Journals
2026 EN
Landi AnnaIrene · Carli Cristian · Maturilli Alessandro
+4 more
Abstract Boninites are high‐magnesium volcanic rocks proposed as terrestrial analogs for Mercury's surface, based on elemental data from NASA's MErcury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) mission. In this study, we investigated boninite samples from the Troodos Massif (Cyprus) using a multi‐methodological approach to characterize their mineralogical, chemical, and spectroscopic properties, including reflectance and emissivity spectra. Geochemical analyses confirm that the bulk composition of the samples closely matches Mercury's geochemical terrains in terms of SiO 2 , MgO, and Al 2 O 3 content, though FeO concentrations are higher (∼8 wt% vs. 1–2 wt%). Samples from different localities show some mineralogical differences but generally contain less orthopyroxene and albitic plagioclase than expected on Mercury, along with hydrated minerals from aqueous alteration, which are not expected on the planet's surface. Reflectance spectra in the ultraviolet (UV), visible (VIS), and near‐infrared (NIR) range show major absorption features around 1 μm, associated with mafic minerals, and minor bands at ∼1.4 μm, ∼1.9 μm, and 2.2–2.3 μm, linked to hydrated phases, with spectral variations reflecting mineralogical differences. In the mid‐infrared (MIR) range and emissivity spectra, we observe Christiansen Features (CF) and Reststrahlen Bands (RB) at different positions, mainly influenced by plagioclase content, and shifts in emissivity minima with increasing temperature. Spectral differences between the boninites and Mercury mainly result from the intrinsic mineralogy of the samples. Nonetheless, Troodos boninites represent one of the best Mercury analogs currently available on Earth, and understanding their spectral behavior in relation to their mineralogy could support future investigations with the ESA/JAXA BepiColombo mission.
Journals
2026 EN
Olsen K. S.
Abstract Atmospheric hydrogen chloride (HCl, or hydrochloric acid) has strong links to volcanic activity on Earth. If it is present in the atmosphere of Mars, it could hint at active magmatic processes, or the outgassing from the remnants of recently dormant volcanoes. It has been sought in the Martian atmosphere using terrestrial telescopes and was a target for the ExoMars Trace Gas Orbiter (TGO) mission. Since it was found by TGO, the terrestrial telescopes have returned to their hunt, and the recent study by Faggi et al. (2025), https://doi.org/10.1029/2025je009105 presents the results of a multi‐year campaign to study the global distribution of HCl across the Martian surface. In this commentary, we will examine the importance of HCl, its context in the broader chloride cycle on Mars, how we have gotten to this point, and the implications the new study has on our understanding of its origins.
Journals
2026 EN
Meusburger J. M. · Bristow T. F. · Vaniman D. T.
+6 more
Abstract X‐ray amorphous sulfate hydrates are a substantial component (up to 23 wt%) of the sedimentary rocks and sands analyzed to date by the Mars Science Laboratory Curiosity rover at Gale crater. Recently, the CheMin X‐ray diffractometer observed the amorphization of the crystalline sulfate starkeyite (MgSO 4 · 4H 2 O) upon exposure to the dry and relatively warm atmosphere inside the rover body. To assess the extent to which interactions between minerals and the rover environment contribute to the amorphous component, we investigated the stability of several hydrated minerals under Curiosity‐like conditions. Our results show that highly hydrated minerals are more prone to transformation inside the rover than lower hydrates. Minerals that readily become amorphous under rover conditions are also likely to be unstable when exposed to the dry Martian atmosphere during the warm periods at noon. We therefore suggest that much of the observed amorphization occurred at the Martian surface prior to sampling. Future missions such as the Rosalind Franklin rover and Mars Life Explorer propose to drill into the substantially colder subsurface at Martian mid‐latitudes and are likely to encounter temperature and humidity‐sensitive cryohydrates. To evaluate the original mineral assemblage of rocks on such missions, it will be critical to maintain controlled temperature and relative humidity (RH) conditions inside the rover body. We find that increasing ambient humidity may induce the recrystallization of amorphous salt hydrates, thus controlling RH and temperature inside the rover would significantly enhance the analytical capabilities of a next generation X‐ray diffractometer on Mars.
