At the beginning of the next decade, the Europa Clipper Flight System will enter orbit around Jupiter and, over a four-year period, will fly by Europa nearly 50 times to explore the habitability of this planet’s moon Europa. The Flight System comprises (1) the Propulsion Module, which provides the thermally-controlled spacecraft structure, propulsion subsystem, and solar array; (2) the Avionics Module, which enables spacecraft guidance, navigation, and control operations, provides power conditioning and computer resources which stores and prioritizes science data for downlink; (3) the Radio-Frequency Module, which provides telemetry uplink and science data downlink capabilities; and (4) a highly capable suite of remote-sensing and in-situ instruments to achieve the science objectives of the mission. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments comprise the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. The mission is presently in the assembly, testing, and launch operations (ATLO) phase. The Propulsion and RF Modules have been delivered from the Johns Hopkins Applied Physics Laboratory (APL) to the Jet Propulsion Laboratory (JPL). The flight system integration and environmental testing has been completed at the Jet Propulsion Laboratory. The flight system is presently undergoing a series of operations tests. In May 2024, it will be shipped to Kennedy Space Center, where it will be integrated with the solar array, which was delivered to the location earlier this year. The launch period begins on 10 October 2024, and once lifted off, the Europa Clipper will be cruising to the Jupiter System with gravity assists by Mars followed by Earth on the way. Go Europa Clipper!

Spiked, icy features, akin to the ‘penitentes’ on Earth [1], have been found on other airless bodies in the solar system as well, such as the 'bladed terrains' of Pluto [2] and the 'spires' of Callisto [3]. These features, thought to be formed due to sublimation erosion, are present in young, crater-less regions and hence represent an active response of the surfaces of these bodies to changing seasonal and climatic conditions. Interestingly, penitente formation has also been hypothesized on Europa [4], albeit the feasibility of that process on Europa has been questioned [5]. A fundamental limitation of testing this hypothesis for Europa is the lack of images at the resolution of the proposed penitente features (~ 15 m), unlike the images of the bladed terrains of Pluto from New Horizons and spires of Callisto from Galileo which clearly show these features. Photometric roughness models peer below the resolution limit of the camera to offer a glimpse of any surface roughness that is in the geometric optics limit. Our roughness model [6], which has been successfully fit to a range of planetary bodies [7,8], will enable us to probe the surface roughness of Europa and test the penitente-hypothesis. We are locating Galileo images from the equatorial regions of Europa (within an equatorial zone restricted to ±24° where they are hypothesized to exist) and extracting scans of specific intensity (I/F) with backplanes of geometric coordinates. We will fit these I/F curves with our photometric model to derive roughness values, which will be compared to the proposed roughness of ~ 60° [4]. This predicted roughness is very high, so its effect on the light reflected from the surface should be easily detectable. To get a useful point of comparison for the roughness values we obtain for Europa, we will also perform a roughness analysis of the spires of Callisto, which are in a similar size regime of ~ 100 m. [1] Claudin, P. et al. (2015), Phys. Rev. E, 92(3), 033015; [2] Moore, J., et al. 2018, Icarus 300, 129-144, [3] Howard, A. D., & Moore, J. M. (2008). GRL, 35(3), L03203 [4] Hobley, D.E.J. et al. (2018). Nat. Geosci., 11(12), 901-904. [5] Hand, K.P. et al. ( 2020). Nat. Geosci., 13(1), 17-19. [6] Buratti, B. J., & J. Veverka (1985), Icarus 64, 320-328; [7] Buratti, B. J. et al. (2006). Planet. & Space Sci. 54, 1498-1509 [8] Lee, J. et al. (2010), Icarus 206, 623-630.

