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Supersonic flows around parachute two-body systems are numerically investigated by solving the compressible Navier-Stokes equations. In the present study, both rigid and flexible parachute models are considered, which comprise a capsule and a canopy. The objective of the present study is to investigate the effects of the Martian atmosphere on the unsteady flows produced by these parachute two-body models and the structural behavior of the flexible canopy. It was found that in the Martian atmosphere, the supersonic rigid parachutes with shorter trailing distances exhibited weaker aerodynamic interactions between the capsule wake and canopy shock, resulting in a smaller pressure distribution on the typical surfaces of the canopy. By contrast, because the flow modes around the flexible parachute in the Martian atmosphere were similar to those of the rigid parachute under the air conditions of the wind tunnel tests, the canopy shape was almost unchanged. When a new canopy material was designed by decreasing the Young’s modulus and damping coefficient, an area oscillation phenomenon was observed in the flexible parachute with a trailing distance of 10 in the Martian atmosphere. Consequently, the Martian atmosphere (low density and pressure) has a significant effect on the aerodynamic performance of the flexible parachute system.

The European Space Agency flew an entry, descent, and landing demonstrator module called Schiaparelli that entered the atmosphere of Mars on 19 October 2016. The entry and descent instrumentation s...

STORM is a general semi-analytical propagation code developed at Airbus Defence and Space and originally designed to perform long-term Mars orbit simulations, for mission analysis purposes. Since the 1960’s, humans have sent 18 spacecraft to study the Red Planet, 8 of which are active as of February 2021. While space-debris surveillance and mitigation have been gathering momentum in the past decades in the case of Earth, the issue of artificial objects left in orbit around Mars is another cause for concern in view of the Committee of Space Research’s Planetary Protection Policy. In that perspective, STORM is introduced as a potential tool for assessing the compliance of spacecraft with orbital lifetime requirements. The programme makes it possible to study the evolution of orbits over several decades by propagating a set of mean equinoctial orbital elements, with a comprehensive set of gravitational and non-gravitational perturbations. Particular emphasis is laid on atmospheric entry cases as the programme is interfaced with the European Mars Climate Database, which is the current best knowledge of the state of the Martian atmosphere. This work is focused on the semi-analytical propagator’s implementation and its actual use for predicting entry dates. A sensitivity analysis is conducted to ascertain the influence of atmosphere modelling and initial conditions, providing insight into how to account for uncertainties in a probabilistic way.

We consider a linearized dynamic system, which determines the motion of the spacecraft relative to the center of mass in a rarefied atmosphere of Mars in the non-resonant case. This dynamic system takes into account the influence of disturbances from small aerodynamic and inertial asymmetry. The aim of this paper is to synthesis approximate optimized continuous control of the angular velocity and spatial angle of attack of the spacecraft with small aerodynamic and inertial asymmetries in the atmosphere of Mars, implemented by means of four onboard jet engines. The averaging method and method of dynamic programming are applied in control synthesis. The main result of this work is to obtain expressions of approximate continuous control of the angular velocity and spatial angle of attack of the spacecraft with small aerodynamic and inertial asymmetries in the atmosphere of Mars. These expressions provide a controlled decrease of the angular velocity and spatial angle of attack to small magnitudes. In addition, the paper contains brief descriptions of several control algorithms based on the application of the obtained laws of the spacecraft attitude control. The reliability of the obtained control laws is confirmed by results of numerical modeling of a descent motion of the asymmetric spacecraft Mars Polar Lander in the rarefied atmosphere of Mars.

On 26 November 2018, the Interior Exploration Using Seismic Investigations, Geodesy and Heat Transport (InSight) lander successfully touched down on the surface of Mars. Over its more than seven ye...

China’s Mars exploration mission has stimulated tremendous interest in planetary science exploration recently. To propose potential scientific research projects, this study presents a concept simulation for the measurement of Martian atmospheric winds using the Doppler Michelson interferometry technique. The simulation is based on the satellite instrument initially designed for the Dynamic Atmosphere Mars Observer (DYNAMO) project to measure vertical profiles of winds from the 1.27 μm airglow observations in the Martian atmosphere. A comprehensive DYNAMO measurement simulation forward model based on an orbit submodel, an atmospheric background field submodel, and an instrument submodel is developed using the Michelson equation. The simulated interferogram signal over the field of view (FOV) calculated by the forward model is associated with the filter transmittance function, column emission rate of airglow, wind velocity, temperature, and the Michelson phase. The agreement between the derived atmospheric signals from the simulated interferogram without altitude inversion and the input parameters used to initiate the forward model confirms the validity of the forward model.

We present the kinetic Monte-Carlo model, which was developed to describe the influence of a proton flux from the undisturbed solar wind on the daytime atmosphere of Mars. For the first time, the degradation of the solar-wind proton spectrum in the cascade charge-exchange process in the extended hydrogen corona of Mars has been self-consistently modeled; and the energy fluxes and energy spectra of hydrogen atoms penetrating into the daytime upper atmosphere through the boundary of the induced magnetosphere have been determined. The obtained characteristics make it possible to model numerically the proton auroral phenomena observed in the upper atmosphere of Mars with the Imaging Ultraviolet Spectrometer onboard the Mars Atmosphere and Volatile Evolution spacecraft. In our future studies, we plan to compare the results of these calculations to those of observations, which will provide a unique opportunity to determine more accurately the properties of the atmosphere and the magnetic field of Mars, as well as will improve the techniques for determining the solar wind parameters.