Journals
2026 EN
Füllekrug Martin · Kosch Michael · Dingley Gavin
+2 more
Abstract Low frequency electromagnetic waves emitted by sprite‐producing lightning are normally measured using vertical electric fields or horizontal magnetic fields. Here we report for the first time the simultaneous measurement of electromagnetic waves from sprite‐producing lightning in all six electromagnetic field componentsE x ,E y ,E z ,H x ,H y , andH z${E}_{x},\ {E}_{y},\ {E}_{z},\ {H}_{x},\ {H}_{y},\ \text{and}\ {H}_{z}$ . A rigorous assessment of the horizontal electric field measurements with dipole antennas in two independent calibration experiments shows that a timing uncertainty of∼ 1 − 2 ${\sim} 1-2$ ns can be achieved, well above the current fundamental limit of the timing accuracy∼ ${\sim} $ 1–5 ps. The coupling between the electric and magnetic fields is quantified using a transfer matrix, allowing the magnetic field to be reconstructed accurately from electric field measurements. The cross product of electric and magnetic fields is used to calculate peak energy fluxes and arrival azimuths from sprite‐producing lightning. It is found that peak energy fluxes vary between∼ ${\sim} $ 10–1,000 μ ${\upmu }$W / m 2$/2}$ and that the differences between the measured and expected arrival azimuths are practically normally distributed with a mean and standard deviation of− 8.0 ° ± 2 . 2 ° ${-}8.0 circ}\pm 2.2 circ}$ . It is concluded that horizontal electric field measurements are well suited to characterize electromagnetic waves with added benefits, including the ease of deployment in harsh environments, cost‐effectiveness and scalability, for example for polarisation measurements in large low frequency arrays. The significance of this study is that it can be used as a pathfinder mission to identify critical technical requirements for the array deployment during the Africa2Moon lander mission.
Journals
2026 EN
Mestici S. · De Michelis P. · Consolini G.
+4 more
Abstract Ionospheric irregularities arise from highly dynamic and turbulent processes related to magnetosphere‐ionosphere coupling and can lead to electromagnetic signal distortion or loss of lock events in global navigation satellite system signals, representing a hazard associated with space weather events. For this reason, understanding and modeling these irregularities and their turbulent nature have become increasingly important. In this study, we present a novel dynamic model that characterizes meso‐scale topside ionospheric irregularity and turbulence indices for different magnetic latitudes, magnetic local times, seasons, solar activity and interplanetary magnetic field orientations (IMF) at high latitudes of both hemispheres. To this aim, we used electron density data at 1 Hz cadence acquired by the Swarm mission in the topside ionosphere and covering 10 years of observations. Our model, based on spherical harmonic decomposition, provides statistical maps of (a) electron density, (b) Rate Of change of electron Density Index (RODI), and (c) a proxy for ionospheric turbulent processes, for fixed solar activity level, local season and IMF orientation as specified by the user. The validation tests demonstrate the model's capability in reproducing the features observed at Swarm altitudes for the analyzed parameters. These promising results pave the way for future applications aimed at forecasting possible space weather hazards associated with the development of turbulent ionospheric irregularities.
Journals
2026 EN
Chamberlin P. C. · DiBraccio G. A. · Borelli R. J.
+7 more
Abstract Space weather monitoring is critical to protect not only our technological assets in space, but also mitigate disruptions to life and society that depends on these vulnerable assets. Significant attention and resources have been dedicated to space weather monitoring at Earth, but little attention to date has been paid to planetary space weather monitoring. The MAVEN mission has instruments and capabilities to monitor solar eruptive events and in situ transients at Mars, but these data are typically not actionable due to long data latencies. Recent efforts have been made to upgrade the data pipeline to produce and serve solar X‐ray and EUV irradiance data from the MAVEN Extreme UltraViolet Monitor (EUVM) instrument with low‐latency, and these data are now available. This paper describes this MAVEN EUVM data real‐time processing and the space weather data products that are now available near real‐time to monitor space weather from Mars.
Journals
2026 EN
Zhang Chao · Liu Weihao · Guo Jingnan
+2 more
Abstract Crewed missions to Mars will be a milestone of future space exploration programs. However, the absence of Earth's magnetic field leaves astronauts directly exposed to unattenuated energetic particles in deep space, primarily galactic cosmic rays (GCRs), resulting in significantly higher radiation levels and enhanced health risks. Understanding and quantifying these radiation hazards is thus essential for evaluating the feasibility and safety of long‐duration Mars missions. Based on the dose data from the Trace Gas Orbiter mission and the Cosmic Ray Telescope for the Effects of Radiation (CRaTER), we perform correlation analyses between the measured dose rate and solar modulation conditions, parameterized as solar modulation potential, and develop empirical models that can be extrapolated to a broader range of solar activities. Using these models, the GCR‐cumulative dose for mission scenarios following three different transfer trajectories under varying solar modulation conditions during the past ∼60 years are calculated. Our results indicate that missions operated during solar maximum accumulate 30%–55% less GCR effective dose than those during solar minimum, with the specific percentage depending on their execution period and trajectory. Under similar shielding conditions of measurements used here, missions following the minimum energy trajectory and conducted during relatively active solar cycles can generally maintain the cumulative radiation effective dose below 1,000 mSv, but keeping it below the NASA's new limit of 600 mSv requires restricting the mission duration to the solar maximum. Nevertheless, faster transfer orbits can help satisfy this limit during solar minimum years.