NASA’s Europa Clipper spacecraft successfully launched on 14 October 2024, on its interplanetary journey to Jupiter, where it will repeatedly encounter Europa during low-altitude (generally 25–100 km) flybys designed to enable exploration of the satellite and investigate its habitability. Europa Clipper’s 5.5 yr cruise includes gravity assists at Mars (1 March 2025) and Earth (1 December 2026). The spacecraft will enter orbit around Jupiter (11 April 2030) and will perform 49 science flybys of Europa over a 4.3-yr Jovian tour.To explore Europa as an integrated system and achieve a complete picture of its habitability, the Europa Clipper mission has three main science objectives: Characterization of: (1) the ice shell and ocean including their heterogeneity, properties, and surface–ice–ocean exchange; (2) Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) Europa’s geology including surface features and localities of high science interest. Additionally, several cross-cutting science topics will be investigated through searching for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. These science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS) consisting of a wide and a narrow angle camera (WAC, NAC), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be obtained using the spacecraft’s telecommunication system, and valuable scientific data will also be acquired by the spacecraft’s radiation monitoring system.As of this writing, the spacecraft is performing extremely well on its way toward the Mars gravity assist. Deployments of the ECM boom and REASON antennas has been successful. All initial subsystem and instrument functional checkouts are complete and also have been a success. The Europa Clipper team is nearing completion of publication of a set of manuscripts in a topical collection of Space Science Reviews, and the science team continues to work towards optimizing science return through preparation of the mission’s Strategic Science Planning Guide. Joint discussions continue on potential opportunities for unique collaborative science with ESA’s JUpiter ICy moons Explorer (JUICE) mission, which will overlap in its tour period at Jupiter.This work is supported by NASA through the Europa Clipper Project.

Europa's surface is one of the most compelling mysteries of the solar system. It displays complex photometric behavior driven by its rich geology and interaction with the Jovian environment. Cryovolcanism across the surface creates frequent resurfacing, which is competing with external plasma and meteorite bombardment. This study revisits data from Galileo's Near-Infrared Mapping Spectrometer to conduct a comprehensive, multiwavelength photometric analysis of selected regions across Europa's surface. Using a Bayesian inversion framework and the Hapke photometric model, we estimate key surface parameters-including single scattering albedo, macroscopic roughness, and phase function properties-across three geologically diverse regions. Results show a significant link between macroscopic roughness and single scattering albedo, where values of theta will sharply change when the single scattering albedo becomes too high (in this study, we found this transition to happen at omega approximate to 0.8). This is caused by multiple scattering that becomes too significant at a certain brightness and results in the illumination of shadows. This effect is potentially leading to systematic underestimation of roughness in traditional photometric modeling focused on the visible wavelengths. In addition, we observe increasing forward scattering at longer wavelengths, suggesting changes in internal scattering properties or composition. These findings highlight the need to account for albedo-driven photometric behavior in future analyses. This work is important to inform planetary data analysis in general but particularly for the planning of remote-sensing observations of the upcoming missions bound to the Jovian system-NASA's Europa Clipper and ESA's JUICE.

Scheduled to launch in October 2024, NASA’s Europa Clipper will set out on a journey to explore the habitability of Jupiter’s icy ocean world Europa. After a 5.5 yr cruise that includes gravity assists at Mars and Earth, the spacecraft will enter orbit around Jupiter and will perform nearly 50 flybys of Europa over a four-year period. To explore Europa as an integrated system and achieve a complete picture of its habitability, the Europa Clipper mission has three main science objectives to characterize: (1) the ice shell and ocean including their heterogeneity, properties, and surface–ice–ocean exchange; (2) Europa’s composition including any non-ice materials on the surface and in the atmosphere, and any carbon-containing compounds; and (3) Europa’s geology including surface features and localities of high science interest. Additionally, several cross-cutting science topics will be investigated through searching for any current or recent activity in the form of thermal anomalies and plumes, performing geodetic and radiation measurements, and assessing high-resolution, co-located observations at select sites to provide reconnaissance for a potential future landed mission. These science objectives will be accomplished using a highly capable suite of remote-sensing and in-situ instruments. The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS) consisting of a wide and a narrow angle camera (WAC, NAC), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be obtained using the spacecraft's telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. Assembly, test, and launch operations (ATLO) of the Europa Clipper spacecraft are progressing well, and the flight system integration and environmental testing has been completed at the Jet Propulsion Laboratory. Currently, the flight system is undergoing operations testing, and in May 2024, the spacecraft will be shipped to NASA’s Kennedy Space Center at Cape Canaveral, Florida. There, the remaining integration activities will occur for the solar array and REASON antennas followed by final flight system tests. The launch period begins on 10 October 2024. To provide details on the mission’s instruments and planned investigations, the Europa Clipper science team is publishing manuscripts in a special issue of Space Science Reviews, and the team continues to work towards optimizing science return through preparation of the mission’s Strategic Science Planning Guide. As well, collaborative science opportunities with ESA’s JUpiter ICy moons Explorer (JUICE) mission, which will overlap in its tour period at Jupiter and make observations of Europa, are being discussed informally among the science teams. Onward to Europa!

