Mars Exploration Missions Research Articles

Interplanetary Coronal Mass Ejections and Stream Interaction Regions Observed by Tianwen-1 and MAVEN at Mars

The Tianwen-1 spacecraft is China's first Mars exploration mission. The Mars Orbiter Magnetometer (MOMAG) is a scientific instrument on board the Tianwen-1 mission that is designed to study magnetic fields at Mars, including the solar wind to the magnetosheath and the ionosphere. Using the first Tianwen-1/MOMAG data that is publicly available, we present an interplanetary coronal mass ejection (ICME) and stream interaction region (SIR) list based on in situ observations at Mars between 2021 November 16 and 2021 December 31. We compared the magnetic field intensity and vector magnetic field measurements from Tianwen-1/MOMAG and Mars Atmospheric Volatile EvolutioN (MAVEN)/Magnetometer (MAG) during the ICME and SIR interval and found a generally good consistency between them. Due to MAVEN's orbital adjustment since 2019, the Tianwen-1/MOMAG instrument is almost unique in its status as an interplanetary magnetic field monitor currently at Mars. The observations indicate that the MOMAG instrument on Tianwen-1 is performing well and can provide accurate measurements of the vector magnetic field in the near-Mars solar wind space. The multipoint observations combining MOMAG, MINPA, and MEPA on board Tianwen-1 with MAG, SWIA, and STATIC on board MAVEN will help develop systematic studies of the characteristics of ICMEs and SIRs at Mars, and their influences on the Martian atmosphere and ionosphere.

Tires for Mars Rovers: Reinforcing BR and BR/Vinyl-Methyl Silicone Rubber Compounds with Carbon Black, Nano-CaCO3, or Silica for Good Low-Temperature Dynamic-Mechanical Performance

ABSTRACT Dynamic increment in Mars exploration missions necessitates the development of new materials that can satisfy the ever more stringent requirements. Currently, most of the materials used for manufacturing Mars rovers and landers are based on various metal alloys that provide high reliability in the Martian environment. However, the future planned missions, including the first human crew landing on Mars, require the development of new rubber materials that could be used for sealing Mars suits, for tires/tracks, and for damping systems for heavy Mars rovers. This research aims to investigate the properties of butadiene rubber (BR) and butadiene/vinyl-methyl silicone rubber blends (BR/VMQ) filled with various reinforcing fillers: carbon blacks (CBs), silicas, and nanometric calcium carbonate (nano-CaCO3), in order to evaluate their performance from the point of view of Mars' environmental applications. The study revealed that the designed composites exhibit very good low-temperature elasticity, and the addition of 30 phr of high surface area CB (N220) or silica (Ultrasil 9100) results in good mechanical properties of the compounds. The mechanical properties of the BR/VMQ blends depend on the type of reinforcing filler. The addition of the CBs resulted in better mechanical properties, while the incorporation of silicas worsens the mechanical properties of BR/VMQ blends in comparison to their BR counterparts. The high-cis BR grade exhibits a strong tendency to crystallize in the operating temperature range on Mars (crystallization ∼−60 °C, melting ∼−20 °C), and the addition of the fillers nucleates the crystallization, resulting in a higher amount of the crystalline phase. This might be a serious problem for any sealing application of the rubber compounds. For this reason, a non-crystallizable BR grade is recommended for further studies.

Where No Surgeon Has Gone Before

Long-duration manned space missions beyond Low Earth Orbit, such as the new programs for the International Space Station around the Moon and the future Mars exploration missions, present a unique set of challenges to the health and well-being of crew members. Due to the inherent risks and the remote nature of these missions, we appreciate it is crucial to have at least one dedicated medical professional, specifically a surgeon astronaut, as part of the crew.

TeCVP: A Time-Efficient Control Method for a Hexapod Wheel-Legged Robot Based on Velocity Planning.

