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The state-to-state (STS) inelastic energy transfer and O-atom exchange reaction between O and CO(v), as two fundamental processes in non-equilibrium air flow around spacecraft entering Mars' atmosphere, yield the same products and both make significant contributions to the O + CO(v) → O + CO(v′) collisions. The inelastic energy transfer competes with the O-atom exchange reaction. The detailed reaction mechanisms of these two elementary processes and their specific contributions to the CO relaxation process are still unclear. To address these concerns, we performed systematic investigations on the 3A′ and 3A″ potential energy surfaces (PESs) of CO2 using quasi-classical trajectory (QCT) calculations. Analysis of the collision mechanisms reveals that inelastic collisions have an apparent PES preference (i.e., they tend to occur on the 3A′ PES), while reactive collisions do not. Reactive rates decrease significantly when the total collision energy approaches dissociation energy, which differs from the inelastic process. Inelastic rates are generally lower than the reactive rates below ∼10 000 K, except for single quantum jumps, whereas the reverse is observed above ∼10 000 K. In addition, by combining QCT with convolutional neural networks, we have established neural network (NN)-STS1 (inelastic) and NN-STS2 (reactive) models to generate all possible STS cross sections. The NN-based models accurately reproduce the results calculated from QCT calculations. In this study, all calculations have been focused on analyzing collisions at the ground rotational level. [ABSTRACT FROM AUTHOR]

ABSTRACT This study explores nitrogen fixation in the Martian atmosphere using plasma technology. By combining microwave and dielectric barrier discharges (DBD), nitrogen was converted into water‐soluble nitrogen fertilizer (N₂O₅) for agriculture. Despite the low pressure and temperature of Mars, optimized discharge conditions and reactor design significantly boosted the generation efficiency of N₂O₅ precursors, NO₂, and O₃ production. The microwave discharge achieved NOx concentrations of 63.6 ppm, close to experimental values; adjusting DBD pressure to 760 Torr enhanced O₃ concentration by 105 times, yielding 3.8 mol/m³ N₂O₅. The findings lay a technological foundation for future Martian ecosystem development and highlight the need for further experimental validation and system optimization. [ABSTRACT FROM AUTHOR]

The Martian magnetotail is largely controlled by the solar wind (SW) and is modulated by variations in the upstream drivers. However, due to the limitations of single‐spacecraft observations, the effects of SW variations on the Martian magnetotail have not been fully understood so far. Here, using Tianwen‐1 and MAVEN data, we report for the first time the rapid response of Martian magnetotail to the SW disturbance. In our study, Tianwen‐1 detected the flapping of Martian magnetotail, while MAVEN monitored disturbances in the upstream SW. The results indicate that a 20% increase (or decrease) in SW dynamic pressure and a 30° (or 50°) rotation of interplanetary magnetic field clock angle could cause the Martian magnetotail to swing rapidly. These two SW disturbances could lead to oscillations of the Martian magnetotail. This study reveals the importance of joint observations for studying the interaction between the SW and Mars. Plain Language Summary: Mars lacks an intrinsic global magnetic field and as a result solar wind (SW) interacts directly with its ionosphere and atmosphere, leading to a high dependence of the Martian induced magnetosphere on SW conditions. Understanding the interaction between the SW and Mars can provide critical information for studies of planetary evolution, especially the effect of the SW on the Martian magnetotail. In previous studies, using single satellite observations, we limit ourselves to studying some local physical processes or statistical properties. Here, based on the joint measurements by Tianwen‐1 and MAVEN, we observed the rapid response of Martian magnetotail to the SW disturbance, finding that a 20% increase (or decrease) in SW dynamic pressure and a 30° (or 50°) rotation of IMF clock angle could cause the Martian magnetotail to swing rapidly. These two SW disturbances could lead to oscillations of the Martian magnetotail. These results can help us understand the SW interaction with the Martian induced magnetosphere. Key Points: We report for the first time the rapid response of Martian magnetotail to the solar wind (SW) disturbance by using Tianwen‐1 and MAVEN dataA 20% increase (or decrease) in PSW and a 30° (or 50°) rotation of interplanetary magnetic field clock angle could cause the Martian magnetotail to swingThese two SW disturbances could lead to oscillations of the Martian magnetotail [ABSTRACT FROM AUTHOR]

Mars' dayside ionosphere is maintained primarily by ionization from solar ultraviolet photons and subsequent chemical reactions, with small contributions from other mechanisms such as impact ionization and charge exchange. In December 2023, the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission observed the impact of an interplanetary coronal mass ejection (ICME) on Mars' ionosphere, including strongly enhanced fluxes of suprathermal electrons. We show that this enhancement in suprathermal electron fluxes increased ion production from electron impact, so that dayside electron impact ionization rates exceeded photoionization rates during the ICME. This change in ion production mechanisms led to unusually high densities of the minor ions C+ ${\mathrm{C}}^{+}$ and O++ ${\mathrm{O}}^{++}$. Space weather events are known to increase ion escape rates, so changes in ion composition during space weather events have important implications for atmospheric evolution. We show that scaling nominal loss rates to account for space weather may underestimate carbon loss from Mars' atmosphere. Plain Language Summary: Dayside planetary ionospheres are primarily produced through interactions between atmospheric neutral gases and sunlight. Impact by energetic particles, especially electrons, typically only contributes a small amount of plasma. We observed unusually high densities of the minor ions C+ ${\mathrm{C}}^{+}$ and O++ ${\mathrm{O}}^{++}$ in Mars' ionosphere during a space weather event in December 2023, when a large bubble of magnetized plasma launched from the Sun impacted the planet. This plasma bubble compressed the Mars magnetosheath, pushing suprathermal electrons to lower altitudes, where they impacted the atmosphere and significantly increased plasma production through impact ionization. Changes in the production mechanisms of the ionosphere during space weather events lead to changes in its density and composition. This is important because space weather events are known to increase the amount of atmospheric gas escaping from a planet, which can have important implications for how the atmosphere evolves over millions of years. Key Points: Unexpected increases in C+ and rarely detected O++ densities were observed during the December 2023 space weather event at MarsThese ions were produced by electron impact ionization from the intense electron fluxes associated with the space weather eventElectron impact ionization exceeded photoionization during the event, which temporarily altered the composition of ions escaping Mars [ABSTRACT FROM AUTHOR]

Water and carbon dioxide each form mesospheric clouds on Mars. At such altitudes (40–100 km), clouds may remain sunlit for part of the night. We describe a previously unreported, visually spectacular season of iridescent, noctilucent clouds visible in early southern autumn from the Curiosity rover's site in Gale crater. Ice nucleation begins near sunset with a narrow range of particle sizes, and the ice aerosols grow and precipitate. The iridescence, visible through three‐color imaging, arises from locally uniform particle sizes resulting from similar growth histories. Colorful fall streaks show the clouds evolving, and a scattering corona shows size uniformity over large areas. The terminator was observed on the clouds, allowing the determination of cloud altitudes and a likely CO2 composition. This is the first observation of particle size variations within individual Martian clouds, allowing a new probe of Martian cloud physics. Plain Language Summary: Water and carbon dioxide each form high‐altitude (40–100 km) clouds on Mars. Clouds at those altitudes on Earth can be noctilucent—night‐shining—when they are illuminated by sunlight while the world below is dark. Noctilucent clouds have been seen on Mars but were not expected around the Curiosity rover site. Curiosity rover images from early southern autumn show clouds that are not only noctilucent, but they are also colorful with a mother‐of‐pearl appearance due to iridescence—such clouds are called nacreous on Earth. Curiosity's environmental data record shows that the clouds have consistently formed near sunset in that season. By looking at the timing of when Mars' shadow falls on the cirrus‐like clouds, we found that they are 50–80 km high and are probably carbon dioxide ice, but there are lower layers of wave‐like clouds that may be water ice. The pastel red, orange, green, and blue fringes of the clouds, which would be easily visible to an astronaut on Mars, help us understand the size of the cloud particles and how they grow and change. Key Points: Curiosity rover images reveal a previously unknown, visually spectacular cloud season in the Martian tropics during early southern autumnIridescence in the noctilucent clouds requires a narrow particle size distribution, implying a brief evolution in a uniform environmentSuch images, with contextual information, probe the formation and growth processes within Martian clouds [ABSTRACT FROM AUTHOR]

The article "The entrainment hypothesis – 80 years old and still going strong" published in the Journal of Fluid Mechanics discusses the entrainment hypothesis proposed by G. I. Taylor 80 years ago. The hypothesis states that the mean inflow velocity across the boundary of a turbulent flow is proportional to a characteristic velocity of the flow. The article explores the application of this hypothesis in various geophysical flows, such as convective clouds, ocean currents, and magma chambers, highlighting its success in predicting entrainment. Additionally, the article delves into the impact of the entrainment hypothesis on disciplines like engineering and oceanography, emphasizing its significance in understanding turbulence and mixing in stratified fluids. [Extracted from the article]

Due to the Mars rotorcraft can conduct extensive surface exploration of Mars and carry sampler for collecting samples on the Martian surface, it is gradually becoming the mainstream exploration devices for Mars missions. In response to the thin atmosphere on Mars, with the flight duration and sample-carrying capacity of the quadcopter as constraints, we design the propulsion system parameters for the Mars quadcopter with the function of sampling on the Martian surface. A method for evaluating rotor performance indicators, including mass and Mach number at the tip of the blade, is proposed. Based on the evaluation index and the steady RANS method for predicting the lift and drag characteristics of the rotor, an appropriate rotor diameter for the Mars quadrotor is selected. The method combining NSGA-II and two-dimensional steady RANS is employed to optimize the airfoil of the Mars quadcopter blade under the condition of a chord length of 40 mm, a Mach number of 0.43, an angle of attack of 20°, and a Reynolds number based on chord of 6080. Experimental verification for the lift-to-drag characteristics of the single rotor is conducted in an environment simulating the atmospheric density on the Martian surface. The results show that the blade after optimization can generate a thrust of 5.95 N and consume power of 164.9 W, at the rotational speed of 3650 r/min. Based on the test bench with the function of sliding up and down for testing aerodynamic performance of quadcopter, the temperature of the motor and battery discharge characteristics of the Mars quadcopter are conducted. The results of the test show that the quadrotor can provide a thrust-to-weight ratio of 1.66 for the Mars quadcopter while meeting the design requirement of 3 min. • A indicator for evaluating rotor aerodynamic performance is proposed. • The propulsion system for the Mars quadcopter is designed. • The experimental verification is conducted in simulated atmosphere of Mars. • The propulsion system can provide a thrust-to-weight ratio of 1.66 and sustain 180 s. [ABSTRACT FROM AUTHOR]