Features that change in appearance between different NASA New Horizons images of Pluto are analyzed. Contrast reversal features (CRs) appear to transition from darker to brighter than their surroundings, more likely due to changes of imaging geometry, specifically increasing solar phase angle, than temporal change. Contrast emergent features (CEs) are not apparent in low- and intermediate-solar-phase-angle images but brighter than their surroundings in high-solar-phase-angle image(s), also more likely due to the increase of solar phase angle than temporal change. Hypotheses for Pluto’s CRs and CEs include plumes, clouds, wind streaks, snow, frost, precipitated haze, lags, pits, glints, slopes, and particle size, compaction, and geometric effects. The CRs and CEs could be on and/or above Pluto’s surface and/or within its shallow subsurface. These hypotheses are investigated via mapping, color, morphology, photometry, and comparison with Triton’s fans. Pluto’s CRs and CEs are likely different manifestations of the same or similar phenomena. They are likely not diffuse deposits of Pluto’s dark red equatorial material(s) on or above or within volatile-ice-rich regions, sunglints, or geometric effects from spatially resolved slopes. They are consistent with less backward-scattering and more forward-scattering surfaces and shallow subsurfaces than their surroundings, as well as optically thin, preferentially forward scattering between the surface and global haze, including atmospheric (e.g., cloud) and surface-coating (e.g., condensation deposit) features. Surface and/or shallow subsurface features, possibly atmospheric derived, are favored over atmospheric features.