Addressing the problem that control methods of wheel-legged robots for future Mars exploration missions are too complex, a time-efficient control method based on velocity planning for a hexapod wheel-legged robot is proposed in this paper, which is named time-efficient control based on velocity planning (TeCVP). When the foot end or wheel at knee comes into contact with the ground, the desired velocity of the foot end or knee is transformed according to the velocity transformation of the rigid body from the desired velocity of the torso which is obtained by the deviation of torso position and posture. Furthermore, the torques of joints can be obtained by impedance control. When suspended, the leg is regarded as a system consisting of a virtual spring and a virtual damper to realize control of legs in the swing phase. In addition, leg sequences of switching motion between wheeled configuration and legged configuration are planned. According to a complexity analysis, velocity planning control has lower time complexity and less times of multiplication and addition compared with virtual model control. In addition, simulations show that velocity planning control can realize stable periodic gait motion, wheel-leg switching motion and wheeled motion and the operation time of velocity planning control is about 33.89% less than that of virtual model control, which promises a great prospect for velocity planning control in future planetary exploration missions.

Constraining the thermal inertia of Mars utilizing machine learning techniques

ABSTRACT Machine learning techniques, showing high automation and efficiency in handling large amounts of observation data, have been applied to predict the thermal inertia of Mars from surface kinetic temperatures. We created a large data set from well-established thermal models. Using this data set, we trained random forest (RF) models using surface kinetic temperatures, time of day, and other five accessible parameters as inputs to the model. The model performances for different local times were analysed and the characteristics of derived thermal inertia in typical regions on Mars were discussed. It is found that it is feasible and reliable to predict the thermal inertia of Mars using the well-trained RF. The RF predictions reflect the thermal signatures of Mars and show good agreement with previous retrievals. When using the nighttime data to make predictions, the RF model shows the best performance compared with those at other times of day. We also classified thermal inertia into four units: low, intermediate, relatively large, and large thermal inertia, and the RF model works for all four units. The predictive ability of the RF is also demonstrated for five representative regions on Mars, where the RF predictions are in good agreement with the bolometric nighttime thermal inertia from the thermal emission spectrometer. More importantly, the RF model provides a rapid retrieval of thermal inertia and speeds up the thermal analysis in upcoming Mars exploration missions with substantial data.

A Target-Based Non-Uniformity Self-Correction Method for Infrared Push-Broom Hyperspectral Sensors

Non-uniformity in the response of spectral image elements is an inevitable phenomenon in hyperspectral imaging, which mainly manifests itself as the presence of band noise in the acquired hyperspectral data. This problem is prominent in the infrared band owing to the detector material, operating environment, and other factors. Non-uniformity is an important factor that can affect the quality of the hyperspectral data, which has a serious impact on both data analysis and applications and requires corrections via technical means wherever possible. This paper proposes a novel target-based non-uniformity self-correction method for infrared push-broom hyperspectral images. The Mars Mineralogical Spectrometer (MMS) onboard the Tianwen-1 orbiter was used as the research and application object. The model is constructed and applied to the target scene characteristics and detection patterns of Mars remote sensing exploration, which are combined with the causes of noise generation in the infrared spectral image bands. The design of the MMS dual-channel Visible-Near-Infrared (V-NIR) and Near-Mid-Infrared (N-MIR) co-field of view co-target detection and laboratory calibration data for the V-NIR spectral band can achieve non-uniformity corrections (NUCs). Therefore, for the MMS in-orbit Mars exploration mission, the method selected spectral data (920–1055 nm) characterized by a reduced atmospheric influence to iteratively obtain the homogeneous region, which was used to calculate the non-uniformity correction factor for the N-MIR spectral band. This method was compared, validated, and evaluated with other conventional methods using both laboratory and in-orbit hyperspectral data. The results showed that the experimental data corrections were comparable to laboratory calibrations, with a maximum relative deviation of <2.6%. These results prove that our method not only provides an excellent non-uniformity correction, but also ensures spectral fidelity. It can thus be used as a non-uniformity correction process for the MMS and similar hyperspectral imagers.