The Mars NO and the O2 nightglow are produced by the recombination of atoms produced on the dayside by photodissociation and transported to the nightside. These emissions are tracers of the summer to winter pole dynamics in the upper Mars atmosphere. The UV‐visible (UVIS) channel of the Nadir and Occultation for MArs Discovery (NOMAD) spectrometer onboard Trace Gas Orbiter (TGO) is the first instrument able to simultaneously monitor both nightglow emissions. Observations by NOMAD/UVIS during the first part of the Martian year show that both the NO and O2 nightglow emissions are enhanced near the southern winter pole. Their mean brightnesses are 15 and 108 kR, respectively. These nightglow emissions generally occur between 30 and 60 km, the NO emitting layer being consistently located ∼10 km higher than the O2 nightglow layer. Numerical simulations with the Mars Planetary Climate Model (MPCM, v6.1) properly reproduce the nightglow brightness but tend to overestimate the NO peak altitude by ∼10 km. These results suggest that the atomic oxygen density is correctly predicted by the model but that the nitrogen density altitude distribution might not be properly modeled. Plain Language Summary: Nightside emissions of the Martian upper atmosphere are excited by the recombination of atoms created on the dayside. For the first time, the NO ultraviolet emission and the O2 visible emission have been observed simultaneously with the UV‐visible (UVIS) channel of the Nadir and Occultation for MArs Discovery (NOMAD) spectrometer onboard Trace Gas Orbiter (TGO). They are used as tracers of the atmospheric dynamics to demonstrate the summer to winter pole circulation that governs the Mars upper atmosphere. We show that the two nightglow layers occur between 30 and 60 km and that they are separated by ∼10 km. We compare our results with simulations from the Mars Planetary Climate Model. Simulations manage to properly reproduce the nightglow brightness but tend to overestimate the NO peak altitude by ∼10 km. These results suggest that the atomic oxygen density is correctly predicted by the model but that the altitude distribution of the nitrogen density might not be properly modeled. Key Points: For the first time, NOMAD/UVIS simultaneously monitors both the NO UV and O2 visible nightglow in the Mars southern winter atmosphereThe NO emitting layer is consistently located ∼10 km above the O2 nightglow layer (∼55 and ∼45 km, respectively)Brightness is overall well predicted but the altitude difference between the two polar emission layers is overestimated by the MPCM v6.1 model [ABSTRACT FROM AUTHOR]

The polar vortices of Mars are characterized by strong zonal winds that isolate cold air above the pole, allowing CO2 to condense out of the atmosphere through snowfall and direct deposition. Due to their key role in seasonal variability of the atmosphere, it is important to understand the different factors that affect the strength, shape, and stability of the polar vortices and processes such as snowfall that occur within. We used atmospheric retrievals of temperature and CO2 ice cloud opacity from the Mars Climate Sounder (MCS) on board NASA's Mars Reconnaissance Orbiter (MRO) to characterize and analyze patterns in the polar vortices and CO2 ice clouds for Mars years (MY) 29–36. We couple the MCS data with a one‐dimensional snowfall model to determine CO2 snow precipitation rates and analyze patterns in the amounts and distribution of snowfall. We characterize the elliptical nature of both vortices and find that there is significant shrinking and warming of the polar vortex during regional dust storms in the summer hemisphere, which occur more frequently during northern winter. We also find that snowfall in the north pole exceeds that in the south and accounts for ∼1% of surface CO2 deposition, with a notable pause in snowfall during the solstice. We also find measurable variability in snowfall driven by both regional and global dust storms and persistent yearly patterns in the spatial distribution of snow clouds. Plain Language Summary: During the winter season when no sunlight reaches the pole of Mars, the atmosphere grows cold and strong winds trap a cold pocket of air above the poles. This region, called the polar vortex, reaches temperatures that are cold enough for CO2 ice (dry ice) snow clouds to form and snow out. Understanding this process and its effects will provide important insights into the overall physics of the Martian atmosphere and how it behaves over time. In this work, we use data from the Mars Climate Sounder to characterize the shape and temperature of the winter polar vortex in both poles and analyze changes with time. We find that most dust storms in the opposing hemisphere cause the polar vortex to shrink and warm. We also use the data to calculate the amount of snowfall occurring in the winter seasons and find that there is significant snowfall occurring in the north pole, accounting for ∼1% of seasonal CO2 exchange. We also find that there are notable patterns in the distribution of snowfall over both location and time. Key Points: The shape, size, and stability of the Martian polar vortices are controlled by topography, dust loading, and insolationMore snowfall occurs in the northern winter, with a notable reduction during solstice and following some dust activityThe south‐polar vortex has a more consistent size and shape than the north due to the less frequent dust activity during northern summer [ABSTRACT FROM AUTHOR]

Utilizing Mars Atmosphere and Volatile EvolutioN (MAVEN) observations from October 2014 to May 2023, we perform a detailed survey of magnetosonic waves generated in the solar wind (refer to as upstream MS waves), with frequencies near the proton gyrofrequency in the solar wind environment. The distribution of the solar wind‐generated MS waves has been carefully investigated, including in the solar wind and in the Martian magnetosphere by propagation. The results show that these MS waves are widely distributed below the Martian bow shock but are more concentrated below the magnetic pileup boundary, particularly in the subsolar region. The waves possess higher occurrence rates on the dayside with larger amplitudes; the occurrence rates also show dusk‐side‐preferred asymmetry. The Martian crustal magnetic field can prevent MS waves from penetrating into lower altitudes, while higher solar dynamic pressure benefits their penetration. The wave amplitudes exhibit a weak positive correlation with the solar wind dynamic pressure. These obtained global distribution features of Martian upstream MS waves observed by MAVEN are valuable to improve current understanding of the dynamic variations of Martian charged particles and the underlying contribution of wave‐particle interactions driven by MS waves. Plain Language Summary: Magnetosonic waves with frequencies near the proton gyrofrequency in the solar wind environment play an important role in altering the plasma and atmospheric environment of the planet through interactions with charged particles. In this study, we statistically investigate, using Mars Atmosphere and Volatile EvolutioN observations from October 2014 to May 2023, how these waves, referred to as upstream MS waves, are distributed in the Martian space. They are found to occupy the space downstream of the bow shock but are more concentrated below the magnetic pileup boundary. Also, they are seen more frequently on the dayside and dusk side than on the other halves. The penetration of upstream MS waves becomes difficult when encountering the Martian crustal field, or when the solar dynamic pressure is lower than usual. The amplitude of waves tends to grow larger when the solar dynamic pressure increases. These results can greatly benefit studies on how charged particles can be accelerated by the waves and escape from Mars, which could profoundly change the climate of this planet. Key Points: Upstream MS waves are predominantly below the dayside magnetic pileup boundary of Mars with a dawn‐dusk asymmetry in distributionUpstream MS waves can more easily propagate to lower altitudes in the dayside regions with weak crustal magnetic field of MarsSolar wind dynamic pressure can influence the occurrence of upstream MS waves [ABSTRACT FROM AUTHOR]

Featured Application: To compute total spectral irradiance on the surface of Mars from a selected value of correlated color temperature in the range of 2333 K–5868 K. We analyzed the main colorimetric characteristics of lights on Mars' surface from 3139 total spectral irradiances provided by the COMIMART model (J. Space Weather Space Clim. 5, A33, 2015), modifying the parameters of 'solar zenith angle' and 'opacity', related to the time of day and the amount of dust in the atmosphere of Mars, respectively. Lights on Mars' surface have chromaticities that are mainly located below the Planckian locus, correlated color temperature in the range of 2333 K–5868 K, and CIE 2017 color fidelity indices above 93. For the 24 samples in the X-Rite ColorChecker® and an extreme dust opacity change from 0.1 to 8.1 in the atmosphere, the average color inconstancy generated by the change in Mars' light using the chromatic adaptation transform CIECAT16 was about 5 and 8 CIELAB units for solar zenith angles of 0° and 72°, respectively. We propose a method to compute total spectral irradiances on the surface of Mars from a selected value of correlated color temperature in the range of 2333 K–5868 K. This method is analogous to the one currently adopted by the International Commission on Illumination to compute daylight illuminants on the surface of Earth (CIE 015:2018, clause 4.1.2). The average accuracy of 3139 reconstructed total spectral irradiances using the proposed method was 0.9999558 using GFC (J. Opt. Soc. Am. A 14, 1007–1014, 1997) and 0.0009 ΔEu′v′ units, a value just below noticeable chromaticity differences perceptible by human observers at 50% probability. Total spectral irradiances proposed by Barnes for five correlated temperatures agreed with those obtained from the current proposed method: on the average, GFC = 0.9979521 and 0.0023 ΔE′v′ units. [ABSTRACT FROM AUTHOR]