AbstractThe Near-Earth Object Surveillance Mission (NEOSM) will provide unprecedented detection, tracking and characterization of Near-Earth Objects (NEOs) using high-cadence imaging from a space-based infrared telescope. Planning for the NEOSM requires an accurate model of the solar system’s small body populations in order to develop efficient operational survey strategies and to assess survey performance once in-flight operations have commenced. The NEOSM Investigation Team is currently developing the Reference Small Body Population Model (RSBPM; [1]) that will contain the current best estimates of the dynamical and physical properties of the solar system’s small body populations. Development of the RSBPM will be completed before the NEOSM launch, and the finished product will be peer-reviewed to ensure accuracy. Once the survey begins, we will compare predictions based on the RSBPM to actual observational measurements to calculate the efficiency of the survey, and thus de-bias the survey to properly characterize each population in order to assess Earth impact risks. We present here an update to the methods of incorporating comets into the RSBPM, with particular focus on accurately incorporating dust and CO+CO2 gas comae activity behaviors. A better understanding of these physical characteristics are relevant for planetary defense (e.g., determining nuclei diameters).The high abundance of volatile ices (e.g., H2O, CO, CO2) present in comet nuclei drives outgassing and dust lofting when the surface material is exposed to the Sun, generating comae and tails. While high-cadence and long-baseline observational campaigns producing physical characterization of nuclei and comae exist for a few comets (e.g. 1P/Halley, 9P/Tempel, 67P/Churyumov-Gerasimenko, C/1995 O1 (Hale-Bopp), C/2012 S1 (ISON)) and have allowed determination of single-apparition secular light curves, predictions for the behaviors of an individual comet are notoriously difficult due to the possibility of outbursts, fragmentation events, complete nucleus disintegration and seasonal effects. This high degree of uncertainty for cometary behaviors introduces complications for modeling the brightening trends for individual comets as compared to those for the asteroid populations. Fortunately, characterizing the behaviors of comets in the infrared as an ensemble population is a somewhat more tractable problem. Previous (e.g., COBE [2], AKARI [3], Spitzer [4]) and ongoing surveys (e.g, Pan-STARRS [5], Zwicky Transient Facility [6], ATLAS [7], WISE/NEOWISE [8]) detecting large numbers of comets in the infrared are allowing a framework through which an individual comet’s activity behaviors can be estimated based on behavior trends in infrared emission of the larger ensemble. We are utilizing derived ensemble properties from these observational campaigns to develop a recipe for best simulating the morphological and photometric behaviors for the solar system’s comet populations.NEOSM will utilize a space-based 50-cm aperture infrared-optimized telescope located at the Sun-Earth L1 Lagrange position. It will contain a single instrument with a dual-channel infrared imaging camera that will survey the sky in bandpasses at 4-5.2 microns (denoted NC1) and 6-10 microns (denoted NC2). NC1 images of comets will mostly contain thermal emission (for comets within ~3 au of the Sun) from the nucleus and any dust coma/tail/trail. Additionally, the bandpass of NC1 covers the CO2 gas ν3 vibrational mode emission band centered at 4.26 microns and the CO gas vibrational mode emission band centered at 4.67 microns, which will allow detection of a comet’s combined CO+CO2 gas coma. This method of detecting such cometary volatiles via broadband imaging has had much success in the past with Spitzer (e.g. [4, 9]) and WISE/NEOWISE (e.g. [10, 11]). The longer wavelength NC2 images of comets will measure thermal emission from nuclei and dust. Because of the particular bandpasses of NC1 and NC2 we are currently focusing on developing methods of modeling cometary activity behaviors utilizing derived (1) nuclei cumulative size distributions, (2) dust activity behaviors as characterized by empirical trends of the εfρ parameter and (3) CO and CO2 gas comae trends based on the previously mentioned past and ongoing surveys. Future efforts by the NEOSM Investigation Team will focus on incorporation of other characteristic cometary phenomena (e.g., dust tails and trails) to help refine expected detection efficiencies and coma and/or tail flux removal for robust nucleus size estimation.AcknowledgementsNEOSM is a project sponsored by NASA’s Planetary Defense Coordination Office, a division of NASA’s Planetary Science Directorate.References[1] Lilly (Schunova) et al., 2020, AAS Meeting Abstracts, 385.04.[2] Lisse et al., 2002, IAU Colloq. 181, Vol. 15, 259.[3] Ootsubo et al., 2012, ApJ, 752:15.[4] Fernandez et al., 2013, Icarus, 226, Issue 1.[5] Denneau et al., 2013, PASP, 125:926.[6] Masci et al., 2019, PASP, 131:995.[7] Tonry et al., 2018, PASP, 130:988.[8] Mainzer et al., 2011, ApJ, 731:53.[9] Kelley et al., 2013, Icarus, 225:475.[10] Bauer et al., 2015, ApJ, 814:85.[11] Bauer et al., 2017, AJ, 154:53.

COLVI related myopathies include phenotypes ranging from severe forms (Ullrich congenital muscular dystrophy) to more moderate forms (Bethlem myopathy). They result from abnormalities in the expression and/or secretion of collagen VI (COLVI), a component of the extracellular matrix which is formed by the assembly of 3 chains alpha 1, alpha 2 and alpha 3 each encoded by the COL6A1-A2-A3 genes. Their diagnosis is based on clinical criteria, muscle MRI and genetic analyses. We present the case of a patient with a typical COLVI related myopathy phenotype but for whom initial NGS panel analyzes were not conclusive. Complementary techniques of protein and transcriptional studies allowed confirming the diagnosis. Blood gDNA of the proband was sequenced on a NGS panel containing coding sequences of genes associated with retractile myopathies including COL6A1, COL6A2 and COL6A3. COLVI expression was carried out by immunostaining on fibroblasts obtained from a skin biopsy. A transcriptomic study by RNA-seq on mRNA from fibroblasts made it possible to analyze aberrant splicing of COL6A1-A2-A3. As no variant of interest was retained on the NGS panel, COLVI immunostaining on fibroblasts was carried out and showed an alteration of its secretion with absence of COLVI network. Subsequently, a transcriptomic approach by RNA-seq showed the skipping of exon 11 in the heterozygous state in COL6A1. Reanalysis of the NGS .bam files allowed characterizing the deletion consisting in a short CNV involving part of both exon 11 and intron 11 of COL6A1. Familial segregation could show this was a de novo event. Given the very evocative clinic and thanks to functional studies, we identified the causal genetic variant allowing us to confirm the diagnosis of Ullrich myopathy. This example illustrates the importance of clinician-biologist dialogue, the limits of analyzes on genomic DNA, and the complementarity of functional tests in order to reduce diagnostic wandering.