Geotechnical assessment of terrain strength properties on Mars using the Perseverance rover’s abrading bit

An instrument for measuring the geotechnical properties of the Martian soil provides high-value science opportunities and high-priority mission-support capabilities that serve reconnaissance, science, and engineering. Such instrument can be used to characterize the terrain for drilling, landing, trafficability, and other surface operations. However, to date, instruments for measuring geotechnical properties have been absent from Mars exploration missions. This paper examines the use of the Mars 2020 Perseverance rover’s abrading bit tool to perform regolith strength measurements. The Perseverance rover’s abrading bit has a similar form factor to a Bevameter, a tool commonly used to collect engineering geotechnical data to assess terrain traversability. To demonstrate a methodology by which the abrading bit can be employed to characterize soil strength, a portable testbed that mimics the flight system is designed and built using commercial off-the-shelf components. A data-processing pipeline is developed to convert raw measurements to soil strength. Tests were performed on three characterized simulants with different mechanical properties. The results show that the abrading bit is capable of making shear and bearing strength measurements with quantified uncertainties and demonstrate, for the first time, the ability to perform controlled geotechnical analysis using a standard science instrument.

Data Pre-Processing and Signal Analysis of Tianwen-1 Rover Penetrating Radar

The Rover-mounted Subsurface Penetrating Radar (RoSPR) is one of the scientific payloads onboard China’s first independent Mars exploration mission, Tianwen-1. The radar aims to characterize the thickness of the upper Martian soil and investigate the subsurface stratigraphy by collecting and processing the data. This article is mainly divided into two parts, the introduction of data pre-processing and analysis of pre-processed radar signals, aiming at helping scientists make more effective use of radar data. The first part describes the operating principle of the RoSPR and the procedure of radar data pre-processing at all levels. Data pre-processing is mainly designed to transfer the raw data format to a common PDS (Planetary Data System) and eliminate the influence of the instrument. In the signal analysis part, the performances of both self-check signals and echo signals of low- and high-frequency channels are analyzed, which indicate a stable radar system and are useful for background removal. Phase and time calibration is of great importance for improving data quality and making the radar data more accurate. Moreover, further processing is required to obtain clear radar images, such as filtering, background removal and gain setting.

In‐Flight Calibration of Near‐Infrared Reflectance Spectra Measured by the Zhurong Mars Rover

AbstractThe Zhurong rover of the China's first Mars Exploration Mission successfully landed on the northern plain of Mars and measured near‐infrared (NIR) reflectance spectra with the Mars Surface Composition Detector (MarSCoDe). There was only orbital NIR hyperspectral data before the success of the Zhurong and Perseverance rovers in 2021. The in situ spectral measurements by the rover face different problems when compared with orbital measurements in data analysis, and thus need a new process pipeline. We analyzed the factors affecting the quality of the NIR spectra acquired by the Zhurong rover, including temperature variation of the detector, non‐homogeneous properties of the calibration panels, the atmosphere transmission and Martian dust buildup on the calibration panels. We then identified that the Martian dust buildup on the calibration panels is the main factor affecting the spectra, causing significant discrepancies between the reflectance calibrated with the white and gray panels, respectively, and the systematically higher reflectance values of the Martian soils measured by the Zhurong rover than those by other missions. We proposed a spectral unmixing strategy to restore the radiance of clean calibration panels on the rover and then derived the reflectance spectra with an uncertainty of ∼14%. The method has been tested by simulation experiments in laboratory. The data quality of the in situ NIR spectra of the Zhurong rover is significantly improved after the calibrations based on our pipeline, which is critical for mineral identification on small scales and calibrations of the orbital remote sensing data.