To investigate the excitation mechanism of ionospheric perturbations on Mars by the Neutral Gas and Ion Mass Spectrometer (NGIMS) onboard Mars Atmosphere and Volatile EvolutioN (MAVEN), we categorize ionospheric perturbations into three cases: (a) the ion‐neutral coupling cases where ion and neutral perturbations are well coupled, (b) the ion‐specific cases where ion perturbations move independently from neutrals, and (c) the coronal mass ejection cases associated with solar wind extreme events. A representative number of cases from total profiles are compared with a numerical model to determine the fraction that can be explained by an atmospheric gravity waves (GW). The neutral perturbations on the dayside at 170–190 km altitudes are in excellent agreement with the GW. Whereas, contrary to previous thoughts, neutral perturbations are not necessarily explained by the GW especially on the nightside at 190–210 km. Ion perturbations on the dayside at 170–190 km also show a good agreement with the GW. The agreement becomes extremely low on the nightside at 190–210 km, reaching the limit of strong ion‐neutral coupling around 190 km. Further investigation found that the behavior of the ion perturbations explicitly depends on the dayside and nightside. Its dominant driver potentially differs clearly between dayside and nightside. Statistics of relative perturbations demonstrate a clear effect associated with species scale height in neutrals. Whereas, the correlation between ions and neutrals breaks down at high solar zenith angle near southern dusk. We see currently unexplained behavior that cannot be fully interpreted by GW both at night and near southern dusk. Plain Language Summary: In the upper atmosphere of Mars, both neutral and ionized atmospheres show large amplitude density disturbances that are not seen on Earth. The cause of these disturbances is still unknown; whether they are caused by atmospheric gravity waves (GW) propagating upward from the lower atmosphere or by plasma flows from the sun from space (solar wind; SW) has not yet been determined. We investigated the excitation mechanism of ion perturbations on Mars using the Neutral Gas and Ion Mass Spectrometer onboard NASA's Mars Atmospheric Variability Observatory satellite. We found that on the dayside, neutral atmospheric disturbances are well explained by atmospheric waves. Whereas, contrary to previous ideas, the neutral perturbations cannot always be explained by GW, especially on the night side. The difference in the behavior of ion perturbations between day and night is even more pronounced. While most of the perturbations on the dayside at lower altitudes could be explained by GW, most of the perturbations on the nightside at higher altitudes could not be explained by GW. Our results indicate that the drivers of ionospheric perturbations are potentially different on the day and the night sides. Key Points: We investigated the ionospheric perturbations on MarsThe fraction that can be explained by atmospheric gravity waves differs between day and night sidesWe see unexplained behavior both at night, and southern dusk [ABSTRACT FROM AUTHOR]

Despite ample evidence that extensive water–rock interactions occurred under a CO2-dominated atmosphere on early Mars, carbonate minerals are relatively rare at the surface. One possibility to explain this scarcity is that carbonates were initially abundant, but were later destroyed when atmospheric conditions changed, particularly as a result of volcanism releasing large volumes of sulfur dioxide SO2 into the atmosphere. However, despite some early theoretical and experimental results, no study has investigated the stability of the most common carbonates (Ca, Mg and Fe) in the presence of abundant SO2 gas. Here we present the results of experiments demonstrating that carbonates are systematically unstable when exposed to 0.8 bar of SO2 in moderately oxidizing (SO2 + H2O) or strongly oxidizing (SO2 + H2O + H2O2) environments. In both environments, the reaction end products are systematically sulfates, except for calcium carbonate, which predominantly transforms into calcium sulfite (hannebachite) in moderately oxidizing conditions. Based on these results, carbonates formed early in martian history would have been rapidly decomposed and replaced by sulfates (and sulfites if calcium was abundant enough) in the presence of abundant SO2 released by major volcanic events such as those associated with the build-up of the Tharsis rise. [ABSTRACT FROM AUTHOR]

Recent findings of NO near Gale Crater on Mars have been explained by two pathways: formation of nitric acid (HNO3) in a warm climate or formation of peroxynitric acid (HO2NO2) in a cool climate. Here, we put forth two hitherto unexplored pathways: (a) deposition of nitric/peroxynitric acid onto ice particles in a cold atmosphere, which settle quickly onto Mars' surface and (b) solar energetic particle‐induced production of nitric/peroxynitric acid. The deposition rates are enhanced and NO production is more efficient under the higher atmospheric pressures typical of Mars' ancient atmosphere. Depending on the unknown rate at which nitric/peroxynitric acid is lost from the surface, the new pathways could result in larger NO‐levels than those detected by the Mars Science Laboratory. We predict a 2:1 ratio of nitrite:nitrate would have deposited in cool surface climates with an icy atmosphere, whereas orders of magnitude more nitrate than nitrite is expected from warm surface climates. Plain Language Summary: The nitrogen oxides discovered in present‐day soil on Mars likely formed in the atmosphere before being deposited on the ground. Two possible mechanisms are deposition of nitric acid (HNO3) when Mars had a warm climate and deposition of peroxynitric acid (HO2NO2) during cold climate. The latter scenario involves processes that have not been considered previously and leads to a much faster deposition rate for nitrogen oxides than was reported in previous studies: solar energetic particles splitting N2 in the middle atmosphere, reactions of nitrogen oxides on the surfaces of ice particles in the atmosphere, and deposition of peroxynitric acid onto the Martian surface when surface pressure was higher. Depending on the unknown rate at which they are lost from the surface due to UV photolysis, the maximum accumulation rate for nitrogen oxides could be much larger than is required to explain the present day measurements. We predict that more nitrite would form than nitrate in a cool climate with an icy atmosphere, whereas in a warm climate much more nitrate than nitrite is expected. So, an investigation of the relative amounts of NO2:NO3 in the soil in the present‐day measurements could reveal the climate state under which the salts formed. Key Points: In a cold climate, heterogeneous reactions with atmospheric ice particles would cause faster deposition of HNOx than dry depositionFormation of HNOx species is faster for earlier Martian climates of larger surface pressureModeled NO accumulates to amounts greater than present‐day measurements, so we propose there may be a loss mechanism that is unidentified [ABSTRACT FROM AUTHOR]

A unique event known as the disappearing solar wind (DSW), characterized by an extremely low-density solar wind stream, occurred at Mars on 2022 December 26–27. As this stream flowed past Mars, several properties of the Mars–solar wind interaction changed in response to the density drop. We utilize in situ plasma measurements from the Mars Atmosphere and Volatile EvolutioN spacecraft to examine heavy ion escape during this event. We find that escaping ions with energies above and below 30 eV responded differently to the reduction in solar wind density. High-energy ions experienced a decrease in flux, whereas low-energy ions experienced an increase, regardless of whether they were escaping through the plume or tailward channel. Furthermore, we observe a net reduction in the flux of plume escaping ions during the DSW period, primarily due to a considerable reduction in the high-energy component, which typically dominates plume escape. In contrast, the overall flux of tailward escaping ions increased during this period. These variations in heavy ion escape are mainly attributed to substantial reductions in solar wind dynamic pressure and momentum density. This paper provides new insights into the dynamics of heavy ion escape under an exceptional state of the Mars–solar wind interaction. [ABSTRACT FROM AUTHOR]

The foreshock region filled with turbulences is a natural lab for studying interactions between plasma and waves. The underlying processes are vital for dissipating the energy carried by the solar wind into the Martian environment. In this study, we analyze an ultralow-frequency wave observed on 2015 August 14 by Mars Atmosphere and Volatile Evolution upstream of the Martian bow shock. The wave properties match with those of 30 s waves; the dispersion calculation shows that the upstream plasma was capable of generating the observed waves. The analysis of the ion behaviors implies the wave generated without a field-aligned beam, while the growth rate of waves seems to be modulated by the interplanetary magnetic field conditions. These results indicate the unique role of the Martian foreshock in the interaction between the solar wind and the planet. [ABSTRACT FROM AUTHOR]

Magnetic holes (MHs) are transient magnetic structures responsible for energy conversion in space plasma. Using single-spacecraft measurements from Mars Atmosphere and Volatile EvolutioN (MAVEN), the existence of MHs on Mars has been confirmed. However, due to the limitations of single-spacecraft observations, significant uncertainty also arises on the identification of the spatial scale and 3D geometry of MHs. In this study, we report a series of MHs successively detected by Tianwen-1 near the high-latitude magnetopause and by the MAVEN spacecraft near the subsolar magnetopause. The large separation between Tianwen-1 and MAVEN (∼4 R M) suggests these MHs are macroscale structures extending along the axial direction. Additionally, we observe whistler waves generated by electron perpendicular anisotropy in one of the macroscale MHs. This study is the first joint observation of Martian MHs, shedding light on the research of transient magnetic structures on Mars. [ABSTRACT FROM AUTHOR]

The relatively unconstrained internal structure of Venus is a missing piece in our understanding of the formation and evolution of the Solar System. Detection of seismic waves generated by venusquakes is crucial to determine the seismic structure of Venus' interior, as recently shown by the new seismic and geodetic constraints on Mars' interior obtained by the InSight mission. In the next decade multiple missions will fly to Venus to explore its tectonic and volcanic activity, but they will not be able to conclusively detect seismic waves, despite their potential to detect fault movements. Looking toward the next fleet of Venus missions after the ones already decided, various concepts to measure seismic waves have been proposed. These detection methods include typical geophysical ground sensors already deployed on Earth, the Moon, and Mars; pressure sensors on balloons; and imagers of high altitude emissions (airglow) on orbiters. The latter two methods target the detection of the infrasound signals generated by seismic waves and amplified during their upward propagation. Here, we provide a first comparison between the detection capabilities of these different measurement techniques and recent estimates of Venus' seismic activity. In addition, we discuss the performance requirements and measurement durations required to detect seismic waves with the various detection methods. Our study clearly presents the advantages and limitations of the different seismic wave detection techniques and can be used to drive the design of future mission concepts aiming to study the seismicity of Venus. Plain Language Summary: We do not really know what the interior of Venus looks like. Even the first‐order structure of the size of Venus' core is plagued with large uncertainties. For other planets, such as the Earth and Mars, the interior structure is much better constrained. This is largely thanks to the seismological investigations performed on these planets that revealed their interior structure by studying the seismic waves caused by quakes. In the next decade, new missions will fly to Venus to explore its tectonic and volcanic activity, which is interesting to estimate seismicity. But these missions will not be able to detect any seismic waves. In order to help design future mission concepts, we discuss instruments that could record seismic waves, as already used on the Earth, the Moon, and Mars; instruments on balloons that could float in the Venusian atmosphere; and instruments on spacecrafts that monitor the variations of atmospheric emissions caused by seismic waves originating at the surface. We compare all these different techniques with each other and with recent estimates of Venus' seismic activity to see which of them works best in different scenarios. Key Points: The capabilities of various measurement concepts to detect quakes on Venus are estimated and compared to recent Venus seismicity estimatesGround sensors are limited by their short measurement duration, but also by an atmosphere induced noise that may be above their self noiseAtmospheric seismology concepts are limited to large quake magnitudes, and airglow imagers are favored relative to balloon measurements [ABSTRACT FROM AUTHOR]