This study provides a pre-impact map of the albedo of the Double Asteroid Redirection Test (DART) target Dimorphos corrected for all the effects of viewing geometry, as well as an estimate of photometric roughness for the hemisphere imaged by DART. Other photometric properties are derived for the (65803) Didymos binary system based on DART and ground-based measurements obtained at JPL’s Table Mountain Observatory. The roughness, geometric albedo, phase curve and phase integral, and single particle phase function are typical of the S-family of asteroids. The major remaining uncertainty lies in the behavior of the phase curve below 7°. These results provide a baseline for comparison with Hera measurements, leading to an understanding of the quantitative effects of the kinetic impactor mitigation strategy.

NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 minutes, with two independent analysis methods each reporting a 1 σ uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor, β , resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos–Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense.

The goal of NASA’s Europa Clipper mission is to assess the habitability of Jupiter’s moon Europa. After entering Jupiter orbit in 2030, the flight system will collect science data while flying past Europa 49 times at typical closest approach distances of 25–100 km. The mission’s objectives are to investigate Europa’s interior (ice shell and ocean), composition, and geology; the mission will also search for and characterize any current activity including possible plumes. The science objectives will be accomplished with a payload consisting of remote sensing and in-situ instruments. Remote sensing investigations cover the ultraviolet, visible, near infrared, and thermal infrared wavelength ranges of the electromagnetic spectrum, as well as an ice-penetrating radar. In-situ investigations measure the magnetic field, dust grains, neutral gas, and plasma surrounding Europa. Gravity science will be achieved using the telecommunication system, and a radiation monitoring engineering subsystem will provide complementary science data. The flight system is designed to enable all science instruments to operate and gather data simultaneously. Mission planning and operations are guided by scientific requirements and observation strategies, while appropriate updates to the plan will be made tactically as the instruments and Europa are characterized and discoveries emerge. Following collection and validation, all science data will be archived in NASA’s Planetary Data System. Communication, data sharing, and publication policies promote visibility, collaboration, and mutual interdependence across the full Europa Clipper science team, to best achieve the interdisciplinary science necessary to understand Europa.

Introduction: In October 2024, NASA’s Europa Clipper will launch on a journey to explore the habitability of Jupiter’s moon Europa. At the beginning of the next decade, the spacecraft will orbit Jupiter, flying by Europa nearly 50 times over a four-year period to: (1) Characterize the ice shell and any subsurface water, including their heterogeneity, ocean properties, and the nature of surface-ice- exchange; (2) understand the habitability of Europa’s ocean through composition and chemistry; and (3) understand the formation of surface features, including sites of recent or current activity, and characterize high science interest localities. In addition, the search for current activity cross-cuts these three principal science objectives.Flight System: The Flight System (Figure 1) comprises the Propulsion Module, which provides the thermally-controlled spacecraft structure, propulsion subsystem, and solar array (not shown); the Avionics Module, which enables spacecraft guidance, navigation, and control operations, provides power conditioning and computer resources which stores and prioritizes science data for downlink; the Radio-Frequency (RF) Module, which provides telemetry uplink and science data downlink capabilities; and a highly capable suite of remote-sensing and in-situ instruments (Figure 2) to achieve the science objectives of the mission. The spacecraft is solar-powered with large batteries for use during the flyby and playback periods, uses reaction wheels for precise attitude control, and has a bipropellant system for propulsion and coarse attitude control. The Avionics Module consists of a radiation vault, nadir platform, and secondary structures. The module supports multiple instruments, components, and elements from other modules. The vault provides radiation protection and thermal interface control to internal electronics, and mounting support for various external instruments and spacecraft components. The telecom system includes a high-gain antenna for communication at X- or Ka-band, a co-aligned medium-gain, three low-gain antennas, and three fan beam antennas.Figure 1: Europa Clipper flight systemInstrumentation: The remote sensing payload consists of the Europa Ultraviolet Spectrograph (Europa-UVS), the Europa Imaging System (EIS), the Mapping Imaging Spectrometer for Europa (MISE), the Europa Thermal Imaging System (E-THEMIS), and the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON). The in-situ instruments are the Europa Clipper Magnetometer (ECM), the Plasma Instrument for Magnetic Sounding (PIMS), the SUrface Dust Analyzer (SUDA), and the MAss Spectrometer for Planetary Exploration (MASPEX). Gravity and radio science will be achieved using the spacecraft’s telecommunication system, and valuable scientific data will be acquired by the spacecraft’s radiation monitoring system. All instruments are body mounted, and the spacecraft points the remote sensing instruments toward nadir during most of the flybys, while the in-situ instruments face the ram direction at closest approach. The MISE instrument has an internal mirror that further allows it to scan along-track to compensate for target motion when close to Europa. The narrow-angle camera has a two-axis gimbal to allow for acquisition of stereo coverage and to extend its field of regard to off-nadir targets.Figure 2: Europa Clipper suite of instrumentsMission Status: The assembly, testing, and launch operations (ATLO) phase is in its final stage. System-level testing has been completed at the Jet Propulsion Laboratory, and the flight system has been integrated with the solar array at Kennedy Space Center. The Operations and Mission Readiness Reviews have been successfully completed, and the Europa Clipper will be encapsulated in the Falcon 9 Heavy rocket in early October. The launch period begins on 10 October 2024, and once lifted off, the Europa Clipper will be cruising to the Jupiter System with gravity assists by Mars followed by Earth on the way. Go Europa Clipper!