Significant technology advances have enabled planetary exploration aircraft to be considered as a viable science platform. These systems fill in a unique planetary science measurement gap, that of the regional scale, near-surface observation while providing a new perspective for planetary discovery. Exploration of Mars using UAV (Unmanned Aerial Vehicle) has been planned for over 25 years by leading space organizations such as NASA. Recent efforts have been able to produce some mature mission and flight system concepts, ready for flight project implementation. There are however si0gnificant numbers of challenges associated with getting an airplane to fly through the thin, carbon dioxide-rich Martian atmosphere. Traditional aircraft design expertise does not always apply to this sort of vehicle, and geometric, aerodynamic, and mission restrictions result in a restricted viable design space. This paper presents the conceptual approach that was taken to design a UAV capable of performing a VTOL (Vertical Take-Off and Landing) in the atmosphere of Mars. The UAV was designed to participate in the International Planetary Aerial Systems Challenge 2021. The UAV could carry a science payload of up to 5 kg (weight on mars).

On July 30, 2020, the roar of an Atlas V rocket blasting off from Florida’s Cape Canaveral Air Force Station sounded the opening of a monumental quest, the Mars 2020 mission. Hidden within the shro...

Abstract— For the first time, the calculations of the penetration of protons of the undisturbed solar wind into the daytime atmosphere of Mars due to charge exchange in the extended hydrogen corona (Shematovich et al., 2021) are used allowing us to determine self-consistently the sources of suprathermal oxygen atoms, as well as their kinetics and transport. An additional source of hot oxygen atoms—collisions accompanied by the momentum and energy transfer from the flux of precipitating high-energy hydrogen atoms to atomic oxygen in the upper atmosphere of Mars—was included in the Boltzmann kinetic equation, which was solved with the Monte-Carlo kinetic model. As a result, the population of the hot oxygen corona of Mars has been estimated; and it has been shown that the proton aurorae are accompanied by the atmospheric loss of atomic oxygen, which is evaluated within a range of (3.5–5.8) × 107 cm–2 s–1. It has been shown that the exosphere becomes populated with a substantial amount of suprathermal oxygen atoms with kinetic energies up to the escape energy, 2 eV. The atomic oxygen loss rate caused by a sporadic source in the Martian atmosphere—the precipitation of energetic neutral atoms of hydrogen (H‑ENAs) during proton aurorae at Mars—was estimated by the self-consistent calculations according to a set of the Monte-Carlo kinetic models. These values turned out be comparable to the atomic oxygen loss supported by a regular source—the exothermic photochemical reactions (Groeller et al., 2014; Jakosky et al., 2018). It is currently supposed that the atmospheric loss of Mars due to the impact of the solar wind plasma and, in particular, the fluxes of precipitating high-energy protons and hydrogen atoms during solar flares and coronal mass ejections may play an important role in the loss of the neutral atmosphere on astronomic time scales (Jakosky et al., 2018).

Our understanding of the Martian atmosphere, terrain and subsurface has continuously evolved over the past couple of decades as a result of a number of successful orbiter and rover missions. This prompts a need to revisit the first holistic review of Martian geomorphology, based on images from the Viking orbiters, by Victor R. Baker in 1981. Several of the interpretations and recommendations based on remote sensing in Baker’s paper are as valid today as they were four decades ago. With an unprecedented focus on Mars exploration in the coming decades, it is important to revisit the advances and prospects in Martian geomorphology research.

Mars is the nearest planet that potentially harbors life and that can be explored by humans, so its history of water is of considerable importance. Water was abundant on early Mars but disappeared as Mars became the cold, dry planet we see today. Loss of water to space played a major role in the history of this water. Variability of components of the atmosphere that can drive escape has taken place on all timescales, from interannual to the 105-, 106-, and >107-year timescales of obliquity variations to the 4 billion-year timescale of large-scale climate evolution. These variations have had a major impact on the behavior of the atmosphere, climate, and water. They also make it difficult to evaluate quantitatively where the water has gone. Despite this uncertainty, the observed enrichment in the ratio of deuterium/hydrogen requires that loss to space has been substantial. ▪ Mars is the nearest planet that potentially harbors life and that can be explored by humans, so its history of water is important. ▪ The Mars atmosphere has varied on all timescales, from year to year to its 4 billion-year history, driving the evolution of water. ▪ Loss of water from the Martian atmosphere to space has been a major process in Mars’ atmospheric evolution.

The presence of dust in the Mars atmosphere can adversely affect heat shields of entry vehicles by enhancing erosion and increasing surface heat fluxes. However, the accuracy of numerical simulatio...

Mars lacks a substantial magnetic field; as a result, the solar wind ablates the Martian atmosphere, and cosmic rays from solar flares make the surface uninhabitable. Therefore, any terraforming attempt will require an artificial Martian magnetic shield. The fundamental challenge of building an artificial magnetosphere is to condense planetary-scale currents and magnetic fields down to the smallest mass possible. Superconducting electromagnets offer a way to do this. However, the underlying physics of superconductors and electromagnets limits this concentration. Based upon these fundamental limitations, we show that the amount of superconducting material is proportional to $B_{\rm c}^{-2}a^{-3}$, where Bc is the critical magnetic field for the superconductor and a is the loop radius of a solenoid. Since Bc is set by fundamental physics, the only truly adjustable parameter for the design is the loop radius; a larger loop radius minimizes the amount of superconducting material required. This non-intuitive result means that the ‘intuitive’ strategy of building a compact electromagnet and placing it between Mars and the Sun at the first Lagrange point is unfeasible. Considering reasonable limits on Bc, the smallest possible loop radius is ~10 km, and the magnetic shield would have a mass of ~ 1019 g. Most high-temperature superconductors are constructed of rare elements; given solar system abundances, building a superconductor with ~ 1019 g would require mining a solar system body with several times 1025 g; this is approximately 10% of Mars. We find that the most feasible design is to encircle Mars with a superconducting wire with a loop radius of ~3400 km. The resulting wire diameter can be as small as ~5 cm. With this design, the magnetic shield would have a mass of ~ 1012 g and would require mining ~ 1018 g, or only 0.1% of Olympus Mons.

