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Magnetic fields around Mars shape the pathways of energy input into, and ion escape from, the Martian atmosphere, thereby potentially affecting the atmospheric evolution of Mars. The Martian magnetic field environment is primarily determined by the global electric current system resulting from the solar wind interaction with the upper atmosphere and crustal magnetic fields of Mars. Recently, it has been recognized that neutral wind-driven ionospheric dynamo currents generate magnetic field perturbations observable in orbits and on the surface of Mars. However, the entire system of near-Mars currents is not fully understood. Here we present a newly identified current system in the Martian magnetosphere directly coupled to the wind-driven ionospheric currents, based on the spherical harmonic analysis of magnetic field data obtained by the Mars Atmosphere and Volatile Evolution spacecraft. This magnetospheric current system can be explained by diamagnetic currents associated with magnetic fields generated by the wind-driven ionospheric dynamo currents. Our results demonstrate a close coupling between the neutral atmospheric dynamics and the high-altitude magnetospheric current system at Mars mediated by wind-driven ionospheric dynamo currents. This reveals a previously unrecognized role of the neutral atmosphere in controlling magnetic field environments of unmagnetized planets.

The MAVEN Solar Energetic Particle (SEP) instrument is designed to measure the energetic charged particle input to the Martian atmosphere. SEP consists of two sensors mounted on corners of the spacecraft deck, each utilizing a dual, double-ended solid-state detector telescope architecture to separately measure fluxes of electrons from 20 to 1000 keV and ions from 20–6000 keV, in four orthogonal look directions, each with a field of view of 42 ∘ by 31 ∘ . SEP, along with the rest of the MAVEN instrument suite, allows the effects of high energy solar particle events on Mars’ upper atmospheric structure, temperatures, dynamics and atmospheric escape rates, to be quantified and understood. Given that solar activity was likely substantially higher in the early solar system, understanding the relationship between energetic particle input and atmospheric loss today will enable more confident estimates of total atmospheric loss over Mars’ history.

Since 2021, a new surge in discrete aurora detections at Mars has been observed by the Emirates Mars Ultraviolet Spectrometer (EMUS) onboard the Emirates Mars Mission (EMM) Hope Orbiter as EMUS started to regularly obtain synoptic auroral images with a high sensitivity. Here we report on a fortuitous conjunction between EMM and Mars Express (MEX) using far ultraviolet (FUV) imaging of discrete aurora by EMM EMUS, in situ measurements of suprathermal electrons by the MEX Analyzer of Space Plasma and Energetic Atoms Electron Spectrometer (ELS), and topside radar sounding of the nightside ionosphere by the MEX Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS). In this event, EMM EMUS imaged a clear discrete aurora signature around moderately strong crustal magnetic fields on the nightside near the dusk terminator, 11 min before which MEX MARSIS measured a prominent local enhancement of the peak electron density in the nightside ionosphere and MEX ELS observed an in situ enhancement of suprathermal electrons at the corresponding location. A remarkable geographic agreement is found between the enhancements of the aurora, ionosphere, and suprathermal electrons, suggesting that the enhanced ionization and auroral emission are caused concurrently by precipitating suprathermal electrons. Subsequent images indicate that the discrete aurora slightly changed its shape in 15 min and mostly disappeared in a few hours. The MEX MARSIS measurements of the auroral ionosphere display overlapping ionospheric and surface echoes indicative of horizontal gradients of the peak electron density. Analysis of the overlapping echoes implies that the auroral ionosphere and electron precipitation could be highly structured with horizontal spatial scales on the order of several tens of km. MEX MARSIS also observed a non-auroral ionospheric enhancement with a wider spatial extent than the local auroral enhancement, suggesting alternative sources of the enhanced nightside ionosphere such as plasma transport. The comparison between the ionospheric structures measured by MEX MARSIS, suprathermal electron flux measured by MEX ELS, and discrete auroral emission imaged by EMM EMUS underscores the complexity of the auroral and non-auroral nightside ionospheres. This motivates further investigations of their sources, transport, and connections to the magnetotail dynamics of Mars. Graphical Abstract