Jupiter's icy moon, Europa, harbors a subsurface liquid water ocean; the prospect of this ocean being habitable motivates further exploration of the moon with the upcoming NASA Europa Clipper mission. Key among the mission goals is a comprehensive assessment of the moon's composition, which is essential for assessing Europa's habitability. Through powerful remote sensing and in situ investigations, the Europa Clipper mission will explore the composition of Europa's surface and subsurface, its tenuous atmosphere, and the local space environment surrounding the moon. Clues on the interior composition of Europa will be gathered through these assessments, especially in regions that may expose subsurface materials, including compelling geologic landforms or locations indicative of recent or current activity such as potential plumes. The planned reconnaissance of the icy world will constrain models that simulate the ongoing external and internal processes that act to alter its composition. This paper presents the composition-themed goals for the Europa Clipper mission, the synergistic, composition-focused investigations that will be conducted, and how the anticipated scientific return will advance our understanding of the origin, evolution, and current state of Europa.

The 27 moons of Uranus (Figure 1) are enigmatic and remain poorly understood. Voyager 2 flew by the Uranus system in 1986, collecting fascinating images of its five largest, tidally-locked ‘classical’ moons (Figure 2), while also discovering a bevy of small moons nestled in its ring system (e.g., [1]) (Figure 3). The surfaces of Uranus’ classical moons Miranda, Ariel, Umbriel, Titania, and Oberon have been modified by endogenic activity, in particular Miranda and Ariel, which exhibit substantial evidence for geologic communication between their interiors and surfaces (e.g., [1-3]) (Figure 2). The available images therefore indicate that these classical moons are candidate ocean worlds, which have, or had, liquid H2O layers beneath their icy exteriors (e.g., [3-5]). Because the Voyager 2 flyby occurred near Uranus’ southern summer solstice (subsolar latitude ~81°S), the collected images are centered near the south poles of these moons, and their northern hemispheres were largely unobservable. Furthermore, only the classical moons and the largest ring moon Puck (Figure 3) were spatially resolved by Voyager 2. The other nine ring moons Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalina, and Belinda were not resolved. Another ring moon, Perdita, was discovered via reanalysis of Voyager 2 data [6], and two more ring moons, Cupid and Mab [7,8], were discovered by space-based telescope observations. All nine known irregular satellites, Francisco, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos, and Ferdinand, were not detected by Voyager 2 and were discovered later by ground-based observations (e.g., [9-11]).Voyager 2 was not equipped with a near-infrared (NIR) mapping spectrometer, and most of what we know about the compositions of Uranus’ moons has been determined using data collected by ground and space-based telescopes. The surfaces of Uranus’ classical moons are composed of H2O ice mixed with low albedo material that could be rich in organics and silicate minerals (e.g., [12-14]). Carbon dioxide (CO2) has been detected on the classical moons, primarily on their trailing hemispheres, in particular on Ariel [15,16] (Figure 4). Spectrally red material that could be rich in organics has been detected, primarily on the leading hemispheres of these moons (e.g., [17,18]) (Figure 4). Ammonia (NH3) has possibly been detected on the classical moons and may originate from their interiors [18,19]. Although useful, these prior observations are