This paper presents the results of calculating the efficiency of solar wind proton charge exchange as a function of variations in the column density of hydrogen atoms in the extended corona of Mars. The presence of regular density variations has been known for a long time and has been associated with the change of seasons on Mars. However, sporadic density variations in the upper Martian atmosphere were detected recently as well. They were caused by various processes in the underlying atmosphere, such as ejection of water vapor and ice particles at altitudes up to 100 km due to global dust storms, which was discovered in the Mars Express and MAVEN observations. Taking into account the variations in the column density with the observed amplitude up to one order of magnitude is absolutely necessary to correctly consider the interaction of solar wind protons with the Martian atmosphere. The calculations using the kinetic Monte Carlo model revealed that with a 2- and 5-fold increase in the column density of H atoms in the corona of Mars, the charge exchange efficiency also increases and reaches 6% and 8%, respectively, as compared to the base value of 4%. The energy spectrum of hydrogen atoms penetrating into the Martian atmosphere does not change and remains identical in structure to the spectrum of undisturbed solar wind protons. These estimates, combined with the previously developed kinetic model of the proton and hydrogen atom precipitation into the planetary atmosphere, make it possible to do the following: to trace all the stages of the penetration of the undisturbed solar wind protons into the dense layers of the atmosphere, as well as interpret the observed characteristics of proton auroras depending on the variations of atomic hydrogen content in the Martian corona.

When a planet has an orbiting moon, atoms and molecules that escape the planetary atmosphere as ions and are accelerated into space may be implanted and preserved inside the moon’s surface. Here, we determine the long-term averaged anisotropy of ions escaping the atmosphere of Mars and impacting its moon Phobos from more than four years of in situ ion observations. These measurements are used to quantify an estimate of the average flux of ions that has been impacting each location on Phobos over geologic timescales. We find that the flux of bombarding Martian ions is highly asymmetric on the moon’s surface, as the nearside of Phobos sees a flux higher by a factor of 15 to 100 than its farside. We show that a first consequence of this is that Martian atmospheric oxygen, carbon, nitrogen and argon atoms are implanted and may be preserved inside the uppermost hundreds of nanometres of Phobos’s nearside regolith grains, which may be brought back to Earth by future sample return missions. The second effect is that alteration of the regolith properties is asymmetric on Phobos’s surface, as Martian ions accelerate weathering of the nearside by a factor of ~2. Martian atmospheric atoms are implanted in and alter regolith grains on the nearside surface of Phobos, according to an analysis of observations of ion escape from Mars’s atmosphere.

The present study uses five Martian years of observations from Mars Climate Sounder onboard Mars Reconnaissance Orbiter for investigating the Aphelion Cloud Belt (ACB) over the tropics. Analysis of zonal mean water ice column opacity suggests that the spatial extension of the ACB is mainly confined over the tropics and mid-latitudes (-20 – 40°N) during LS ~ 45 – 135° (LS = 0° signifies northern spring equinox). The ACB is seen primarily in the nighttime only due to the truncation of the daytime profile observations at significantly higher altitudes (at ~30 km). Zonal mean ice extinction profiles show ACB’s altitudinal range within ~10 – 40 km, and the existence of a thin cloud band in the absence of a thick ACB during aphelion season. Three phases of the ACB could be identified as the formation phase during LS = 45 – 75° (phase 1), the peak phase during LS = 76 – 105° (phase 2), and the decaying phase during LS = 106 – 135° (phase 3). Observation of the cloud latitude belt shows a northward movement starting from phase 2, prominent over regions nearby Lunae Planum and Xanthe Terra. During this phase, the top level of thick clouds within the ACB decreases to ~20 km in the southern hemisphere, while it increases a little over the northern hemisphere (NH). The decreasing tendency continues in phase 3 over the entire region −10 – 10°N, and the thick cloud base moves higher over the NH, though the vertical depth of it becomes narrower than phase 2. Temperature profiles do not show any noticeable influence on the northward evolution of the ACB. However, the study at a regional level indicates a possible association of upper tropospheric dustiness with the ACB’s evolution. The mechanism is evident in the correlation analysis mostly at an altitude range of ~18 – 35 km. The migrating semidiurnal tide (SMD) as a proxy of dust or water ice forcing, and the calculated upper tropospheric dust radiative heating, shows an apparent northward movement of their peak amplitude within the three phases of the ACB. This match between the spatiotemporal variations of the SMD and the water ice was not observed previously. However, the correlating behavior seems to be prominent in the areas nearby Lunae Planum and Xanthe Terra and the upper-tropospheric region of the atmosphere.

To partially meet the communication requirements in Mars, low-frequency ground-to-ground communication is likely to be used in the future and hence, it is desirable to increase electron density in the Martian ionosphere. As a convenient means to this, we have proposed and explored the production of high electron density regions in the Martian atmosphere in daytime by suspension of low work function dust, specifically Cs-coated bronze in the atmosphere. Equations of the kinetics of the dusty air in sunlight have been introduced and a numerical estimate of the daytime electron density at 60–100 km heights has been obtained as a function of the dust parameters. Photoelectric emission from dust and accretion of electrons and ions on dust particles play the key role in getting the desired electron density at high altitudes (60–100 km). A discussion of the numerical results has been given with conclusions.

