The MAJIS (Moons And Jupiter Imaging Spectrometer) instrument, part of the JUICE (JUpiter ICy moons Explorer) mission, is a crucial tool for investigating the composition and dynamics of Jupiter's atmosphere, and the surfaces and exospheres of its icy moons. To optimize observational planning and assess instrument performance, we have developed a radiometric simulator that accurately models MAJIS expected signal from various Jovian system targets. This simulator incorporates instrumental parameters, the spacecraft trajectory, observational constraints, and Jupiter's radiation environment. It provides essential outputs, including Signal-to-Noise Ratio (SNR) predictions and optimized instrument settings for different observational scenarios. By simulating both radiometric performance and de-spiking strategies to mitigate the impact of Jupiter radiation belt, the tool aids in refining observation strategies throughout the MAJIS operations. Several scientific applications demonstrate the simulator capabilities, from mapping the surfaces of Ganymede and Europa to detecting exospheric emissions and atmospheric composition on Jupiter. This simulator is a critical asset for maximizing MAJIS scientific return and ensuring optimal data acquisition during MAJIS exploration of the Jovian system. Study cases are presented for illustrating the capability of the simulator to model scenarios such as high-resolution mapping of Ganymede, exosphere characterization and hotspot detection on Io and Europa. These simulations confirm the potential of MAJIS for detecting key spectral features with high signal to noise ratio so as to provide major contributions to the main goals of the mission: habitability and compositional diversity in the Jovian system.

Current models suggest the five regular moons of Uranus formed in a single stage from a primary planetary disk or a secondary impact disk. Using latest estimates of moon masses (Jacobson, 2014), we find a power-law relationship between size and density of the moons due to varying rock/ice ratios caused by fractionation processes. This relationship is better explained by mild enrichment of rock with respect to ice in the solids that aggregate to form the moons following Rayleigh law for distillation (Rayleigh, 1896) than by differential diffusion in the disk, although the two mechanisms are not exclusive. Rayleigh fractionation requires that moon composition and density reflect their order of formation in a closed-system circumplanetary disk. For Uranus, the largest and densest moons Titania and Oberon (R similar to 788 and 761 km, respectively) first formed, then the midsized Umbriel and Ariel (585 and 579 km), satellites in each pair forming simultaneously with similar composition, and finally the small rock-depleted Miranda (236 km). Fractionation likely occurred through impact vaporization during planetesimal accretion. This mechanism would add to those affecting the composition of accreting planets and moons in disks such as temporal/spatial variation of disk composition due to temperature gradients, advection, and large impacts. In the outer solar nebula, Rayleigh fractionation may account for the separation of a rock-dominated reservoir, and an ice-dominated reservoir, currently represented by CI carbonaceous chondrite/type-C asteroids and comets, respectively. Potential consequences for Uranus moons' composition are discussed.

In this study, we calculated the travel times of a thermal probe that descends through Europa's ice shell. The ice column is simplified to a conductive layer. Using a cellular automaton model, the descent of the probe was simulated by tracking temperature changes, with cell interaction dictated by heat conduction and cell state transition rules determined by cell temperatures. Validation tests, including a soil column simulation, and comparison with experimental data, support the reliability of the model. Simulations were performed with 2 different cell sizes, 19 constant probe temperatures, and 5 ice thermal conductivities. A smaller cell size ( Delta z=3 mm) produced shorter travel times (between 22 days for a probe temperature Tp=600K and similar to 4 years for Tp=280K) than a larger cell size ( Delta z=1 m), which produced travel times between 27 years ( Tp= 600K) and similar to 103 years ( Tp= 280K). The ice shell's thermal conductivity has a modest impact on descent times. The results are generally consistent with previous approaches that used more detailed probe engineering considerations. These results suggest that a probe relying solely on heat production may traverse Europa's conductive ice shell within a mission's timeframe.

Sodium chloride is expected to be found on many of the surfaces of icy moons like Europa and Ganymede. However, spectral identification remains elusive as the known NaCl-bearing phases cannot match current observations, which require higher number of water of hydration. Working at relevant conditions for icy worlds, we report the characterization of three hyperhydrated sodium chloride (SC) hydrates, and refined two crystal structures [2NaCl center dot 17H(2)O (SC8.5); NaCl center dot 13H(2)O (SC13)]. We found that the dissociation of Na+ and Cl- ions within these crystal lattices allows for the high incorporation of water molecules and thus explain their hyperhydration. This finding suggests that a great diversity of hyperhydrated crystalline phases of common salts might be found at similar conditions. Thermodynamic constraints indicate that SC8.5 is stable at room pressure below 235 K, and it could be the most abundant NaCl hydrate on icy moon surfaces like Europa, Titan, Ganymede, Callisto, Enceladus, or Ceres. The finding of these hyperhydrated structures represents a major update to the H2O-NaCl phase diagram. These hyperhydrated structures provide an explanation for the mismatch between the remote observations of the surface of Europa and Ganymede and previously available data on NaCl solids. It also underlines the urgent need for mineralogical exploration and spectral data on hyperhydrates at relevant conditions to help future icy world exploration by space missions.