Perchlorate is one of the major inorganic pollutants in the natural environment and the living environment, which is toxic to organisms and difficult to degrade due to its special structure. As previously reported, the Phoenix Mars lander detected approximately 0.6% perchlorate in the Martian soil, indicating challenges for Earth-based life to survive there. Currently, biological approaches using dissimilatory perchlorate-reducing bacteria (DPRB) are the most promising methods for perchlorate degradation. However, the majority of DPRB exhibit limited radiation resistance, rendering them unsuitable for survival on Mars. In this study, we obtained the transcriptome data of Deinococcus deserti, and predicted and identified multiple constitutive expression promoters of D. deserti with varying activities. The top-five most active promoters were separately fused to specific genes involved in the degradation of perchlorate from DPRB Dechloromonas agitata CKB, and transformed into Deinococcus radiodurans R1, forming a novel dissimilatory perchlorate-reducing bacterium, R1−CKB. It exhibited both efficient perchlorate degradation capability and strong radiation resistance, potentially offering a valuable tool for the further enhancement of the Martian atmosphere in the future. [ABSTRACT FROM AUTHOR]

In situ resource utilization systems based on cyanobacteria could support the sustainability of crewed missions to Mars. However, their resource-efficiency will depend on the extent to which gases from the Martian atmosphere must be processed to support cyanobacterial growth. The main purpose of the present work is to help assess this extent. We therefore start with investigating the impact of changes in atmospheric conditions on the photoautotrophic, diazotrophic growth of the cyanobacterium Anabaena sp. PCC 7938. We show that lowering atmospheric pressure from 1 bar down to 80 hPa, without changing the partial pressures of metabolizable gases, does not reduce growth rates. We also provide equations, analogous to Monod's, that describe the dependence of growth rates on the partial pressures of CO2 and N2. We then outline the relationships between atmospheric pressure and composition, the minimal mass of a photobioreactor's outer walls (which is dependent on the inner-outer pressure difference), and growth rates. Relying on these relationships, we demonstrate that the structural mass of a photobioreactor can be decreased – without affecting cyanobacterial productivity – by reducing the inner gas pressure. We argue, however, that this reduction would be small next to the equivalent system mass of the cultivation system. A greater impact on resource-efficiency could come from the selection of atmospheric conditions which minimize gas processing requirements while adequately supporting cyanobacterial growth. The data and equations we provide can help identify these conditions. [ABSTRACT FROM AUTHOR]

The Stimson formation is a late‐infilling eolian sandstone in Gale crater, Mars that formed from sand accumulation in a dune field analogous to the modern active Bagnold dune field, enabling a unique opportunity to compare the past to the present dune fields on Mars. Previous work suggested that the Stimson has a coarser grain‐size distribution than the active Bagnold dunes based on three images of the Stimson. We analyze grain size in the Naukluft and Emerson plateaus of the Stimson by observing 115 images throughout the formation to classify textures and quantitatively measuring grains in eight representative individual images. Results indicate that the Stimson has a primary grain size mode at <200 μm. In addition, more than 50% of the observed Stimson rock targets display a coarser grain population with a long‐tailed distribution including grains ∼600–1200 μm. The primary grain size mode is similar to that observed in the Bagnold dunes, but the coarse grain size mode was neither observed in the Bagnold dunes nor in ripples adjacent to the dune field. Models for saltation mechanics indicate that the favored grain size for eolian transport on Mars, ∼100–200 μm, is independent of atmospheric density, though atmospheric density affects the wind speeds at which grains can be transported by winds. We conclude that the source of the Stimson dunes was more proximal and coarser than the source of the Bagnold dunes and that the paleoatmosphere was likely not significantly denser than the modern Martian atmosphere. Plain Language Summary: The Curiosity rover on Mars observed ancient cemented sand‐dune deposits called the Stimson formation near the modern and active Bagnold dunes. These observations provide a unique opportunity to compare past and present environments on Mars. Here, we present measurements of the size of sand grains in the Stimson deposits to compare with previously published measurements of the active Bagnold sands. We minimize bias by using observations from two cameras to find proportionate contributions of texture groups and quantify grain sizes for each texture group. We find that more than half of the images of Stimson deposits contain grains that are coarser than the coarsest grains observed near the modern sand dunes. Previous work hypothesized that these coarser grains could imply that the Stimson dunes formed under either a denser or a thinner atmosphere. We use sediment transport theory and observations to show that the atmosphere was likely similar to modern Mars. Instead, the coarse grains reveal that there must have been a supply of coarse grains nearby when the Stimson dunes formed, likely from eroding riverbeds. Cementation of the Stimson dunes required the presence of liquid water and may thus have required a denser atmosphere, possibly indicating cyclic atmospheric changes through time. Key Points: Comparing ancient and modern windblown sediments enables the study of Mars' eolian environments through timeAbout half of the targets in the Stimson sandstone contain a coarse fraction of grains (>500 μm) that is not observed in the modern Bagnold dunesThe presence of coarse grains in the Stimson necessitates a proximal coarse‐grained source [ABSTRACT FROM AUTHOR]

Abundant geomorphological and geochemical evidence of liquid water on the surface of early Mars during the late Noachian and early Hesperian periods needs to be reconciled with a fainter young Sun. While a dense CO2 ${\mathrm{C}\mathrm{O}}_{2}$ atmosphere and related warming mechanisms are potential solutions to the early Mars climate problem, further investigation is warranted. Here, we complete a comprehensive survey of the warming potential of all known greenhouse gases and perform detailed calculations for 15 different minor gas species under early Martian conditions. We find that of these 15 species, H2O2 ${\mathrm{H}}_{2}{\mathrm{O}}_{2}$, HNO3 ${\mathrm{H}\mathrm{N}\mathrm{O}}_{3}$, NH3 ${\mathrm{N}\mathrm{H}}_{3}$, SO2 ${\mathrm{S}\mathrm{O}}_{2}$, and C2H4 ${{\mathrm{C}}_{\mathrm{2}}\mathrm{H}}_{4}$ cause significant greenhouse warming at concentrations of ∼ ${\sim} $ 0.1 ppmv or greater. However, the most highly effective greenhouse gas species also tend to be more condensable, soluble and vulnerable to photolytic destruction. To provide a reference for future atmospheric evolution and photochemical studies, we have made our warming potential database freely available online. Plain Language Summary: Several billion years ago, geological evidence indicates that Mars was warmer and wetter, with flowing rivers and lakes on its surface. This is hard to explain because the Sun was fainter then, and Mars's orbit is more distant than Earth's. The atmosphere of early Mars was probably thicker, but additional greenhouse gases besides carbon dioxide are needed to provide enough warming. Here we perform a survey of the warming effect of all plausible greenhouse gases on early Mars. We isolate a few species that are particularly effective at warming the planet, calculate how much they raise temperatures at different concentrations, and discuss whether they could have built up to high concentrations in Mars's early atmosphere. Our work provides an important reference for future calculations that incorporate chemistry and other effects. Key Points: We find 15 greenhouse gases capable of providing significant warming on early Mars, of which H2O2, HNO3, NH3, SO2, and C2H4 are the strongestHighly effective trace greenhouse gases also tend to be condensable, soluble and vulnerable to photolysisEthene (C2H4) is a previously unrecognized greenhouse gas that warrants further investigation in the future [ABSTRACT FROM AUTHOR]

