULg/CSL team will provide a substantial hardware contribution to the instrument in the form of the optics, coatings, and Data Processing Unit (DPU). Dr Emma Bunce (University of Leicester, UK) will act as Co-PI for the instrument and the UoL team will supply the Micro-Channel Plate (MCP) detectors and read-out electronics. Prof. John Clarke (Co-I) of Boston University, USA will provide the grating element for the spectral channel of the instrument, in addition to instrument calibration activities. The science Co-Is are gathered from multiple institutes/nations including Belgium, UK, Germany, Italy, and the United States (see Part 1 for the full team list). Collectively, the team have decades of expertise in the areas of outer planet magnetospheres, planetary auroral and atmospheric emissions and surface UV observations from multiple platforms including Cassini UVIS, Juno UVS, Hubble Space Telescope, and numerous terrestrial missions. The team also have roles on non-UV instruments which will maximise the interpretation of the JUDE data. The two instrument channels are built on proven and robust technology with much flight heritage (e.g. Juno, Cassini, BepiColombo, IMAGE, ROSAT, Chandra, Voyager, Freja, DE-1, Swift). More specifically, the optics and focal plane detector proposed for the JUDE instrument are widely based on previous designs by CSL, at the ULg and UoL, for the FUV Spectro-Imager on the NASA IMAGE spacecraft, the UV Spectrograph on the NASA Juno mission to Jupiter, and the ROSAT Wide Field Camera. The data return from the instrument will greatly benefit the European and international science communities in planetary and terrestrial sciences, and the knowledge obtained will be generally applicable to broader astrophysics disciplines (e.g. extrasolar planetary physics). In answering the UV science objectives for the JUICE mission the JUDE instrument will clearly address the ESA Cosmic Vision Themes 1: What are the conditions for planet formation and the emergence of life? and 2: How does the Solar System work? The JUDE images (in particular) provide a clear path towards a high-level related programme of education and public outreach which the JUDE team are well equipped and keen to exploit. The JUDE instrument will contribute to all of the UV-related science objectives of JUICE, plus additional science objectives not listed in the Science Requirements Matrix. - At Ganymede and other moons (Europa and Callisto) JUDE will contribute directly to breakthroughs in the following scientific areas: 1) the characterisation of local environment, specifically through the first investigation of the morphology and variation of Ganymede’s aurora. A clear understanding of the auroral and atmospheric emissions at Ganymede will provide vital information on their formation mechanisms and will contribute to studies of the interaction of the Ganymede magnetosphere with Jupiter’s magnetosphere; 2) the first detailed observations of the satellites’ atmospheric (exosphere/ionosphere) composition and structure through measurements of their atmospheric emission and absorption spectra during multiple stellar occultation opportunities; and 3) the study of the satellites surface composition using surface reflectance measurements. The measurements at UV wavelengths are essential because they allow the study of the relationship between the satellites’ surface weathering, their atmospheres and the external environment which is mainly affected by the surrounding Jovian magnetosphere. By carefully studying processes at the surface and in the satellites’ atmospheres together, JUDE will provide the information required to distinguish between two classes of compositional heterogeneities at the satellites’ surfaces: 1)…

Cassini's Ultraviolet Imaging Spectrograph (UVIS) has completed a year of study of Saturn's atmosphere and auroras. Two long slit spectral channels are used to obtain EUV data from 56.3-118.2 nm and FUV data from 111.5-191.3 nm. 64 spatial pixels along each slit are combined with slit motion to build up spectral images of Saturn, with sufficient spatial resolution to reveal

Dynamic interactions between neutrals, ions, rings, moons and meteoroids produce a highly structured and time variable Saturn system. UVIS has detected neutral oxygen, which dominates the Saturn inner magnetosphere, in contrast to Jupiter. The O is probably the product of water physical chemistry, and derived ultimately from water ice. Observed fluctuations indicate close interactions with plasma sources. Stochastic events in

Sublimation at the ice-substrate interface with pressure build-up is an accepted mechanism for the production of fan deposits on the southern polar CO2 ice cap on Mars. Fluid dynamics modeling has been used to investigate gas outflow through vents in a CO2 slab ice. Small (5–25 m in length) fan deposits seen on the annual southern CO2 ice cap can