Airborne dust is an important constituent in the Martian atmosphere because of its radiative interaction with the atmospheric circulation, and dust size is one crucial factor in determining this effect. In numerical modeling of the dust processes, description of the dust size is usually dependent on the choice of a particular size distribution function, or with fixed values of effective radius (ER) and effective variance (EV) though they are variable in reality. In this work, analytical expressions have been derived to specify ER and EV for N-bin dust schemes based on the model calculated dust mixing ratio. Numerical simulations based on this approach thus consider the effects of variable ER on the atmospheric radiation and their interaction. The results have revealed some interesting features of the dust distribution parameters such as the seasonal and spatial variation of ER and EV, which are generally consistent with some previous observational and modeling studies. Compared with the usual approach of using fixed ER, simulation results with the present approach suggest that the variability of ER can have significant effect on the simulated thermal field of the Martian atmosphere., Comment: 15 pages, 4 figures

The article presents the calculation technique and the results of a study of the penetration of hot gas from the shock layer into the internal space of the prospective descent module due to leakage of the structure of the vehicle during descent in the Martian atmosphere.

The past Martian atmosphere is often compared to the Archean Earth’s as both were dominated by CO2-rich and O2-poor chemistries. Archean Earth rocks preserve mass-independently fractionated sulfur isotopes (S-MIF; non-zero Δ33S and Δ36S), originating from photochemistry in an anoxic atmosphere. Thus, Martian crustal rocks might also be expected to preserve a S-MIF signature, providing insights into past atmospheric chemistry. We have used secondary ion mass spectrometry (SIMS) to investigate in situ, the sulfur isotope systematics of NWA 8171 (paired to NWA 7034), a Martian polymict breccia containing pyrite that formed through hydrothermal sulfur addition in a near-surface regolith setting. In this meteorite, pyrite grains have a weighted mean of Δ33S of -0.14 ± 0.08 ‰ and Δ36S = -0.70 ± 0.40 ‰ (2 s.e.m.), so the S-MIF signature is subtle. Sulfur isotope data for four additional shergottites yield Δ33S values that are not resolvable from zero, as in previous studies of shergottites. At first glance the result for the polymict breccia might seem surprising, but no Martian meteorite yet has yielded a S-MIF signature akin to the large deviations seen on Earth. We suggest that S-MIF-bearing aerosols (H2SO4 and S8) were produced when volcanic activity pushed a typically oxidising Martian atmosphere into a reduced state. After rain-out of these aerosols, S8 would tend to be oxidised by chlorate, dampening the S-MIF signal, which might be somewhat retained in the more abundant photolytic sulfate. Then in the regolith, mixing of aqueous surface-derived sulfate with igneous sulfide (the latter with zero MIF), to form the abundant pyrite seen in NWA 8171, would further dampen the S-MIF signal. Nonetheless, the small negative Δ33S anomalies seen in Martian meteorites imply that volcanic activity was sufficient to produce a reducing atmosphere at times. This volcanically-driven atmospheric evolution would tend to produce high levels of carbonyl sulfide (OCS). Given that OCS is a relatively long-lived strong greenhouse gas, the S-MIF signal implies that volcanism periodically generated warmer conditions, perhaps offering an evidence-based solution to the young wet Mars paradox.

Model calculations of the charge exchange efficiency for solar wind protons colliding with hydrogen atoms of the extensive Martian corona are presented. It is shown that the energy spectrum of hydrogen atoms penetrating in the Martian atmosphere is identical to the spectrum of protons of the unperturbed solar wind. The charge exchange efficiency varies from 2 to 4% depending on the boundary location of the Martian induced magnetosphere. The presented calculations, combined with the kinetic model of proton precipitation proposed earlier, enable us to follow all proton penetration stages of the unperturbed solar wind into denser atmospheric layers and to estimate the characteristics of proton aurorae observed on the Mars.

Photon buildup is a function of energy, medium, and geometry and therefore must be specifically calculated for the case of interest. The Martian atmosphere, mostly comprising carbon dioxide, is bec...

We present the model calculation results of the atomic oxygen loss rate from the Martian atmosphere induced by precipitation of high-energy protons and hydrogen atoms (H/H+) from the solar wind plasma. Penetration of energetic protons and hydrogen atoms from the solar wind plasma to the upper atmosphere of Mars at altitudes of 100−250 km is accompanied by the momentum and energy transfer in collisions with the main component, atomic oxygen. This process is considered as atmospheric gas sputtering during proton auroral events, which is accompanied by formation of the suprathermal hydrogen and oxygen atom fluxes escaping from the atmosphere. When calculating the formation rate of suprathermal atoms, the modified Monto Carlo kinetic model was used. This model was earlier developed to analyze the data of the Analyzer of Space Plasma and Energetic Atoms (ASPERA-3) and the Solar Wind Ion Analyzer (SWIA) onboard the Mars Express (MEX) and the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, respectively. We study the processes of kinetics and transport of hot oxygen atoms in the transition zone (from the thermosphere to the exosphere) of Mars’ upper atmosphere. The kinetic energy distribution functions for suprathermal oxygen atoms were calculated. It has been shown that, during proton auroral events on Mars, the exosphere is populated with a significant number of suprathermal oxygen atoms, the kinetic energy of which reaches the escape energy, 2 eV. In addition to photochemical sources, a hot fraction is formed in the oxygen corona; and a nonthermal flux of atomic oxygen escaping from the Martian atmosphere is produced during proton aurora events. Proton aurorae are sporadic auroral events. Consequently, according to the estimates obtained from the recent MAVEN observations the magnitude of the precipitation-induced escaping flux of hot oxygen atoms may become prevailing over the photochemical sources under conditions of the extreme solar events such as solar flares and coronal mass ejections.

