Planetary atmosphere observation analysis

Abstract:

The Lunar-Earth Gravitational Assist (LEGA) of 19-20 August 2024 marked the first in-flight opportunity beyond functional checks to perform MAJIS (Moons and Jupiter Imaging Spectrometer) observations on-board the ESA’s Jupiter Icy Moons Explorer (JUICE) spacecraft. This unique double flyby involved sequential close approaches to the Moon and Earth, offering an unprecedented configuration to evaluate MAJIS under high radiance, rapidly changing geometric, and operationally constrained conditions. A total of 24 hyperspectral image cubes were acquired (5 targeting the Moon and 19 the Earth) providing a dataset of approximately 7.5 Gbit. This work presents the primary goal of this observation campaign, which was to verify key aspects of MAJIS performance, including radiometric and spectral calibration, straylight behavior, geometric alignment, the use of onboard browse products, and interference tests with other JUICE instruments. This event also enabled assessment of thermal behavior and susceptibility to electromagnetic interference, and provided a first operational benchmark for MAJIS and a basis for refining future observation strategies and data analyses during JUICE’s cruise and science phases. In addition, despite limited spatial and temporal coverage of the observations, the analyses presented here and in a series of companion papers of the special issue “The first-ever lunar-Earth flyby: a unique test environment for JUICE” demonstrated the instrument’s ability to characterize mineralogical features on the Moon and atmospheric constituents on Earth. Observations include detection of mafic minerals (some associated to fresh excavated materials), thermal emission, and emissivity variations on the Moon at spatial scale of 100-200 m. Characterization of atmospheric absorption features, thermal brightness, icy cloud properties are captured for the Earth at km-scale and briefly discussed in the framework of the atmospheric biosignatures relevant to exoplanet habitability studies. Near-coincident acquisitions with other JUICE instruments and Earth-orbiting spectrometers provided valuable inter-calibration and cross-validation opportunities.

Abstract:

Abstract Intermittently sunlit areas near the lunar south pole are estimated to harbor thermal conditions permitting long‐term stability of water ice and other volatiles. They are targets for future science and exploration missions due to the combination of sunlight availability for solar power generation, and the possibility for extraction of volatiles for scientific analysis and ISRU. We construct a geodatabase of spatially co‐registered remote sensing and thermal model results, and perform a probabilistic analysis to determine the likelihood of successfully landing and operating on such locations for a quadrangular study area that bounds the 80°S parallel. In addition to water ice thermal stability, we consider factors relevant for the operation of solar‐powered landed spacecraft: visibility to the Earth, visibility to the sun, and local slope. For two scenarios representing sets of most‐ and least‐constrained landing site requirements, we find that circular landing ellipse diameters of ∼0.9 and 2.6 km, respectively, would allow to target available compliant terrains with 100% success. We quantify the reduction in success probability with increasing landing ellipse size. Further, we explore the distributions of geometric properties of compliant areas, and identify three sites of interest that support large areas of compliant terrain: near De Gerlache crater, near Shackleton crater, and Mons Mouton (informally named as Leibnitz‐β massif). This study is provided to support planning for future lunar missions. Plain Language Summary Researchers have identified areas near the lunar poles that receive occasional sunlight and could keep water ice and other resources stable over a long period of time. These spots are valuable for future lunar missions since they could provide solar power and possibly resources such as water for scientific study and on‐site use. To assess potential landing sites in the south polar region, we created a database combining remote sensing and thermal data set, then used it to calculate the likelihood of successful landing on accessible terrains with stable water ice conditions from the 80°S to the South Pole. The study looked at factors critical for solar‐powered landers: the terrain's visibility to Earth (for communication), sunlight access, and the slope of the ground. We analyzed two scenarios with different landing precisions. We found that landing areas with diameters of about 0.9 and 2.6 km could ensure a 100% success rate under the most‐ and least‐constrained scenarios, respectively. Larger landing areas decreased the success probability. We also mapped the physical characteristics of ideal areas and highlighted three promising locations near De Gerlache crater, Shackleton crater, and Mons Mouton. Key Points We identify intermittently sunlit areas that permit long‐term stability of sub‐surface water ice, and accessible by landed missions “Compliant terrains” in two scenarios range from 13,071 km² (least constrained) to 290 km² (most constrained) in the south polar region For areas ≥80°S, we recommend sub‐km landing precision for missions with success criteria involving exploration of lunar polar water ice

Abstract:

The aerosol scheme for Jupiter’s upper hazes and clouds is still debated to this day, for the Crème Brûlée aerosol scheme has trouble in fitting some specific Jovian atmospheric features (Braude et al., 2020; Dahl et al., 2021). We analyse observations of Jupiter acquired with CARMENES in 2019, from visible to near infrared (0.52–1.71μm), to test three competing aerosols schemes. These observations are unique due to their spectral coverage with both high spatial and spectral resolutions, paving the way for future observations of Solar System objects. We used a model with two blue wavelength attenuating hazes (chromophores) by Anguiano-Arteaga et al., (2021); Anguiano-Arteaga et al., (2023), a model that has a single blue attenuating haze by Braude et al., (2020) and a model where the blue attenuating haze is physically constrained in a thin layer (“Crème Brûlée model”) with a more up to date parameter values from Pérez-Hoyos et al., (2020). We grouped the observations into 5 regions of the atmosphere of Jupiter and performed a Minnaert limb-darkening approximation, producing synthetic spectra at 0° and 61.45° zenith angles for each. We found that the properties of the highest aerosol layer dominate the fit to the observations, with particle size (Models A and B) and cloud base abundance (Models A and C) being the most influential parameters. We found that the extended chromophore model from Braude et al., (2020) fits the observations better than the other two models. However, none of the tested schemes fully reproduce the data, as all yield X²/N_free values greater than unity, indicating limitations in the current aerosol parametrisations. These results suggest that a consistent characterisation of Jovian aerosols requires models constrained by a broader spectral range, including ultraviolet observations sensitive to chromophore absorption and thermal infrared data probing deeper cloud layers.

Abstract:

Mars Express (MEX) is one of the most productive planetary missions of the European Space Agency (ESA). This low cost (∼150 M€) mission has been instrumental in shaping the planetary community in Europe and has contributed to paving the way for many subsequent ESA endeavours. During more than two decades, Mars Express has collected a wealth of data in all disciplines of Martian science. This paper concludes the Topical Collection “Mars Express: Pioneering Two Decades of European Science and Exploration of Mars” prepared under the auspices of the International Space Science Institute. It briefly describes various aspects of the mission (leaving details to dedicated articles), summarizes the major science achievements, discusses the lessons learned from 20 years of Mars Express operations, and bridges with future Mars science and exploration.

Abstract:

Plain Language Summary: Hydrogen chloride is a gas emitted by volcanoes on Earth. It has been hunted on Mars as a sign of recent volcanic activity, and was found with the ExoMars Trace Gas Orbiter (TGO), whose main objective is to find rare gases in the Martian atmosphere that tell us about biological or geological activity there. This commentary examines the recent results presented by Faggi et al. (2025), https://doi.org/10.1029/2025je009105 on a campaign to measure HCl in the Martian atmosphere from the Earth. From a telescope on Earth, the measurements cover the whole surface of Mars revealing how HCl is distributed and how that changes over a year. Here, we discuss the context of these results and their implications for chlorine deposits seen on the surface.