Experimental study on the ignition and combustion of Mg particles enhanced by metal oxides in CO2

Due to the high cost and long lifecycle of manned Mars exploration missions, in-situ resource utilization technology, including Mg/CO 2 processes, has attracted increasing attention. At present, Mg/CO 2 engines face the challenges of long ignition delay, serious carbon deposition, and low combustion efficiency. The root of these challenges lies in the Mg/CO 2 combustion reaction. Therefore, based on an Mg-based powder prepared by mechanical mixing combined with ultrasonic dispersion, the effects of various nano-metal oxides (CuO, Fe 2 O 3 , MnO 2 , MoO 3 , and Bi 2 O 3 ) on the ignition and combustion of Mg particles in CO 2 were studied through constant volume combustion experiments. It was found that MoO 3 undergoes the optimal covered-type of binding with Mg particles. The other oxides achieved embedded-type binding, of which MnO 2 binding was the worst. The enhanced ignition and combustion effects of Bi 2 O 3 and CuO were best. Thermogravimetric analysis found that CuO and Bi 2 O 3 improve combustion efficiency by lower ignition temperatures, inhibiting low-temperature oxidation reaction and increasing reaction ratio. • The enhancement effects of metal oxides on ignition and combustion of Mg particles in CO 2 are firstly studied. • The binding abilities of different nano-metal oxides to micro-Mg particles are analyzed. • The enhancement effects of CuO and Bi 2 O 3 on ignition and combustion of Mg particles in CO 2 are analyzed. • The influences of metal oxide addition ratio on enhancement are analyzed.

Gradeability of ‘Zhu Rong’ Mars rover based on the simulated Martian terrain

Due to the long-term weathering and erosion climate, many craters terrains on the surface of Mars are covered with loose weathered sedimentary debris, and Mars rovers traversing these slope-like terrains with soft soils will easily slip or even sink, and may affect the survey missions. Therefore, it is important to study the climbing ability of Mars rovers for Mars exploration missions. This work testes the climbing capability of 'Zhurong' Mars rover based on active–passive suspensions under the simulated Martian terrain and soil parameters were adequately measured. The maximum climbing distance (MCD), slip rate, power, current, energy, and efficiency are analyzed to explore the climbing abilities under different climbing methods, soil states and dynamic parameters (speeds, angular velocity) settings. The test results show that the peristaltic mode is able to continue climbing after a direct climb failure, and the MCD per period is influenced by angular velocity. The power and current data can effectively reflect the difficulty of the rover climbing. Under the same dynamic parameters, the greater the slip rate of the rover, the larger the output power and current. In addition, the speed should be minimized to prolong the climbing distance, no matter it is direct or peristaltic climbing.

Observations and interpretations of geomorphologic features in the Tianwen-1 landing area on Mars by using orbital imagery data

China’s first Mars exploration mission, Tianwen-1, successfully landed in southern Utopia Planitia on Mars on May 15, 2021. This work presents a detailed investigation of the geologic context of the landing area surface for this mission based on orbital remote-sensing data. We constructed a geomorphologic map for the Tianwen-1 landing area. Results of our detailed geomorphologic map show several major landforms within the landing area, including rampart craters, mesas, troughs, cones, and ridges. Analysis of materials on the landing area surface indicates that most of the landing area is covered by Martian dust. Transverse aeolian ridges are widely distributed within the landing area, indicating the surface contexts were (and still are) modified by regional winds. In addition, a crater counting analysis indicates the landing area has an absolute model age of ~3.3 Ga and that a later resurfacing event occurred at ~1.6 Ga. Finally, we outline four formational scenarios to test the formation mechanisms for the geomorphologic features on the landing area surface. The most likely interpretation to explain the existence of the observed surface features can be summarized as follows: A thermal influence may have played an important role in the formation of the surface geomorphologic features; thus, igneous-related processes may have occurred in the landing area. Water ice may also have been involved in the construction of the primordial surface configuration. Subsequent resurfacing events and aeolian processes buried and modified the primordial surface.