Induced magnetospheres form around conductive non-magnetized planetary objects (such as the ionospheres of Mars, Venus, Titan, Pluto and comets) in the electrodynamic interaction with a magnetized flowing plasma, such as the solar wind. The resulting induced currents couple the ionosphere and the deflected plasma, thus they provide insight into the solar wind’s role in powering the heating, escape and evolution of planetary atmospheres. In contrast to the analogous current systems in intrinsic magnetospheres, which were mapped decades ago at Earth, the current systems of induced magnetospheres are largely unexplored. Here, we use five years of magnetic field measurements from the Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter to empirically map the current systems of the Martian induced magnetosphere. We find unexpected features, in particular: coupling of the ionosphere and the bow shock, asymmetries between the north–south electric hemispheres and a twist in the near-Mars current system. The current flow pattern in the induced magnetosphere of Mars indicates a system driven by a magnetospheric convective electric field, powered by the solar wind interaction. Without an intrinsic magnetic field, Mars’s magnetosphere is induced by direct interaction between its atmosphere and the solar wind. The mapping of the associated current system, obtained by the MAVEN spacecraft, unveils its convective-driven nature and displays various structural differences compared to Earth.

The paper presents a numerical analysis of aerophysical nonequilibrium processes occurring near the surface of the Schiaparelli entry vehicle in the region of hypersonic flight in the dense Martian atmosphere. The two-dimensional model realized is based on the system of self-consistent equations of nonequilibrium physical and chemical mechanics of a partially ionized, multicomponent, viscous, and heat-conducting gas. A numerical investigation of the conditions of the flow around the Schiaparelli entry vehicle during its landing onto the Mars surface shows that in the altitude range from 80 to 30 km the electron concentration in the flow region disturbed by the entry vehicle amounts to 109 to 1011 cm–3. These calculated data are confirmed by the flight data concerning the blocking of radio signals transmitted by the entry vehicle to the orbital module.

The abundance and distribution of water within Mars through time plays a fundamental role in constraining its geological evolution and habitability. The isotopic composition of martian hydrogen provides insights into the interplay between different water reservoirs on Mars. However, D/H (deuterium/hydrogen) ratios of martian rocks and of the martian atmosphere span a wide range of values. This has complicated identification of distinct water reservoirs in and on Mars within the confines of existing models that assume an isotopically homogenous mantle. Here we present D/H data collected by secondary ion mass spectrometry for two martian meteorites. These data indicate that the martian crust has been characterized by a constant D/H ratio over the last 3.9 billion years. The crust represents a reservoir with a D/H ratio that is intermediate between at least two isotopically distinct primordial water reservoirs within the martian mantle, sampled by partial melts from geochemically depleted and enriched mantle sources. From mixing calculations, we find that a subset of depleted martian basalts are consistent with isotopically light hydrogen (low D/H) in their mantle source, whereas enriched shergottites sampled a mantle source containing heavy hydrogen (high D/H). We propose that the martian mantle is chemically heterogeneous with multiple water reservoirs, indicating poor mixing within the mantle after accretion, differentiation, and its subsequent thermochemical evolution.

The Mars Environmental Dynamics Analyzer will be dedicated to getting meteorological data from Mars during NASA’s Mars 2020 rover mission. High-quality Mars atmosphere measurements are required in ...

The present knowledge of the Mars atmosphere is greatly limited by a lack of global measurements of winds and aerosols. Hence, measurements of height-resolved wind and aerosol profiles are a priority for new Mars orbiting missions. We have designed a direct-detection lidar (MARLI) to provide global measurements of dust, winds and water ice profiles from Mars orbit. From a 400-km polar orbit, the instrument is designed to provide wind and backscatter measurements with a vertical resolution of 2 km and with resolution of 2° in latitude along track. The instrument uses a single-frequency, seeded Nd:YAG laser that emits 4 mJ pulses at 1064 nm at a 250 Hz pulse rate. The receiver utilizes a 50-cm diameter telescope and a double-edge Fabry-Pérot etalon as a frequency discriminator to measure the Doppler shift of the aerosol-backscatter profiles. The receiver also includes a polarization-sensitive channel to detect the cross-polarized backscatter profiles from water ice. The receiver uses a sensitive 4 × 4 pixel HgCdTe avalanche photodiode array as a detector for all signals. Here we describe the measurement concept, instrument design, and calculate its performance for several cases of Mars atmospheric conditions. The calculations show that under a range of atmospheric conditions MARLI is capable of measuring wind speed profiles with random error of 2–4 m/s within the first three scale heights, enabling vertically resolved mapping of transport processes in this important region of the atmosphere.

Understanding and predicting processes that perturb planetary ionospheres is of paramount importance for long-distance radio communication. Perhaps the oldest known ionospheric disturbances are ‘sporadic E layers’1: unpredictable and short-lived concentrations of plasma2, which can bounce radio signals over the horizon for thousands of kilometres3. Consequentially, local radio broadcasts can become jammed by more distant transmissions, and thus sporadic E layers are a potentially serious complication for commercial radio, aviation, shipping or the military. According to the current theory of their formation, we should also expect an equal proportion of localized ionospheric density depletions to develop. However, no such ‘sporadic E rifts’ have been detected in over 85 years of ionospheric research. In addition, despite being common at Earth, no sporadic E layers have yet been reported at other planets. Here we report the detection of sporadic E-like phenomena in the ionosphere of Mars by NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft, providing a physical explanation for previous unexplained observations at Mars4–7. We observe enhanced-density layers that can be explained through the presence of a sporadic E-like mechanism, and we establish the existence of sporadic E rifts in nature. We find that, unlike the case at Earth, Martian sporadic E features are trapped in a near-perpetual state of dynamic formation and may form at predictable locations. Also unlike the case at Earth, Martian sporadic E features are readily accessible to satellites, and indeed MAVEN has already encountered more of the phenomena at Mars than have ever been explored in situ at Earth with suborbital rockets. Sporadic E layers are unpredictable terrestrial ionospheric phenomena that can perturb telecommunication. Plasma features akin to sporadic E layers and their opposite (sporadic E rifts), never observed on Earth, were detected in the ionosphere of Mars from MAVEN data. In contrast to those observed on Earth, they are long lived and form at predictable locations.