disk-integrated, limiting our ability to constrain the distribution of surface constituents and identify links between volatile species and geologic terrains. Much less is known about the surface compositions of Uranus’ 13 ring moons and nine irregular satellites, which are mostly too faint (Vmag 19.8 - 25.8) for spectroscopic analysis using existing facilities. Spectrophotometric datasets indicate that Uranus’ ring moons have dark surfaces that show hints of H2O ice features [6]. Uranus’ irregular satellites have dark, reddish surfaces (e.g., [20]) but little else is known about their surface compositions, except for Sycorax, which shows hints of H2O ice [21].An orbiting spacecraft collecting data during close flybys of Uranus’ ring system and classical moons would reveal the surface geologies of these moons, including on their previously unobserved northern hemispheres, determine their surface compositions, and determine whether any of the classical moons are, or were, ocean worlds. Furthermore, an orbiter could spend time looking outward to characterize Uranus’ irregular satellites, providing new insight into these likely captured objects (e.g., Jewitt & Haghighipour 2007). By utilizing a Jupiter gravity assist (2030 - 2034 launch window), a mission could arrive at the Uranian system in the mid 2040’s (∼11 years flight time), using existing chemical propulsion technology [22]. This arrival time frame would allow us to observe these moons’ northern hemispheres. An orbiter making close flybys of the classical moons could search for evidence of ongoing geologic activity and characterize migration of CO2 in response to changes in subsolar heating as the Uranian system transitions into southern spring in 2050.To determine whether liquid H2O layers are present in the interiors of the classical moons, the highest priority instrument onboard an orbiter would be a magnetometer, which could detect and characterize induced magnetic fields emanating from briny subsurface oceans. Visible (VIS, 0.4 - 0.7 µm) and mid-infrared (MIR, 5 - 250 µm) cameras would also be vital to search for plume activity, hot spots, and other signs of geologic communication between the interiors and surfaces of these moons. A spectrometer (0.4 - 5 µm) would be critical for characterizing volatile species that might result from outgassing of material or recently exposed or emplaced surface deposits. The abundant evidence for geologic activity in the recent past on Ariel and Miranda likely makes them the highest priority targets for any mission that aims to characterize Uranus’ satellites.References: [1] Smith, B. A. et al. 1986, Science, 233, 43. [2] Schenk, P. M. 1991, JGR: Solid Earth, 96, 1887. [3] Beddingfield, C. B. & Cartwright, R. J. 2020, Icarus, 113687. [4] Hendrix, A. R. et al. 2019, Astrobiology, 19, 1. [5] Cartwright, R.J. et al. 2021. arXiv preprint arXiv:2105.01164. [6] Karkoschka, E. 2001, Icarus, 151, 51. [7] Showalter, M. R. & Lissauer, J. J. 2006, Science, 311, 973. [8] De Pater, I. et al. 2006, Science, 312, 92. [9] Gladman, B. J. et al. 1998, Nature, 392, 897. [10] Kavelaars, J. et al. 2004, Icarus, 169, 474. [11] Sheppard, S. S. et al. 2005, AJ, 129, 518. [12] Cruikshank, D. et al. 1977, AJ, 217, 1006. [13] Clark, R. N. & Lucey, P. G. 1984, JGR: Solid Earth, 89, 6341. [14] Brown, R. H. & Clark, R. N. 1984, Icarus, 58, 288. [15] Grundy, W. et al. 2006, Icarus, 184, 543. [16] Cartwright, R. J. et al. 2015, Icarus, 257, 428. [17] Buratti, B. J. & Mosher, J. A. 1991, Icarus, 90, 1. [18] Cartwright, R. J. et al. 2018, Icarus, 314, 210. [19] Cartwright, R. J. et al. 2020c, ApJL, 898, L22. [20] Maris, M. et al. 2007, A&A, 472, 311. [21] Romon, J. et al. 2001, A&A, 376, 310. [22] Hofstadter, M. et al. 2019, Planetary and Space Science, 177, 104680.