The nightside ionosphere of Mars is known to be highly variable: electron densities are below detection thresholds in certain regions and are almost comparable to the photoionization‐produced dayside ionosphere in others. The factors controlling its structure include thermospheric densities, temperatures and winds, day‐night plasma transport, plasma temperatures, current systems, meteoroid ablation, solar and galactic energetic particle events, and magnetic field geometry‐topology and electron precipitation, none of which are adequately understood at present. Using a kinetic approach called Mars Monte Carlo Electron Transport, we model the dynamics of precipitating electrons on the nightside of Mars to study the impact of these last two listed factors (magnetic fields and electron precipitation) on ionospheric structure. As input, we use precipitating electron energy spectra and pitch angle distributions from the Mars Global Surveyor Magnetometer and Electron Reflectometer. We thus calculate ionization rate in three dimensions, both for specific observations and average cases. The very highest average rates are equivalent to photoionization rates on the dayside at high solar zenith angle. We predict complex geometrical patterns in the ionization and huge variability (∼4 orders of magnitude) in peak ionization rates, both on single orbits and between the averages for different geographic regions, and find a bimodal distribution of predicted ionization rates where the highest rates correlate with the most vertical magnetic fields. This model can be used as input to electrodynamic models of the Mars ionosphere, which can be compared with, and informed by, data from the upcoming 2013 Mars Atmosphere and Volatile Evolution Mission. Key Points Nightside ionization depends on crustal magnetic field topology Peak ionization rates vary by approximately 4 orders of magnitude Highest ionization rates correlate with the most vertical magnetic fields

Remote sensing technologies are experiencing a surge in adoption for monitoring Earth’s environment, demanding more efficient and scalable methods for image analysis. This paper presents a new approach for the Emirates Mars Mission (Hope probe); A serverless computing architecture designed to analyze images of Martian auroras, a key aspect in understanding the Martian atmosphere. Harnessing the power of OpenCV and machine learning algorithms, our architecture offers image classification, object detection, and segmentation in a swift and cost-effective manner. Leveraging the scalability and elasticity of cloud computing, this innovative system is capable of managing high volumes of image data, adapting to fluctuating workloads. This technology, applied to the study of Martian auroras within the HOPE Mission, not only solves a complex problem but also paves the way for future applications in the broad field of remote sensing.

Bow shock, where the solar wind first encounters the Martian environment, reflects the complex interplay between the solar wind and Martian upper atmosphere and crustal fields. However, a comprehensive understanding of Martian bow shock dynamics remains elusive due to limited multi-spacecraft observations. Here, leveraging the joint observations from China’s Tianwen-1 and NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN), we reveal Martian bow shock oscillations with a temporal scale of minutes and spatial extents of hundreds of kilometers during weakly disturbed solar wind. Our analysis of the observations along with three-dimensional simulations suggests that magnetosonic Mach number is the most sensitive parameter influencing the bow shock, and a slow solar wind stream that favors low Mach numbers may lead to the large-scale bow shock oscillations and the whole Martian space environment. This finding advances our understanding of the interactions between the solar wind and non-magnetized planets. Mars’ bow shock, where the solar wind meets the planet’s plasma environment, responds dynamically to solar wind conditions. Here, the authors show that even under relatively calm solar wind, it globally oscillates within minutes and shifts by hundreds of kilometers.

This study investigates the escape of Mercury's sodium‐group ions (Na+‐group, including ions with m/q from 21 to 30 amu/e) and their dependence on true anomaly angle (TAA), that is, Mercury's orbital phase around the Sun, using measurements from MESSENGER. The measurements are categorized into solar wind, magnetosheath, and magnetosphere, and further divided into four TAA intervals. Na+‐group ions form escape plumes in the solar wind and magnetosheath, with higher fluxes along the solar wind's motional electric field. The total escape rates vary from 0.2 to 1 × 1025 atoms/s with the magnetosheath being the main escaping region. These rates exhibit a TAA dependence, peaking near the perihelion and similar during Mercury's remaining orbit. Despite Mercury's tenuous exosphere, Na+‐group ions escape rate is comparable to other inner planets. This can be attributed to several processes, including that Na+‐group ions may include several ion species, efficient photoionization frequency for elements within Na‐group, etc. Plain Language Summary Atmospheric escape is defined as the loss of atmospheric particles in the form of neutrals and ions into outer space. Understanding atmospheric escape is a fundamental science question for studying the evolution of planetary atmosphere and habitability, as it can provide insight into how life can form on a planet. While atmospheric escape has been extensively studied in Venus, Earth, and Mars through in situ measurements and simulations, it remains poorly understood at Mercury. In this study, we investigate the escape of the most abundant heavy ions at Mercury, specifically the Na+‐group ions, using MESSENGER's measurements. Our findings show that the escape rates of the Na+‐group ions are dependent on Mercury's orbital phase around the Sun, exhibiting a seasonal effect with rates from 0.2 to 1 × 1025 atoms/s. This rate is comparable to the ion's escape rates at other inner planets, which is surprising given that Mercury only has a tenuous exosphere. We propose that this can be attributed to several processes such as efficient photoionization, solar wind sputtering, and solar wind momentum exchange at Mercury, and the Na+‐group ions include several ion species such as Na+, aluminum ion (Al+), silicon ion (Si+) and magnesium ion (Mg+) etc. Key Points Na+‐group ions form escape plumes in solar wind and magnetosheath, with higher fluxes in the positive solar wind electric field hemisphere The escape rate ranges from 0.2 to 1 × 1025 atoms/s, with the magnetosheath being the main escaping region Escape rates peak near perihelion, and are similar during other true anomaly angle (TAA) intervals