The photoelectron peak at 22–27 eV, a distinctive feature of the energetic electron distribution in the dayside Martian ionosphere, is a useful diagnostic of solar extreme ultraviolet (EUV) and X-ray ionization as well as of large-scale transport along magnetic field lines. In this work, we analyze the pitch angle distribution (PAD) of energetic electrons at 22–27 eV measured during several representative Mars Atmosphere and Volatile Evolution (MAVEN) orbits, based on the electron spectra gathered by MAVEN’s Solar Wind Electron Analyzer (SWEA) instrument. On the dayside, most photoelectron spectra show an isotropic PAD as is expected from production via solar EUV/X-ray ionization. The photoelectron spectra occasionally observed on the nightside show instead a strongly anisotropic PAD, indicative of cross-terminator transport along ambient magnetic field lines. This would in turn predict the presence of dayside photoelectrons, also with a strongly anisotropic PAD, which was indeed revealed in SWEA data. Comparison with magnetic field measurements made by the MAVEN Magnetometer suggests that on average the photoelectrons with anisotropic PAD stream away from Mars on the dayside and towards Mars on the nightside, further supporting the scenario of day-to-night transport. On both sides, anisotropic photoelectrons tend to be observed above the photoelectron exobase at ~160 km where photoelectron transport dominates over local production and energy degradation.

Doubly charged positive ions (dications) are an important component of planetary ionospheres because of the large energy required for their formation. Observations of these ions are exceptionally difficult due to their low abundances; until now, only atomic dications have been detected. The Neutral Gas and Ion Mass Spectrometer (NGIMS) measurements made on board the recent Mars Atmosphere and Volatile Evolution mission provide the first opportunity for decisive detection of molecular dications, CO2++ in this case, in a planetary upper atmosphere. The NGIMS data reveal a dayside averaged CO2++ distribution declining steadily from 5.6 cm−3 at 160 km to below 1 cm−3 above 200 km. The dominant CO2++ production mechanisms are double photoionization of CO2 below 190 km and single photoionization of CO2+ at higher altitudes; CO2++ destruction is dominated by natural dissociation, but reactions with atmospheric CO2 and O become important below 160 km. Simplified photochemical model calculations are carried out and reasonably reproduce the data at low altitudes within a factor of 2 but underestimate the data at high altitudes by a factor of 4. Finally, we report a much stronger solar control of the CO2++ density than of the CO2+ density .

Electron pitch angle distributions similar to bidirectional electron conics (BECs) have been reported at Mars in previous studies based on analyses of Mars Global Surveyor measurements. BEC distribution, also termed “butterfly” distribution, presents a local minimum flux at 90° and a maximum flux before reaching the local loss cone. Previous studies have focused on 115 eV electrons that were produced mainly via solar wind electron impact ionization. Here using Solar Wind Electron Analyzer measurements made onboard the Mars Atmosphere and Volatile Evolution spacecraft, we identify 513 BEC events for 19–55 eV photoelectrons that were generated via photoionization only. Therefore, we are investigating electrons observed in regions well away from their source regions, to be distinguished from 115 eV electrons observed and produced in the same regions. We investigate the spatial distribution of the 19–55 eV BECs, revealing that they are more likely observed on the nightside as well as near strong crustal magnetic anomalies. We propose that the 19–55 eV photoelectron BECs are formed due to day-to-night transport and the magnetic mirror effect of photoelectrons moving along cross-terminator closed magnetic field lines.

O++ is an interesting species in the ionospheres of both the Earth and Venus. Recent measurements made by the Neutral Gas and Ion Mass Spectrometer (NGIMS) on board the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft provide the first firm detection of O++ in the Martian ionosphere. This study is devoted to an evaluation of the dominant O++ production and destruction channels in the dayside Martian ionosphere, by virtue of NGIMS data accumulated over a large number of MAVEN orbits. Our analysis reveals the dominant production channels to be double photoionization of O at low altitudes and photoionization of O+ at high altitudes, respectively, in response to the varying degree of O ionization. O++ destruction is shown to occur mainly via charge exchange with CO2 at low altitudes and with O at high altitudes. In the dayside median sense, an exact balance between O++ production and destruction is suggested by the data below 200 km. The apparent discrepancy from local photochemical equilibrium at higher altitudes is interpreted as a signature of strong O++ escape on Mars, characterized by an escape rate of 6×1022 s–1.

The Martian hydrogen exosphere extends out of the bow shock, forming a "hydrogen corona". The solar wind interacts directly with the hydrogen corona. During an ICME event on 7 March 2015, the SWIA instrument onboard Mars Atmosphere and Volatile Evolution mission (MAVEN) observed that the pick-up H+ fluxes in upstream solar wind were enhanced. Also increased were the penetrating H+ fluxes in the Martian atmosphere. Quantitatively, these penetrating H+ fluxes cannot increase by a factor of 5 simply due to a factor of 3 increase in the solar wind density, suggesting that the increased abundance of exospheric hydrogen upstream of the bow shock was a consequence of the passage of the ICME. A denser outer hydrogen corona at high altitudes suggests that the expansion of the neutral atmosphere was caused by the ICME. The excited and heated hydrogen exosphere probably indicates an elevated hydrogen escape rate during an ICME.