The Earth-like planets and moons in our solar system have iron-rich cores, silicate mantles, and a basaltic crust. Differentiated icy moons can have a core and a mantle and an outer water-ice layer. Indirect evidence for several icy moons suggests that this ice is underlain by or includes a water-rich ocean. Similar processes are at work in the interiors of these planets and moons, including heat transport by conduction and convection, melting and volcanism, and magnetic field generation. There are significant differences in detail, though, in both bulk chemical compositions and relative volume of metal, rock and ice reservoirs. For example, the Moon has a small core [similar to 0.2 planetary radii (R-P)], whereas Mercury's is large (similar to 0.8 R-P). Planetary heat engines can operate in somewhat different ways affecting the evolution of the planetary bodies. Mercury and Ganymede have a present-day magnetic field while the core dynamo ceased to operate billions of years ago in the Moon and Mars. Planets and moons differ in tectonic style, from plate-tectonics on Earth to bodies having a stagnant outer lid and possibly solid-state convection underneath, with implications for their magmatic and atmosphere evolution. Knowledge about their deep interiors has improved considerably thanks to a multitude of planetary space missions but, in comparison with Earth, the data base is still limited. We describe methods (including experimental approaches and numerical modeling) and data (e.g., gravity field, rotational state, seismic signals, magnetic field, heat flux, and chemical compositions) used from missions and ground-based observations to explore the deep interiors, their dynamics and evolution and describe as examples Mercury, Venus, Moon, Mars, Ganymede and Enceladus.

We develop an analytical model of the Alfven wings generated by the interaction between a moon's ionosphere and its sub-Alfvenic magnetospheric environment. Our approach takes into account a realistic representation of the ionospheric Pedersen conductance profile that typically reaches a local minimum above the moon's poles and maximizes along the bundle of magnetospheric field lines tangential to the surface. By solving the equation for the electrostatic potential, we obtain expressions for various quantities characterizing the interaction, such as the number flux and energy deposition of magnetospheric plasma onto the surface, the spatial distribution of currents within the Alfven wings and associated magnetic field perturbations, as well as the Poynting flux transmitted along the wings. Our major findings are: (a) Deflection of the magnetospheric plasma around the Alfven wings can reduce the number flux onto the surface by several orders of magnitude. However, the Alfvenic interaction alone does not alter the qualitative shape of the bullseye-like precipitation pattern formed without the plasma interaction. (b) Due to the deflection of the upstream plasma, the energy deposition onto the moon's exosphere achieves its minimum near the ramside apex and maximizes along the flanks of the interaction region. (c) Even when the ionospheric conductance profile is continuous, the currents along the Alfven wings exhibit several sharp jumps. These discontinuities generate spikes in the magnetic field that are still observable at large distances to the moon. (d) The magnitude and direction of the wing-aligned currents are determined by the slope of the ionospheric conductance profile.

The quest for life on other planets is closely connected with the search for water in liquid state. Recent discoveries of deep oceans on icy moons like Europa and Enceladus have spurred an intensive discussion about how these waters can be accessed. The challenge of this endeavor lies in the unforeseeable requirements on instrumental characteristics both with respect to the scientific and technical methods. The TRIPLE/nanoAUV initiative is aiming at developing a mission concept for exploring exo-oceans and demonstrating the achievements in an earth-analogue context, exploring the ocean under the ice shield of Antarctica and lakes like Dome-C on the Antarctic continent.

Evidence of life beyond Earth may be closer than we think, given that the forthcoming missions to the jovian system will be equipped with instruments capable of probing Europa's icy surface for possible biosignatures, including chemical biomarkers, despite the strong radiation environment. Geochemical biomarkers may also exist beyond Europa on icy moons of the gas giants. Sulfur is proposed as a reliable geochemical biomarker for approved and forthcoming missions to the outer solar system. Key Words: JUICE missionClipper missionGeochemical biomarkersEuropaMoons of the ice giantsGeochemistryMass spectrometry. Astrobiology 17, 958-961.

Ocean worlds is the label given to objects in the solar system that host stable, globe-girdling bodies of liquid water-oceans. Of these the Earth is the only one to support its oceans on the surface, making it a model for habitable planets around other stars but not for habitable worlds elsewhere in the solar system. Elsewhere in the solar system, three objects Jupiter's moon Europa, and Saturn's moons Enceladus and Titan have subsurface oceans whose existence has been detected or inferred by two independent spacecraft techniques. A host of other bodies in the outer solar system are inferred by a single type of observation or by theoretical modeling to have subsurface oceans. This paper focusses on the three best-documented water oceans beyond Earth: those within Europa, Titan and Enceladus. Of these, Europa's is closest to the surface (less than 10 km and possibly less than 1 km in places), and hence potentially best suited for eventual direct exploration. Enceladus' ocean is deeper 5-40 km below its surface but fractures beneath the south pole of this moon allow ice and gas from the ocean to escape to space where it has been sampled by mass spectrometers aboard the Cassini Saturn Orbiter. Titan's ocean is the deepest perhaps 50-100 km-and no evidence for plumes or ice volcanism exist on the surface. In terms of the search for evidence of life within these oceans, the plume of ice and gas emanating from Enceladus makes this the moon of choice for a fast-track program to search for life. if plumes exist on Europa yet to be confirmed or places can be located where ocean water is extruded onto the surface, then the search for life on this lunar-sized body can also be accomplished quickly by the standards of outer solar system exploration.

Nanometer scale planar Schottky barrier diodes (SBDs) with realistic geometries have been studied by means of a 2-D ensemble Monte Carlo simulator. The topology of the devices studied in this paper is based in real planar GaAs SBDs used in terahertz applications, such as passive frequency mixing and multiplication, in which accurate models for the diode capacitance are required. The intrinsic capacitance of such small devices, which due to edge effects strongly deviates from the ideal value, has been calculated. In good agreement with the classical models, we have found that the edge capacitance is independent of the properties of the semiconductor beneath the contact and, as novel result, that the presence of surface charges at the semiconductor dielectric interface can reduce it almost 15%. We have finally provided a compact model for the total capacitance of diodes with arbitrary shape that could be easily implemented in design automation software such as Advance Design System (ADS).