Journals
2026 EN
Chou MinYang · Hozumi Yuta · Yue Jia
+3 more
Abstract This study investigates the linkage between mesopause gravity waves and equatorial plasma bubbles (EPBs) from 2012 to 2015 using the collocated nightglow measurements, O 2 (762 nm) and OI (630 nm), observed by the Visible and near‐Infrared Spectral Imager onboard the International Space Station under the Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere (ISS‐IMAP/VISI) mission, along with the ionospheric observations from FORMOSAT‐3/COSMIC (F3/C). ISS‐IMAP/VISI observed a persistent three‐peak longitudinal structure of gravity wave activity near the magnetic equator in South American, African, and South Asian sectors across all seasons. The gravity waves also exhibit significant seasonal latitudinal variations, consistent with the seasonal migration of the Inter‐Tropical Convergence Zone (ITCZ). Notably, the longitudinal distribution of gravity wave occurrences aligns well with the longitudinal pattern of EPB occurrence observed by both VISI and F3/C, particularly over the South American‐African sectors, establishing that ITCZ‐driven gravity waves are the potential seeding source for EPBs. Analysis of ionospheric background conditions relevant to Rayleigh‐Taylor instability confirms that while these conditions strongly influence the seasonal‐longitudinal distribution of EPBs, the presence of gravity waves acts as the modulator of EPB occurrence. Overall, the VISI EPB occurrence rates are consistent with the product of VISI gravity wave and favorable background condition probabilities, demonstrating that the climatology of EPBs is synergistically governed by the gravity wave seeding and ionospheric conditions.
Journals
2026 EN
Soylu M. E. · Entekhabi D. · Bras R. L.
Abstract Knowledge of the groundwater recharge rate determines whether aquifer use is sustainable. However, accurately measuring recharge globally presents significant challenges due to the complexity of subsurface processes and the lack of direct observational methods. This study addresses these challenges by developing a methodology that integrates satellite data, numerical models, and machine learning to estimate groundwater recharge globally. The methodology involves two steps. First, we run a numerical model, Hydrus‐1D, to simulate soil moisture fluxes in the unsaturated zone by solving the Richards equation in the vertical direction for 235 different points representing various climates and soil types across the globe. Second, using Hydrus‐1D inputs and outputs, we train a supervised ensemble machine‐learning model, specifically a Gaussian Process Regression model, as an emulator to mimic Hydrus‐1D. This enables us to process satellite observations efficiently to estimate annual recharge flux globally. Inputs for the model include NASA's SMAP soil moisture and GPM precipitation observations, ERA5 climate reanalysis data, and soil hydraulic properties. Rainfall, unsaturated hydraulic conductivity, and soil moisture are identified as the most significant predictors of groundwater recharge. The approach effectively captures global recharge patterns, particularly in regions with high rainfall, though it shows some limitations in arid areas with minimal recharge and heavily irrigated areas. We confirm the reasonableness of recharge estimates by comparing them with observed changes in subsurface water storage from the GRACE satellite mission. The method effectively captures the observed trends in water storage, demonstrating the model's capability to estimate recharge using large‐scale satellite and reanalysis data.
Journals
2026 EN
Ma Xiaoyu · Wang Jida · Gharari Shervan
+2 more
Abstract Reservoirs play a critical role in water management, yet comprehensive and real‐time observations of reservoir storage remain limited, especially outside the U.S. Observations of two reservoir‐related attributes, Water Surface Elevation (WSE) and Surface Area (SA), which can be used to calculate reservoir storage change, are often desynchronized, hindering precise estimation. The recently launched (December 2022) Surface Water and Ocean Topography (SWOT) satellite mission (science observations began August 2023) uses a cutting‐edge interferometer to provide global, simultaneous WSE and SA maps of Earth's water bodies, which can be leveraged to estimate reservoir storage. We evaluate the accuracy of SWOT‐based estimates of reservoir storage in comparison with in situ‐based observations for 12 reservoirs in the Western U.S., of which four are in California, four are in the Upper Colorado River Basin (UCRB), and four are in the Columbia River Basin (CRB). Our results show that SWOT produces WSE measurements with less than 20 cm median absolute error (MAE) taken across all 12 reservoirs and 19 months of observations and storage estimates with MAE less than 10%. Model‐based reservoir storage estimates (constrained by SWOT observations) can fill temporal gaps accurately and efficiently, even if fewer than one‐quarter of SWOT observations are valid. Our results motivate further study of the potential for estimation of reservoir storage where few or no in situ observations are available via assimilation of SWOT observations into a reservoir simulation model.