The exobase is defined as the interface between the strongly collisional and the collisionless parts of an atmosphere. Although in reality the exobase is a transition region of finite depth, it is conventionally defined as the boundary above which an upwardly ejected neutral particle makes one collision at higher altitudes. Such an idealized definition is of practical use and serves as a good tracer of the overall size of an atmosphere as it expands and contracts under the influences of both external and internal sources. Knowledge of the atmospheric properties near the exobase is crucial to first-order estimates of atmospheric escape rates on terrestrial planets. Since its arrival at Mars on 21 September 2014, the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft has provided comprehensive maps of the Martian upper atmosphere under a variety of conditions. This allows, for the first time, a thorough investigation of the variations of the exobase altitude on this red planet. In this study, we use the N2 density measurements accumulated by MAVEN’s Neutral Gas and Ion Mass Spectrometer from October 2014 to November 2018 to determine the exobase altitudes for a large number of MAVEN orbits. Our analysis reveals clearly the variations of exobase altitude with local time and solar extreme ultraviolet (EUV) flux, as well as tentative evidence for the impact of global dust storms. These observations are indicative of thermal expansion of the Martian upper atmosphere, driven either externally by solar EUV energy deposition or internally by global dust storms.

An important population of the dayside Martian ionosphere are photoelectrons that are produced by solar Extreme Ultraviolet and X-ray ionization of atmospheric neutrals. A typical photoelectron energy spectrum is characterized by a distinctive peak near 27 eV related to the strong solar HeII emission line at 30.4 nm, and an additional peak near 500 eV related to O Auger ionization. In this study, the extensive measurements made by the Solar Wind Electron Analyzer on board the recent Mars Atmosphere and Volatile Evolution spacecraft are analyzed and found to verify the scenario that Martian ionosphere photoelectrons are driven by solar radiation. We report that the photoelectron intensities at the centers of both peaks increase steadily with increasing solar ionizing flux below 90 nm and that the observed solar cycle variation is substantially more prominent near the O Auger peak than near the HeII peak. The latter observation is clearly driven by a larger variability in solar irradiance at shorter wavelengths. When the solar ionizing flux increases from 1 mW·m-2 to 2.5 mW·m-2, the photoelectron intensity increases by a factor of 3.2 at the HeII peak and by a much larger factor of 10.5 at the O Auger peak, both within the optically thin regions of the Martian atmosphere.

The possibility of excitation of oscillations in a Schumann resonator in the atmosphere of Mars is discussed. On Earth, the main source of energy in the resonator cavity are thunderstorms at tropical latitudes. On Mars, electric phenomena are possible during dust events such as dust columns and dust storms. The charging of dust grains in a dust column on the surface of Mars is considered and the possible values of the electric fields generated by the column are determined. Estimates of the amplitude of oscillations in a Schumann resonator on Mars are obtained and compared with the amplitudes of oscillations in a Schumann resonator on Earth.

Unlike Earth, Mars lacks a global dipolar magnetic field but is dominated by patches of a remnant crustal magnetic field. In 2021, the Chinese Mars Rover will land on the surface of Mars and measure the surface magnetic field along a moving path within the possible landing region of 20°W–50°W, 20°N–30°N. One scientific target of the Rover is to monitor the variation in surface remnant magnetic fields and reveal the source of the ionospheric current. An accurate local crustal field model is thus considered necessary as a field reference. Here we establish a local crust field model for the candidate landing site based on the joint magnetic field data set from Mars Global Explorer (MGS) and Mars Atmosphere and Volatile Evolution (MAVEN) data combined. The model is composed of 1,296 dipoles, which are set on three layers but at different buried depths. The application of the dipole model to the joint data set allowed us to calculate the optimal parameters of their dipoles. The calculated results demonstrate that our model has less fitting error than two other state-of-the art global crustal field models, which would indicate a more reasonable assessment of the surface crustal field from our model.

Solar energy is the primary driving force behind a planet’s climate system, and surface albedo plays a key role in determining the energy budget of the planet. Coupling the Snow, Ice, and Aerosol Radiation (SNICAR) with the Laboratoire de Meteorologie Dynamique (LMD) Mars General Circulation Model (MGCM) to create a new coupled model leads to an approximately 4% drop in the net CO2 ice deposition on Mars. Newly simulated surface albedo affects the concentration of gaseous species in the Martian atmosphere (condensation-sublimation cycle). The new set-up also impacts the solar energy available in the atmosphere. These two effects together lead to subsequent and significant changes in other chemical species in the Martian atmosphere. Compared with results of the MGCM model alone, in the new coupled model CO2 (gas) and O3 show a drop of about 1.17% and 8.59% in their respective concentrations, while H2O (vapor) and CO show an increase of about 13.63% and 0.56% in their respective concentrations. Among trace species, OH shows a maximum increase of about 29.44%, while the maximum drop of 11.5% is observed in the O concentration. Photochemically neutral species such as Ar and N2 remain unaffected by the albedo changes.

The \begin{document}$ {\rm{CO}}_2^+$\end{document} ultraviolet doublet (UVD) emission near 289 nm is an important feature of dayside airglow emission from planetary upper atmospheres. In this study, we analyzed the brightness profiles of \begin{document}$ {\rm{CO}}_2^+$\end{document} UVD emission on Mars by using the extensive observations made by the Imaging Ultraviolet Spectrograph on board the recent Mars Atmosphere and Volatile Evolution spacecraft. Strong solar cycle and solar zenith angle variations in peak emission intensity and altitude were revealed by the data: (1) Both the peak intensity and altitude increase with increasing solar activity, and (2) the peak intensity decreases, whereas the peak altitude increases, with increasing solar zenith angle. These observations can be favorably interpreted by the solar-driven scenario combined with the fact that photoionization and photoelectron impact ionization are the two most important processes responsible for the production of excited-state \begin{document}$ {\rm{CO}}_2^+$\end{document} and consequently the intensity of \begin{document}$ {\rm{CO}}_2^+$\end{document} UVD emission. Despite this, we propose that an extra driver, presumably related to the complicated variation in the background atmosphere, such as the occurrence of global dust storms, is required to fully interpret the observations. In general, our analysis suggests that the \begin{document}$ {\rm{CO}}_2^+$\end{document} UVD emission is a useful diagnostic of the variability of the dayside Martian atmosphere under the influences of both internal and external drivers.