The Near-Earth Object (NEO) Surveyor mission is a NASA Observatory designed to discover and characterize asteroids and comets. The mission’s primary objective is to find the majority of objects large enough to cause severe regional impact damage (>140 m in effective spherical diameter) within its 5 yr baseline survey. Operating at the Sun–Earth L1 Lagrange point, the mission will survey to within 45° of the Sun in an effort to find objects in the most Earth-like orbits. The survey cadence is optimized to provide observational arcs long enough to distinguish near-Earth objects from more distant small bodies that cannot pose an impact hazard reliably. Over the course of its survey, NEO Surveyor will discover ∼200,000–300,000 new NEOs down to sizes as small as ∼10 m and thousands of comets, significantly improving our understanding of the probability of an Earth impact over the next century.

Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation 1 , 2 . Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid 1 – 3 . A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation 1 . NASA’s Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission’s target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft 4 . Although past missions have utilized impactors to investigate the properties of small bodies 5 , 6 , those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft’s autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos 7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary.

The Galileo mission to Jupiter revealed that Europa is an ocean world. The Galileo magnetometer experiment in particular provided strong evidence for a salty subsurface ocean beneath the ice shell, likely in contact with the rocky core. Within the ice shell and ocean, a number of tectonic and geodynamic processes may operate today or have operated at some point in the past, including solid ice convection, diapirism, subsumption, and interstitial lake formation. The science objectives of the Europa Clipper mission include the characterization of Europa’s interior; confirmation of the presence of a subsurface ocean; identification of constraints on the depth to this ocean, and on its salinity and thickness; and determination of processes of material exchange between the surface, ice shell, and ocean. Three broad categories of investigation are planned to interrogate different aspects of the subsurface structure and properties of the ice shell and ocean: magnetic induction, subsurface radar sounding, and tidal deformation. These investigations are supplemented by several auxiliary measurements. Alone, each of these investigations will reveal unique information. Together, the synergy between these investigations will expose the secrets of the Europan interior in unprecedented detail, an essential step in evaluating the habitability of this ocean world.

The New Horizons encounter with the Pluto system revealed Pluto to have an extremely spatially variable surface with expansive dark, bright, and intermediate terrains, refractory and volatile ices, and ongoing/recent endogenous and exogenous processes. Albedo is useful for understanding volatile transport because it quantifies absorbed solar energy; albedo may also provide insights into surface processes. Four filters of the New Horizons LORRI and MVIC imagers are used to approximate the bolometric (flux-weighted, wavelength-integrated) albedo. The bolometric hemispherical albedo (local energy balance albedo) as a function of the incidence angle of the solar illumination is measured for both Cthulhu and Sputnik Planitia, which are extensive, extreme dark and extreme bright terrains on Pluto. For both terrains, the bolometric hemispherical albedo increases by >30% from 0° to 90° incidence. The incidence-angle-average bolometric hemispherical albedo of Cthulhu is 0.12 ± 0.01, and that of Sputnik Planitia is 0.80 ± 0.06, where uncertainties are estimates based on scatter from different photometric functional approximations. The bolometric Bond albedo (global energy balance albedo) of Cthulhu is 0.12 ± 0.01, and that of Sputnik Planitia is 0.80 ± 0.07. A map of Pluto’s incidence-angle-average bolometric hemispherical albedo is produced. The incidence-angle-average bolometric hemispherical albedo, spatially averaged over areas north of ≈30° S, is ≈0.54. Pluto has three general albedo categories: (1) very low albedo southern equatorial terrains, including Cthulhu; (2) high-albedo terrains, which constitute most of Pluto’s surface; and (3) very high albedo terrains, including Sputnik Planitia. Pluto’s extraordinary albedo variability with location is also spatially sharp at some places.