Near the Noachian‐Hesperian boundary (∼3.6 billion years ago), most of Mars' near‐surface water inventory was likely frozen in large southern ice sheets and Mars' CO2 atmosphere had eroded enough that it began to periodically collapse. Here, I report model results showing that thermal blanketing of a southern H2O ice sheet by a CO2 ice cap formed during atmospheric collapse would produce melt equivalent to ∼0.2–2.0 × Mars' present‐day global near‐surface H2O inventory. I then model downstream flow, demonstrating the likely development of an ice‐covered fluviolacustrine system with 1,000s‐of‐kilometer‐long rivers, an overtopped Mediterranean‐Sea‐sized lake in Argyre Basin, and substantial water delivery into Margaritifer Terra and potentially Chryse Planitia. This study shows that a steady‐state hydrologic cycle driven by pole‐to‐equator melt and equator‐to‐pole sublimation and atmospheric transport lasting 105–107 year could occur multiple times throughout a ∼108‐year window during which atmospheric pressure was low enough to collapse yet CO2 and H2O inventories and geothermal heat output were high enough to produce substantial meltwater. The nature of this proposed hydrologic cycle is consistent with estimates of the timing, duration, and intermittency of Noachian‐Hesperian fluvial activity. Thus, meltwater release triggered by atmospheric collapse potentially played an important role in the intense pulse of Noachian‐Hesperian fluvial activity: directly so for the Argyre‐Margaritifer‐Chryse system and perhaps indirectly for other catchments. Finally, this study demonstrates that large amounts of water can mobilize in a cold climate, driven by the same atmospheric collapse process occurring on Mars today, without invoking late‐stage warming processes. Plain Language Summary: Approximately 3.6 billion years ago, most of Mars' water was likely frozen in large southern ice sheets and Mars' atmosphere had thinned to the point that it began to collapse, periodically forming a massive south polar CO2 ice cap. I model the thermal blanketing effect of the CO2 ice cap overlying the water ice sheets, demonstrating that it leads to massive meltwater liberation. I also model downstream meltwater, showing that it flowed through 1,000‐km‐long, ice‐covered rivers, filling and then overtopping an ice‐covered lake in Argyre Basin with approximately the volume of the Mediterranean Sea, eventually emptying 8,000 km away into the northern plains. This is the first model that produces enough water to overtop Argyre, consistent with decades‐old geologic observations. Basal melting events likely occurred multiple times, 0.1‐to‐10 million years at a time, during a one‐hundred‐million‐year era about 3.6 billion years ago. Water sublimed downstream likely returned to the south polar cap, perpetuating a pole‐to‐equator hydrologic cycle that may have played an important role in Mars' enigmatic pulse of late‐stage intense fluvial activity. Finally, this study demonstrates that large amounts of water can mobilize in a cold climate without invoking the fraught paradigm of late‐stage climatic warming. Key Points: Collapsing Mars' atmosphere onto an ice sheet ∼3.6 billion years ago can melt and liberate about half of Mars' water inventoryMeltwater feeds an ice‐covered fluviolacustrine system with 1,000s‐km‐long rivers and a breached Mediterranean‐Sea‐sized Argyre Basin lakeThis hydrologic process was likely important for Mars' intense Noachian‐Hesperian fluvial period and does not require late‐stage warming [ABSTRACT FROM AUTHOR]

The Space Physics Data Facility (SPDF) is a digital archive of space physics data and is useful for the storage, analysis, and dissemination of data. We discuss the process used to create an amended dataset and store it on the SPDF. The operational software to generate the archival data software uses the open-source Python package pysat, and an end-user module has been added to the pysatNASA module. The result is the addition of data products to the Mars Global Surveyor (MGS) magnetometer (MAG) dataset, its archival location on SPDF, and pysat compatibility. The primary and metadata format increases the convenience and efficiency for users of the MGS MAG data. The storage of planetary and heliophysics data in one location supports the use of data throughout the solar system for comparison, while pysat compatibility enables loading data in an identical format for ease of processing. We encourage the use of the outlined process for past, present, and future space science missions of all sizes and funding levels. This includes balloons to Flagship-class missions. [ABSTRACT FROM AUTHOR]

The passive monitoring of Martian wind fields is crucial for deciphering the Martian atmosphere. With the 3 strong spectral lines in the 1.27 μm O2(a1Δg) airglow emission band, this article designs the Martian Static Wind Imaging Michelson Interferometer (M-SWIMI) to measure the atmospheric profiles within the altitude range of 10–50 km. Specifically, a forward model to simulate the entire process from the emission transmission through the Martian atmosphere to the eventual formation of the images observed by the instrument is developed. In addition, a robust retrieval algorithm with the bidirectional smoothing (BS) regularization and the multispectral consistency (MC) constraint is proposed. The BSMC algorithm leverages the smoothness of atmospheric parameters in both horizontal and vertical directions and exploits the inherent correlations among different spectral lines, ensuring the accuracy of Volume Emission Rates (VER), temperature and wind. Experimental results demonstrate the superior noise robustness of the retrieval algorithm, supported by comprehensive ablation studies and performance assessments under various noise scenarios, thereby validating the efficacy of the proposed approach in the study of Martian atmospheric dynamics.

Ozone plays a key role in both atmospheric chemistry and UV absorption in planetary atmospheres. On Mars, upper-tropospheric ozone has been widely characterized by space-based instruments. However, surface ozone remains poorly characterized, hindered by the limited sensitivity of orbiters to the lowest scale height of the atmosphere and challenges in delivering payloads to the surface of Mars, which have prevented, to date, the measurement of ozone from the surface of Mars. Systematic measurements from the Martian surface could advance our knowledge of the atmospheric chemistry and habitability potential of this planet. NASA's Mars 2020 mission includes the first ozone detector deployed on the Martian surface, which is based on discrete photometric observations in the ultraviolet band, a simple technology that could obtain the first insights into total ozone abundance in preparation for more sophisticated measurement techniques. This paper describes the Mars 2020 ozone detector and its retrieval algorithm, including its performance under different sources of uncertainty and the potential application of the retrieval algorithm on other missions, such as NASA's Mars Science Laboratory. Pre-landing simulations using the UVISMART radiative transfer model suggest that the retrieval is robust and that it can deal with common issues affecting surface operations in Martian missions, although the expected low ozone abundance and instrument uncertainties could challenge its characterization in tropical latitudes of the planet. Other space missions will potentially include sensors of similar technology. [ABSTRACT FROM AUTHOR]

On 2022‐02‐15, solar eruptions caused one of the most intensive Solar Particle Events (SPEs) in Solar Cycle 25 observed at various heliospheric locations. This study focuses on the enhancements of energetic proton flux observed by multiple detectors located at the orbit and on the surface of Mars. We carry out the first analysis by the Mars Energetic Particle Analyzer (MEPA) instrument on board the Chinese Tianwen‐1 spacecraft (TW‐1) at Mars orbit which also serves to validate the instrument's capability to measure protons of up to 100 MeV. We reconstruct the event spectrum up to 1 GeV and further model the event doses at Mars's orbit and surface which are then validated against the corresponding dosimetry data. Our study utilizes all available radiation detectors at Mars, advances our understanding of Mars's radiation environment induced by large SPEs, and emphasizes the necessity of continuous and synergistic radiation monitoring at Mars. Plain Language Summary: There is a growing interest in exploring Mars in the coming decades. However, a significant obstacle that remains is the presence of space radiation, which poses a considerable and unavoidable threat to crew health, especially during long‐term stays in future Martian habitats. Of particular concern are sporadic energetic particle events caused by strong solar eruptions, which can increase radiation levels in deep space and near Mars to potentially dangerous levels. Notably, a SEP event on 15 February 2022 has caused the first significant radiation enhancement at Mars in Solar Cycle 25 as observed by ESA's Trace Gas Orbiter, Chinese Tianwen‐1 orbiter as well as NASA's Mars Atmosphere and Volatile Evolution spacecraft and the Curiosity rover. By combining data from measurement and modeling techniques, we reconstruct the energy spectrum of this SEP event to understand the potential radiation hazards at Mars. Key Points: A major solar particle event (SPE) was simultaneously measured by multiple detectors both on the surface and in orbit of MarsThe first analysis of a SPE at Mars measured by the Tianwen‐1 Mars orbiter serves to verify its capacity in high‐energy particle detectionWe compare the radiation measurements, both on the surface and in orbit of Mars, with results derived from data‐based models [ABSTRACT FROM AUTHOR]

The Martian atmosphere is characterized by a low density and low speed of sound, which result in the low Reynolds number compressible flows. In this regime, conventional airfoils perform poorly due to the boundary layer separation and the formation of shack wave. The current paper investigates the hovering performance and the structure analysis of a Martian rotor blade built with a triangular airfoil using numerical analysis. The airfoil, with a thickness-chord ratio of t / c = 5% at 30% chord, has been shown through experiments to exhibit non-linear lift enhancement due to the roll-up vortex caused by the sharp leading edge at high angles of attack. The designed blade has a pitch axis of 40% chord, close to the airfoil center of gravity. In order to evaluate the blade thickness distribution along the radial station, Carbon Fiber, due to its high strength-to-weight ratio is applied to the blade. It is found that the main source of stress is inertia force rather than aerodynamic loads and that the blade is structurally safe. Finally, the blade reaches a Figure of Merit of FM = 0.73 at the collective pitch angle of 8 deg and the minimum tensile and compressive factor of safety of 2.90 and 1.74 respectively. [ABSTRACT FROM AUTHOR]

The Evolutionary aLgorithm for Iterative Studies of Aeromechanics (ELISA) was developed in support of the Rotorcraft Optimization for the Advancement of Mars eXploration (ROAMX) project. ELISA was developed to enable aerodynamic rotor hover optimization for low Reynolds number flows in the Mars atmosphere. The first module of the algorithm allows for unconventional airfoil parameterization and multiobjective airfoil geometry optimization using OVERFLOW. The Pareto-optimal airfoil sets are converted to a set of Pareto-optimal airfoil decks, providing the lowest drag airfoil geometry for each angle of attack. The second module allows for rotor geometry optimization with simultaneous maximization of blade loading and minimization of rotor power using the comprehensive analysis CAMRADII. The result is a Pareto-optimal rotor set, providing the lowest power rotor for each attainable blade loading, and one of the first tools for hover-optimized rotors for high-subsonic low Reynolds number conditions. The airfoil thickness can be modified after the airfoil optimization is complete, allowing for a post-airfoil optimization adjustment of blade thickness to facilitate conforming to external structural analysis requirements. The relevance of the code is demonstrated with case studies for the ROAMX rotor optimization for Ingenuity-sized single rotors in the Mars atmosphere and a performance study optimizing the chord and twist of Ingenuity's coaxial rotor resulting in the Sample Recovery Helicopters candidate rotor. [ABSTRACT FROM AUTHOR]