In recent studies of the Martian atmosphere, strong diurnal variation in the dust was discovered in the southern hemisphere during major dust storms, which provides strong evidence that the commonly recognized meridional transport process is driven by thermal tides. This process, when coupled with deep convection, could be an important part of the short-term atmospheric dynamics of water escape. However, the potential of this process to alter the horizontal distribution of moist air has not been systematically investigated. In this work, we conducted pre-research on the horizontal transport of water vapor associated with the migrating diurnal tide (DW1) at 50 Pa in the upper troposphere during major dust storms based on the Mars Climate Database (MCD) 5.3, a state-of-the-art database for Martian atmospheric research that has been validated as simulating the relevant short-period atmospheric dynamics well. We found westward-propagating diurnal patterns in the global water vapor front during nearly all the major dust storms from Martian years (MYs) 24 to 32. Statistical and correlation analyses showed that the diurnal transport of water vapor during global and A-season regional dust storms is dominated by the DW1. The effect of the tidal transport of water vapor varies with the types of dust storms in different seasons. During regional dust storms, the tidal transport induces only limited diurnal motion of the water vapor. However, the horizontal tidal wind tends to increase the abundance of daytime water vapor at mid- to low latitudes during the MY 28 southern summer global dust storm while decreasing it during the MY 25 southern spring global dust storm. The tidal transport process during these two global dust storms can induce opposite effects on water escape.

Proton cyclotron waves (PCWs) can be generated by ion pickup of Martian exospheric particles in the solar wind. The solar wind ion pickup process is highly dependent on the “IMF cone angle” — the angle between the solar wind velocity and the interplanetary magnetic field (IMF), which also plays an important role in the generation of PCWs. Using data from 2.15 Martian years of magnetic field measurements collected by the Mars Atmosphere and Volatile Evolution (MAVEN) mission, we have identified 3307 upstream PCW events. Their event number distribution decreases exponentially with their duration. A statistical investigation of the effects of IMF cone angle on the amplitudes and occurrence rates of PCWs reveals a slight tendency of PCWs’ amplitudes to decrease with increasing IMF cone angle. The relationship between the amplitude and IMF cone angle is weak, with a correlation coefficient r = –0.3. We also investigated the influence of IMF cone angle on the occurrence rate of PCWs and found that their occurrence rate is particularly high for intermediate IMF cone angles (~18°–42°) even though highly oblique IMF orientation occurs most frequently in the upstream region of the Martian bow shock. We also conclude that these variabilities are not artefacts of temporal coverage biases in MAVEN sampling. Our results demonstrate that whereas IMF cone angle strongly influences the occurrence of PCWs, IMF cone angle may also weakly modulate their amplitudes in the upstream region of Mars.

X-ray communication (XCOM) is an advanced space-communication technology. The high penetration of X-ray enables XCOM to achieve lower signal attenuation than conventional optical communication in Martian dust storm. This study provided a demonstration of this approach based on simulation methods. The transmission properties of X-ray beams in Martian non-dust storm weather were evaluated based on the MCNP5 code. Results demonstrated that the X-ray beam can transmit through a long-distance in Martian atmosphere. Moreover, on the basis of the anomalous diffraction and Mie theory codes, the transmission properties of X-ray and optical links in Martian dust storm were evaluated. Results showed that the dust attenuation of the X-ray links were significantly lower than that of optical links. Moreover, the penetration and communication performance of X-ray links were evaluated and compared with the optical link, considering atmospheric and dust attenuation. Results indicated that XCOM can be used to establish a low-BER communication link between rovers, and from the rover to the orbiter, in Martian dust storm.

We perform a statistical analysis of data from the Mars Atmosphere and Volatile Evolution (MAVEN) project on the global distribution of protons in the Martian magnetosheath. Our results show that the proton number density distribution has a south-north asymmetry. This south-north asymmetry is most likely caused by the south-north asymmetric distributions of the crustal magnetic fields at Mars. The strong crustal magnetic fields push the inner boundary of magnetosheath to a higher altitude in the southern hemisphere. Due to the outward movement of the inner boundary of the magnetosheath, a compressed magnetosheath forms, causing subsequent increases in proton number density, thermal pressure, and total pressure. Eventually, a balance is reached between the increased total pressure inside the magnetosheath and the increased magnetic pressure inside the induced magnetosphere. Our statistical study suggests that the Martian crustal magnetic fields can strongly affect the proton number density distribution in the Martian magnetosheath.

Using Mars Atmosphere and Volatile EvolutioN (MAVEN) observations from 2014 to 2019, we characterize how the structure and composition of the nightside ionosphere varies on solar cycle and seasonal timescales. At fixed altitudes between 150 and 200 km, plasma densities vary substantially on these timescales in response to variations in fixed thermospheric pressure levels, which cause the ionosphere to rise and fall in altitude. Additionally, solar cycle and seasonal trends in the electron impact ionization (EII) rate affects nightside densities; higher densities are observed near solar maximum and Mars perihelion (when EII rates are largest), and lower densities are observed near solar minimum and Mars aphelion (when EII rates are smallest). Lastly, densities in the high-altitude ( > 200 km) nightside ionosphere vary significantly over the solar cycle: topside O + densities vary by a factor of ∼ 50 and topside O 2 + densities vary by a factor of ∼ 40. Topside ion densities were relatively stable throughout the solar minimum of 2018–2019.