The Emirates Mars Mission (EMM) – Hope Probe – was developed to understand Mars atmospheric circulation, dynamics, and processes through characterization of the Mars atmosphere layers and its interconnections enabled by a unique high-altitude (19,970 km periapse and 42,650 km apoapse) low inclination orbit that will offer an unprecedented local and seasonal time coverage over most of the planet. EMM has three scientific objectives to (A) characterize the state of the Martian lower atmosphere on global scales and its geographic, diurnal and seasonal variability, (B) correlate rates of thermal and photochemical atmospheric escape with conditions in the collisional Martian atmosphere, and (C) characterize the spatial structure and variability of key constituents in the Martian exosphere. The EMM data products include a variety of spectral and imaging data from three scientific instruments measuring Mars at visible, ultraviolet, and infrared wavelengths and contemporaneously and globally sampled on both diurnal and seasonal timescale. Here, we describe our strategies for addressing each objective with these data in addition to the complementary science data, tools, and physical models that will facilitate our understanding. The results will also fill a unique role by providing diagnostics of the physical processes driving atmospheric structure and dynamics, the connections between the lower and upper atmospheres, and the influences of these on atmospheric escape.

Based on decades of single-spacecraft measurements near 1 au as well as data from heliospheric and planetary missions, multi-spacecraft simultaneous measurements in the inner heliosphere on separations of 0.05–0.2 au are required to close existing gaps in our knowledge of solar wind structures, transients, and energetic particles, especially coronal mass ejections (CMEs), stream interaction regions (SIRs), high speed solar wind streams (HSS), and energetic storm particle (ESP) events. The Mission to Investigate Interplanetary Structures and Transients (MIIST) is a concept for a small multi-spacecraft mission to explore the near-Earth heliosphere on these critical scales. It is designed to advance two goals: (a) to determine the spatiotemporal variations and the variability of solar wind structures, transients, and energetic particle fluxes in near-Earth interplanetary (IP) space, and (b) to advance our fundamental knowledge necessary to improve space weather forecasting from in situ data. We present the scientific rationale for this proposed mission, the science requirements, payload, implementation, and concept of mission operation that address a key gap in our knowledge of IP structures and transients within the cost, launch, and schedule limitations of the NASA Heliophysics Small Explorers program.

The night side ionosphere of Mars is known to be highly variable: essentially nonexistent in certain geographic locations, while occasionally nearly as strong as the photoionization‐produced dayside ionosphere in others. The factors controlling its structure include thermospheric densities, temperatures and winds, day‐night plasma transport, plasma temperatures, current systems, solar particle events, crustal magnetic fields, and electron precipitation, none of which are adequately understood at present. Using a kinetic Monte Carlo approach called Mars Monte Carlo Electron Transport (MarMCET), we model the dynamics of precipitating solar wind electrons on the nightside ionosphere of Mars to study the effects of these last two factors on ionospheric density and structure. We calculate ionization rate profiles and, using simple assumptions concerning atmospheric chemistry, also calculate electron density profiles, total electron content, and equivalent ionosphere slab thickness. We present the first model investigation of the coupled effects of crustal magnetic field gradients and precipitating electron pitch angle distributions (PADs). Including such effects, particularly in cases of nonisotropic PADs, is found to be essential in accurately predicting ionization rate and electron density profiles: peak ionization rates can vary by a factor of 20 or more when these effects are included.