Space exploration and research are uncovering the potential for terrestrial life to survive in outer space, as well as the environmental factors that affect life during interplanetary transfer. The presence of methane in the Martian atmosphere suggests the possibility of methanogens, either extant or extinct, on Mars. Understanding how methanogens survive and adapt under space-exposed conditions is crucial for understanding the implications of extraterrestrial life. In this article, we discuss methanogens as model organisms for obtaining energy transducers and producing methane in a simulated Martian environment. We also explore the chemical evolution of cellular composition and growth maintenance to support survival in extraterrestrial environments. Neutral selective pressure is imposed on the chemical composition of cellular components to increase cell survival and reduce growth under physiological conditions. Energy limitation is an evolutionary driver of macromolecular polymerization, growth maintenance, and survival fitness of methanogens. Methanogens grown in a Martian environment may exhibit global alterations in their metabolic function and gene expression at the system scale. A space systems biology approach would further elucidate molecular survival mechanisms and adaptation to a drastic outer space environment. Therefore, identifying a genetically stable methanogenic community is essential for biomethane production from waste recycling to achieve sustainable space-life support functions. [ABSTRACT FROM AUTHOR]

The atmosphere of Mars has been studied for many years now by a long series of missions. The paper focuses on the results obtained by two of these that are led by European researchers overseen by the European Space Agency, i.e., Mars Express which was launched in 2003 and ExoMars Trace Gas Orbiter launched in 2016. Both missions are still providing high-quality data about the atmosphere of Mars, such as abundances of its key species – CO2, CO, H2O, O3 - playing an important role in the different cycles existing on the planet, as well as other trace gases – O2 (mixing ratio of 3.1 to 5.8 × 10−3 above 90 km), the recently discovered HCl (up to 4 ppbv below 30 km), and the elusive CH4 (stringent detection limit of 20 pptv). Some instruments are also sensitive enough to provide information on isotopologues of the key elements and have delivered for some of these the first and unique vertical profiles available today ( δ 13 C and δ 18 O in CO2 and CO, D/H, δ 17 O and δ 18 O in water vapour). The paper retraces the history of the exploration of the Martian atmosphere putting the results from both missions in perspective. [ABSTRACT FROM AUTHOR]

Understanding the interaction between Mars and the solar wind is crucial for comprehending the atmospheric evolution and climate change on Mars. To gain a comprehensive understanding of the Martian plasma environment, global numerical simulations are essential in addition to spacecraft observations. However, there are still discrepancies among different simulation models. This study investigates how these discrepancies stem from the considered physical processes and numerical implementations. We compare two global multispecies MHD models: the "Sun model" based on the BATS‐R‐US code and the "Sakata model" based on a newly developed multifluid model MAESTRO. By employing the same typical upstream conditions and the same neutral atmosphere for current Mars, along with similar numerical implementations such as inner boundary conditions, we obtain simulation results that exhibit unprecedented agreement between the two models. The dayside results are nearly identical, especially along the subsolar line, indicating the robustness of MHD models to predict dayside interaction under given upstream conditions and ionosphere assumptions. The escape rates of planetary ions are also in good agreement. However, discrepancies remain in the terminator and nightside regions. Detailed numerical implementations, including inner boundary conditions, magnetic field divergence control methods, and radial resolutions, are shown to influence certain aspects of the results greatly, such as magnetotail configuration and ion diffusion. Key Points: The same physical assumptions are employed for two different global multispecies MHD modelsThe results for the dayside interaction and planetary ion escape are in unprecedented good agreementDetails of the numerical implementations influence the results, especially on the nightside [ABSTRACT FROM AUTHOR]

This study presents the development of a so‐called Turbulent Kinetic Energy (TKE)‐l, or TKE‐l, parameterization of the diffusion coefficients for the representation of turbulent diffusion in neutral and stable conditions in large‐scale atmospheric models. The parameterization has been carefully designed to be completely tunable in the sense that all adjustable parameters have been clearly identified and the number of parameters has been minimized as much as possible to help the calibration and to thoroughly assess the parametric sensitivity. We choose a mixing length formulation that depends on both static stability and wind shear to cover the different regimes of stable boundary layers. We follow a heuristic approach for expressing the stability functions and turbulent Prandlt number in order to guarantee the versatility of the scheme and its applicability for planetary atmospheres composed of an ideal and perfect gas such as that of Earth and Mars. Particular attention has been paid to the numerical stability and convergence of the TKE equation at large time steps, an essential prerequisite for capturing stable boundary layers in General Circulation Models (GCMs). Tests, parametric sensitivity assessments and preliminary tuning are performed on single‐column idealized simulations of the weakly stable boundary layer. The robustness and versatility of the scheme are assessed through its implementation in the Laboratoire de Météorologie Dynamique Zoom GCM and the Mars Planetary Climate Model and by running simulations of the Antarctic and Martian nocturnal boundary layers. Plain Language Summary: In planetary atmospheres, turbulent motions actively contribute to the mixing of quantities such as heat, momentum, and chemical species. Such motions are not resolved in coarse‐grid atmospheric models and have to be parameterized. The parameterization of turbulent mixing should ideally be based on physical laws and sufficiently sophisticated to realistically represent the full spectrum of motions over the full range of stability encountered in the atmospheres. However, it also necessarily contains a number of closure parameters not always well identified and whose values are determined empirically—thereby questioning the universality of the parameterization and its potential application over the full globe or even to other planets—or adjusted to guarantee the numerical stability of the model. This study presents the design of a turbulent mixing parameterization that can be fully calibrated and applied in planetary atmospheres such as that of Mars. We then calibrate the parameterization on an idealized simulation set‐up and test its robustness and performance by running simulations of the Antarctic and Martian atmospheres. Key Points: A simple TKE‐l turbulent diffusion scheme is developed in a semi‐heuristic way for applications in models of the Earth and Mars atmospheresAll adjustable parameters are clearly identified and the number of parameters is minimized to thoroughly assess the parametric sensitivityOnce tuned on GEWEX Atmospheric Boundary Layer Study 1 1D simulations, the scheme is able to capture the Antarctic and Martian stable boundary layers in 3D simulations [ABSTRACT FROM AUTHOR]

A dual-wavelength spaceborne Martian polarized wind imaging Michelson interferometer based on liquid crystal tunable filters (LCTF-MPWIMI) has been proposed for the remote sensing detection of dynamic parameters such as wind speed and temperature in the middle and upper atmosphere of Mars. Using the detected Martian oxygen atom emission lines at 557.7 nm and 630.0 nm as observation spectral lines, this technology extends the detection altitude range for Martian atmospheric wind speed and temperature to 60–180 km. By leveraging the different spectral line visibility of the interferograms at the two wavelengths, a novel method for measuring Martian atmospheric temperature is proposed: the dual-wavelength spectral line visibility product method. This new approach reduces the uncertainty of temperature detection compared to traditional single spectral line visibility methods, while maintaining the precision of wind speed measurements. The feasibility of the LCTF-MPWIMI for measuring wind and temperature fields in the Martian middle and upper atmosphere has been validated through theoretical modeling and computer simulations. The interferometer, as a key component of the system, has been designed and analyzed. The proposed LCTF-MPWIMI instrument is free of mechanical moving parts, offering flexible wavelength selection and facilitating miniaturization. The dual-wavelength temperature measurement method introduced in this work provides superior temperature measurement precision compared to any single spectral line when the signal-to-noise ratio (SNR) of the interferograms is comparable. Moreover, this method does not impose specific requirements on the atomic state of the spectral lines, making it broadly applicable to similar interferometric wind measurement instruments. These innovations offer advanced tools and methodologies for measuring wind speeds and temperatures in the atmospheres of Mars and other planets. [ABSTRACT FROM AUTHOR]

A climatological survey of Martian ionospheric plasma density irregularities was conducted by exploring the in-situ measurements of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. The irregularities were first classified as enhancement, depletion, and oscillation. By checking the simultaneous magnetic field fluctuation, the irregularities have been classified into two types: with or without magnetic signatures. The classified irregularities exhibit diverse global occurrence patterns, as those with magnetic signatures tend to appear near the periphery of the crustal magnetic anomaly (MA), and those without magnetic signatures prefer to appear either inside of the MA or outside of the MA, depending on the type and solar zenith angle. Under most circumstances, the irregularities have a considerable occurrence rate at altitudes above the ionospheric dynamo height (above 200 km), and the magnetization state of the ions seems irrelevant to their occurrence. In addition, the irregularities do not show dependence on magnetic field geometry, except that the enhancement without magnetic signatures favors the vertical field line, implying its equivalence to the localized bulge. Other similarities and discrepancies exist in reference to previous studies. We believe this global survey complements previous research and provides crucial research clues for future efforts to clarify the nature of the Martian ionospheric irregularities. [ABSTRACT FROM AUTHOR]

The installation of planetary and lunar human outposts might be an important step for future solar system exploration by both public space agencies and private companies. Humans living and working in these artificially created habitats will possibly depend, among other life support approaches, on bio-regenerative life support systems to produce and recycle oxygen and water, and to produce food. A variety of natural resources suitable life support can be readily found on Mars, and to a lesser extent on the Moon. Instead of launching all resources (e.g., water, propellant, food and other materials) from Earth, it could potentially be much more cost effective to send automated machinery to harvest resources from the Martian surface and atmosphere in preparation for the arrival of humans. The exploration of these natural resource deposits, the concentration of the raw materials contained in them, and the feasibility of mining and refinement are open questions that require further consideration. Here we address the concept of harvesting resources in situ by reviewing the potential of several large deposits of hydrated minerals found on the surface of Mars thanks to previous orbital detections. We also present estimates of water volumes potentially retrievable from specific deposits and describe additional uses of the hydrated minerals for example as fertilizer for food production. • Hydrated sulfate deposit contains important resources for landed crews. • Bio-regenerative Life-Support Systems could reduce logistics from Earth to Mars. • Several regions on Mars bear large exploitable resource potential. • Water is abundantly available in selected deposits. • Prolonged human presence on Mars could profit from the use of local resources. [ABSTRACT FROM AUTHOR]

The Mars Sample Return (MSR) campaign is one of the most ambitious and complex planetary science exploration missions ever pursued. With the participation of NASA, ESA, and many industry partners, MSR aims to bring Martian rock and atmosphere samples to Earth with the goal of answering key questions about Mars' geological, climatological and, potentially, biological evolution. To accomplish this ambitious goal, the MSR campaign relies on three distinct flight elements and a ground element. The Earth Return Orbiter mission that would host the Capture, Containment, and Return System (CCRS) is the last flight element of the trio. The mission would capture the orbiting sample in low Mars orbit (launched into orbit by another mission), contain it, and return it to Earth, landing at the Utah Test and Training Range. Since its early architecture, several changes were adopted by CCRS to improve overall payload efficiency and reduce mass. This paper will discuss the CCRS design, how the current CCRS architecture contributes to an improved mission concept, and the next critical steps of the mission toward its launch. • MSR is one of the most ambitious and complex exploration missions ever pursued. • CCRS is the last flight element of MSR bringing the Mars samples to Earth. • Detailed examination of the NASA CCRS payload is presented. • Insight into the operational plans of CCRS that enables a successful sample return. • Contributes to the broader body of knowledge in space exploration. [ABSTRACT FROM AUTHOR]

As a payload of Tianwen-1 (TW-1), the Mars Mineral Spectrometer (MMS) is tasked with acquiring hyperspectral data of the Martian surface to detect material composition. Microdeformations in optical, mechanical, and thermal components result in the MMS experiencing spectral response distortion in orbit, leading to systematic changes in pixel central wavelengths and full width at half maximum (FWHM). Known as the spectral smile, this distortion compromises the accuracy of reflectance inversion and material composition detection. This study introduces a method for detecting the spectral smile through the Martian atmospheric absorption channel, capitalizing on the distinct characteristics of the atmospheric composition and absorption patterns of Mars. A suitable technical route for in-orbit spectral smile detection was established and tested using simulation experiments and MMS-acquired hyperspectral data. Results suggest that the proposed method can attain central wavelength shifts with a maximum error of 0.32 nm and FWHM variations with a maximum error of 1.95 nm. Employing in-orbit spectral smile detection markedly enhances the correction of Martian atmospheric absorption and provides technical support for Martian surface reflectance inversion. https://github.com/wubingnote/MMS-Spectral-Smile. [ABSTRACT FROM AUTHOR]

Aerobraking represents a valuable option for interplanetary missions thanks to its capability of reducing the orbital semi-major axis through multiple atmospheric passages, thus with limited fuel consumption. However, due to structural and thermal loads the spacecraft undergoes, mission risks and ground operations costs increase. This study aims to tackle this aerobraking drawback by enhancing its autonomy. The main activities required for aerobraking execution, including atmospheric prediction, orbital state estimation, and orbit control, are tailored for onboard execution. Regarding orbit control, two different methodologies, differentiated by working principle and prediction horizon breadth, are investigated. The first plans orbit control manoeuvres based on the prediction of the atmospheric conditions for a single upcoming pericentre, while the second schedules and optimizes the manoeuvres considering the recent atmospheric conditions experienced by the spacecraft and the altitude trend of multiple upcoming pericentres. The whole operational concept is tested within a simulated environment, with the primary objective of accurately reproducing the intense atmospheric variations of the Martian atmosphere, which represents the most challenging aspect during aerobraking execution. The numerical testing, involving the simulation of different aerobraking regimes under varied conditions, shows that the natural dynamics of the orbital motion can be exploited to minimize both fuel consumption for orbit control manoeuvres and spacecraft load variations, thus enabling more efficient aerobraking and more stable flight conditions, even with the limited predictive capabilities that characterize onboard resources. Both control logics permit the aerobraking execution without exceeding the maximum allowed thermal limits, hence showing their effectiveness. Furthermore, a Monte Carlo analysis conducted on a complete aerobraking simulation reveals a 25.5% reduction in propellant consumption and a 9.4% reduction in heat rate variability when the orbit control decision process uses information relative to multiple future pericentres. [ABSTRACT FROM AUTHOR]

Morphological characteristics were measured for barchan dunes on Earth (2,686 dunes in 30 barchan fields) and Mars (720 dunes in 10 barchan fields) using satellite images. The data were used to (a) develop a new barchan classification system; (b) compare characteristics of barchans on Earth and Mars; and (c) assess whether barchans, in bulk, display allometric or scale‐invariant characteristics. Dimensional metrics were obtained for the width and length of barchan bodies, the width and length of barchans including the horns, and the length of each horn. Dimensionless metrics were derived for the ratios of the body width to the width between the tips of the horns (width ratio), the length of the entire barchan to the length of the body (length ratio), and the length of the longer horn to the shorter horn (symmetry ratio). The width, length, and symmetry ratios were used to classify barchans into eight types and compare the characteristics of their distributions on the two planets. From this analysis, it was established that, statistically, barchans on Earth are distinctive from those on Mars based on the morphometrics, with terrestrial barchans being, on average, of smaller size and more often symmetrical, while Martian barchans more often have convergent horns that are short relative to the central dune body and are more often asymmetrical. The analysis further reveals that barchan planform morphology can be considered scale‐invariant, and we argue that body width is the most appropriate measure representing barchan size. Plain Language Summary: Crescent‐shaped sand dunes (barchans) are widely found on Earth and Mars. Relative variations in the shape of these bedforms are thought to reflect differences in the planetary sand transport environment in terms of sand flux magnitudes, transport modes, and wind climate (speeds and directional variability). Comparing the shapes of barchans on Mars with those on Earth can generate hypotheses on how and why sand transport conditions and dune formation under the Martian atmosphere may be different. Satellite imagery analysis of 3,406 barchan dunes on both planets yields insights on planform dimensions (width and length of the dune body, lengths and divergence of the horns) as well as three shape indices (Width Ratio, Length Ratio, Symmetry Ratio) that were used to derive a classification of eight barchan types. Analysis shows that average barchan planform geometry displays fixed proportions over several orders of magnitude in size (scale‐invariance). Significant relative differences are apparent between the two planets, with barchans on Mars generally being much larger in absolute size but having shorter, more convergent and asymmetric horns than barchans on Earth. The study further suggests that the transverse width of the dune body is the best measurement to reflect the overall size of a barchan. Key Points: A classification of barchan types is derived by applying three morphometric indices to 3,406 dunes on Earth and MarsBarchan planform morphology can be considered a scale‐invariant property over orders of magnitudeDifferences in relative morphology reflect differences in planetary sand transport conditions and dune formation [ABSTRACT FROM AUTHOR]

The Tropical Cloud Oscillation (TCO) in the Martian atmosphere is a shift of clouds in the northern spring and summer tropical cloud belt between the eastern and western hemispheres on an intra‐seasonal timescale of about 10–40 sols. The TCO is a significant intraseasonal variation and may strongly affect the Martian general circulation, water cycle, and dust cycle. We examine TCOs using multiple data sets with a focus on the clouds observed in Mars Daily Global Maps during Mars Year (MY) 29–35. One or more TCO cycles are observed in each MY and the phenomenon is most prominent during Ls = 135°–185°. Space‐time spectral analysis shows a variety of waves which appear to follow the theoretical dispersion relationships of equatorial waves, such as Kelvin waves, Rossby waves, and Mixed Rossby Gravity waves. The TCO appears to be controlled by zonal wavenumber one traveling waves with Kelvin and Rossby wave characteristics and exhibits a fine‐scale latitudinal structure that requires modeling with sufficient resolution. Issues with current data assimilation products for use in studies of Martian equatorial waves due to this fine‐scale structure are discussed. Plain Language Summary: During martian northern spring and summer, a relatively thick water ice cloud belt is observed in the tropics (approximately 25°S–25°N), which modifies large‐scale circulation, global water transport and the atmospheric dust cycle. We report on a Tropical Cloud Oscillation (TCO) that is a periodic shift in the thickness of this cloud belt between the eastern and western hemispheres on timescales (about 10–40 Mars days) longer than that of weather but shorter than that of seasons. Since the TCO involves changes in clouds and implies changes in circulation, it may also modulate the dust and water cycles. We examine TCOs using image data for Mars Year 29–35 (late 2007 through early 2021). One or more TCO cycles are observed in each Mars Year and the phenomenon is most prominent in late northern summer. A wide variety of atmospheric waves are found during TCOs; however, the most important are equatorial waves traveling eastward and westward with one peak and one trough around the planet. These waves have narrow latitudinal length scales and thus require high resolution numerical models to simulate and properly represent in data assimilation products. Key Points: The Martian tropical cloud belt exhibits eastern—western zonal oscillations that are most prominent in late northern summerTropical Cloud Oscillations are controlled by large‐scale low frequency equatorial Kelvin and Rossby wavesEquatorial wave dynamics may have an important effect on the Martian water and dust cycles [ABSTRACT FROM AUTHOR]

Our understanding of the paleoclimate of Mars and the dominant forcing functions that drive large‐scale changes largely remains a mystery. However, the Martian Polar Layered Deposits (PLD) offer a promising avenue for unraveling the planet's recent paleoclimate history. Despite recent progress to detect a climate signal in the PLD, definitive evidence of a correlation between the stratigraphic record and Mars' recent orbital history remains elusive. We utilized new and updated techniques, including high‐resolution stratigraphic reconstruction from High Resolution Imagine Science Experiment stereo imagery and digital terrain models, combined with a technique of variable dip correction to account for three dimensional bedding orientations. Signal processing methods, such as wavelet and Fourier analysis, were applied to perform detailed time‐series analysis. These analyses revealed a quasi‐periodic signal indicative of fine bedding at a scale of approximately 2 m. Based on previously proposed deposition rates, these fine layers appear to correspond to timescales centering around 4,000 years. This suggests that the meter‐scale layers may not be the result of orbital forcing and hint at an unknown sub‐Milankovitch climate forcing mechanism. We discuss potential exogenic causal mechanisms, such as cyclic variations in solar activity, and endogenic factors, including large‐scale changes in dust distribution. Understanding the formation processes of these fine layers may significantly enhance our knowledge of Martian climate history and its driving forces. Plain Language Summary: In this paper, we investigate the presence, distribution, and significance of small‐scale layers in the northern polar layered deposits (PLD) of Mars. Solar radiation is a key variable in determining the long‐term evolution and stability of the polar caps, and it is closely linked to changes in the planet's orbit, such as precession, eccentricity, and obliquity. We argue that the thickness and periodicity of these fine layers reflect a causal mechanism that cannot be attributed solely to climate changes resulting from the long‐term evolution of Mars' orbit. Based on proposed accumulation rates of the polar ice, we suggest that the quasi‐periodic bedding may represent a climate signal occurring on timescales several orders of magnitude shorter than those of the orbit changes in Mars, centering around 4,000 years. These observations help to characterize and better understand the PLD and their formation. Key Points: Meter‐scale bedding is widespread throughout Mars northern polar layered depositsUsing image and topographic data, we show that the fine bedding is quasi‐periodic within a confined range of wavelengths from 1.5 to 3 mUnder previous deposition rate estimates, meter‐scale bedding corresponds to ∼ ${\sim} $4,000‐year, sub‐Milankovitch timescales [ABSTRACT FROM AUTHOR]

Characterizing the exchange of water between the Martian atmosphere and the (sub)surface is a major challenge for understanding the mechanisms that regulate the water cycle. Here we present a new data set of water ice detected on the Martian surface with the Thermal Emission Imaging System (THEMIS). The detection is based on the correlation between bright blue‐white patterns in visible images and a temperature measured in the infrared that is too warm to be associated with CO2 ${\mathrm{CO}}_{2}$ ice and interpreted instead as water ice. Using this method, we detect ice down to 21.4°S, 48.4°N, on pole‐facing slopes at mid‐latitudes, and on any surface orientation poleward of 45° latitude. Water ice observed with THEMIS is most likely seasonal rather than diurnal. Our data set is consistent with near‐infrared frost detections and predictions by the Mars Planetary Climate Model. Water frost average temperature is 170 K, and the maximum temperature measured is 243 K, lower than the water ice melting point. Melting of pure water ice on the surface is unlikely due to cooling by latent heat during its sublimation. However, 243 THEMIS images show frosts that are hot enough to form brines if salts are present on the surface. The water vapor pressure at the surface, calculated from the ice temperature, indicates a dry atmosphere in early spring, during the recession of the CO2 ${\text{CO}}_{2}$ ice cap. The large amount of water vapor released by the sublimation of warm frost cannot stabilize subsurface ice at mid‐latitudes. Plain Language Summary: During spring, parts of the Martian surface at mid and high latitudes are covered by a thin, bright layer of frost. Some of these ice deposits are made of CO2 ${\text{CO}}_{2}$ ice, but some frosts have a temperature that is too warm to be CO2 ${\text{CO}}_{2}$ frosts and are thus constituted of water ice that forms in winter and sublimes in spring. We conducted a spatial and temporal mapping of these ice deposits using the camera THEMIS onboard the Mars Odyssey orbiter to better characterize the exchange of volatiles between the Martian atmosphere and the surface. Water ice is preferentially detected on pole‐facing slopes rather than flat surfaces below 45° latitude and all types of surfaces at higher latitudes. In late spring, water ice cannot melt despite solar heating because it cools down with the release of latent heat. On the other hand, these ice deposits are warm enough to form brines if salt crystals are present at the surface. When the frost sublimes, it serves as a source of water vapor that can diffuse into the ground and recondense to stabilize the permafrost below the surface. However, this effect is not sufficient to stabilize subsurface ice at low latitudes. Key Points: Seasonal water frosts on Mars are identified with coincident visible and temperature data obtained with THEMIS poleward of 48°N and 21°SWater frosts remain too cold to melt as pure ice. However, the warmest frost deposits observed may co‐exist with brinesWarm water frost, which releases a large amount of water vapor when it sublimates, cannot stabilize the low‐latitude subsurface ice [ABSTRACT FROM AUTHOR]

The Martian ionosphere has many similarities and differences compared to Earth, attracting significant attention. This paper utilizes radio occultation data from the Mars Global Surveyor (MGS), Mars Atmosphere and Volatile Evolution Mission (MAVEN), and ESA Mars Express mission (MEX), associated with the measurements from Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) aboard MEX, to investigate the seasonal variation of the Martian dayside ionosphere. Data preprocessing is performed first to isolate the influence of solar zenith angle and solar radiation, the seasonal variation of the Martian dayside ionosphere explored in this study. The results suggest that the peak electron density reaches its minimum and maximum at LS = 70.2° and LS = 250.2°, respectively, with an amplitude of 16.5% concerning the average (LS is referred to as the solar longitude of Mars). The peak altitude experiences its minimum at LS = 78.4° and maximum at LS = 258.4°, and its relative amplitude is 12.1%. The outcomes suggest that the seasonal variations in the Martian ionosphere are primarily attributed to the Mars‐Sun distance change, which is different from the situation on Earth. This study will benefit both Martian ionosphere modeling and Earth's ionosphere understanding in the future. Plain Language Summary: The Martian ionosphere shares many similarities with Earth's, which has attracted considerable attention. The Martian ionosphere is primarily driven by solar radiation, including the solar zenith angle and solar radiation strength. So far, missions of MGS, MEX, and MAVEN have collected thousands of measurements about the Martian ionosphere over decades. Based on data preprocessing and systematic error correction, this study explored the seasonal variation in the dayside Martian ionosphere's peak electron density and altitude. The primary results suggest that the seasonal variation in the Martian ionosphere is mainly driven by the Sun‐Mars distance changing, and the mechanisms are distinguished for peak electron density and altitude. In particular, the peak electron density is directly driven by solar radiation, while the peak altitude is due to the lower boundary perturbation. These findings are quite different from Earth and shed light on further understanding in the future. Key Points: The seasonal variability of the Martian dayside ionosphere is studied using multi‐source dataBoth the peak electron density and peak altitude exhibit notable seasonal variationsThe mechanisms are different between the seasonal variations in the peak electron density and altitude [ABSTRACT FROM AUTHOR]

A comprehensive modeling study has been conducted to investigate space weather effects at Mars during the 10 September 2017 solar flare, utilizing an integrated framework that combines the global magnetohydrodynamic (MHD) model and Mars Global Ionosphere‐Thermosphere Model (MGITM). This is the first time the thermosphere‐ionosphere‐magnetosphere system is self‐consistently simulated under realistic, time‐varying conditions. Our simulations align well with observations from the Mars Atmosphere and Volatile EvolutioN (MAVEN). Recognizing that complexities due to highly disturbed upstream conditions and rotating crustal fields obscure solar flare effects in orbit‐to‐orbit comparisons, we perform controlled simulations of nonflare and flare cases and exploit their contrast to quantify spatiotemporal variations in flare impact. Our results highlight pronounced and rapid dayside ionospheric perturbations, contrasting with weaker and delayed nightside responses. Notably, in the topside ionosphere, O2+ ${\mathrm{O}}_{2}^{+}$ and CO2+ ${\mathrm{O}}_{2}^{+}$ densities increase primarily on the dayside below ∼ ${\sim} $300 km altitude, peaking with an increase of 20%–30%. The O+ ${\mathrm{O}}^{+}$ density shows a more significant increase of up to ∼ ${\sim} $50%, extending into the magnetosphere and nightside via plasma transport, increasing its total loss rate by 14%. We observe distinct altitude‐dependent patterns in dayside electron density enhancements in percent, characterized by a weakening with altitude and a rapid decay below ∼ ${\sim} $150 km in line with the flare development, and a gradual intensification between ∼ ${\sim} $150–300 km due to plasma transport and flare‐induced atmospheric upwelling. Earlier Mars Global Surveyor observations were limited to the low‐altitude pattern due to atmospheric expansion and missed the higher altitude variations observed by MAVEN. Plain Language Summary: This study investigates the impact of a powerful X8.2‐class solar flare on 10 September 2017 at Mars. Using an integrated modeling framework that combines two state‐of‐the‐art global models, our simulations provide insights into distinct altitude‐dependent patterns of flare‐induced ionospheric density enhancements, pronounced day‐night asymmetry, and a moderate increase in ion escape. Key findings include rapid variations in ionospheric density enhancements at lower altitudes, with a gradual intensification at higher altitudes due to plasma transport and atmospheric upwelling. These findings contribute to a better understanding of how solar flares impact the space environment of unmagnetized or weakly‐magnetized planets like Mars. Key Points: The solar flare causes pronounced and rapid dayside ionospheric perturbations and weaker and delayed effects on the nightsideO2+ and CO2+ densities increase by 20%–30% above 150 km on the dayside, while O+ increases by up to 50% and over larger spacePercentage increase of dayside e− densities decreases with altitude and decays fast below ∼150 km, and rises and decays slowly above that [ABSTRACT FROM AUTHOR]

The Mars Sample Return campaign is an endeavor of unprecedented technological complexity and coordination that attempts to answer fundamental questions about the habitability of Mars by returning the first samples of Martian material to Earth for analysis. The third mission in the campaign consists of the NASA-provided Capture, Containment, and Return System (CCRS) onboard the European Space Agency's Earth Return Orbiter, which will retrieve the Orbiting Sample (OS) container from its orbit around Mars. Retrieving a passive sample container from a planetary orbit has never been attempted by any spacecraft and requires the development of new technology to succeed in this ambitious task. This paper introduces the high-reliability Capture Sensor Suite (CSS), a novel optical detection system that provides CCRS with the capability to autonomously detect the OS as it is captured. This article will discuss the challenges and requirements for the fault-tolerant design of the CSS. [ABSTRACT FROM AUTHOR]