Constraints on water activity at the Zhurong landing site in Utopia Planitia, Mars

Mineralogical evidence of water–rock interactions is a strong indicator of the presence of liquid water on ancient Mars. Previous observations have found widely distributed hydrated minerals in the southern highlands, whereas such discoveries have been rare in the younger northern lowlands. China’s first Mars exploration mission successfully landed a rover (Zhurong) in southern Utopia Planitia, providing an opportunity to analyze the exposed rocks in the northern lowlands. Using data from the short-wave infrared (SWIR) spectrometer and the laser-induced breakdown spectrometer (LIBS) onboard the Zhurong rover, we found evidence for the widespread presence of hydrated minerals (probably sulfates or silica) around the landing site. The basaltic-like elemental compositions of the targeted samples further indicated that hydrated minerals are likely minor components. The results from Zhurong suggest that active aqueous activities occurred during the overall cold and dry Amazonian era on Mars. However, further evaluations are needed on the duration and scale of these activities.

MarsNet: Automated Rock Segmentation With Transformers for Tianwen-1 Mission

The Mars exploration mission of China named Tianwen-1 is being carried out as scheduled. The Navigation and Terrain Cameras (NaTeCam) equipped on the Zhurong Rover play an essential role in obstacle recognition. The main obstacles on the Martian surface are rocks of different sizes, which influence the path planning of Zhurong Rover in scientific exploration. Most existing semantic segmentation methods are based on the U-Net architecture with ResNet or other backbones, and features extracted by these methods lack of the long-range dependencies. To fully exploit the context information, we propose the MarsNet framework for Mars image, which combines Transformers with the convolutional neural network as the backbone, and hybrid dilated convolution (HDC) is also employed to the decoder path to help detect the huge rocks. Besides, since there are few open-source datasets for rock segmentation for Mars, we establish a segmentation dataset from Martian surface image, named TWMARS, captured by NaTeCam. Extensive experiments are conducted on TWMARS dataset, and the experimental results demonstrate that MarsNet achieves accurate rock segmentation and outperforms state-of-the-art methods. The source code is available at: https://github.com/BUPT-ANT-1007/MarsNet.

Effect of Different Geometric Porosities on Aerodynamic Characteristics of Supersonic Parachutes

The supersonic parachute plays an important role in the descent and landing of Mars missions. Next-generation supersonic parachutes, such as disksail parachutes, are alternatives to disk-gap-band (DGB) parachutes. Disksail parachutes have larger porous gaps and smaller porous seams on the canopy surface than DGB parachutes. To date, the influence mechanism of porous seams or gaps and their locations on the performance of supersonic parachute systems in Martian atmospheric conditions remains unclear. In this study, different canopy models with seams and gaps based on NASA’s supersonic disksail parachutes were designed, and the aerodynamic characteristics of such geometric porosity models were studied numerically. For seam-only models, the drag coefficient of the parachute decreases when the position of the seam is close to the middle of the canopy. When the seam is close to the mouth of the canopy, the pressure difference between the inner and outer surface of the canopy becomes small, reducing the risk of tearing the canopy. For gap-only models, the drag coefficient of the middle gap model is higher, while the lateral force stability of the top gap model is better. The results show that the addition of a seam can improve the drag performance of the top gap model and improve the lateral stability of the canopy with the middle gap. This study provides some theoretical references for designing the porosity of parachutes under different requirements for Mars exploration missions in the future.

Unified Multirate Control: From Low-Level Actuation to High-Level Planning

In this article, we present a hierarchical multirate control architecture for nonlinear autonomous systems operating in partially observable environments. Control objectives are expressed using syntactically co-safe linear temporal logic (LTL) specifications and the nonlinear system is subject to state and input constraints. At the highest level of abstraction, we model the system–environment interaction using a discrete mixed observable Markov decision process, where the environment states are partially observed. The high-level control policy is used to update the constraint sets and cost function of a model predictive controller (MPC) which plans a reference trajectory. Afterward, the MPC planned trajectory is fed to a low-level high-frequency tracking controller, which leverages control barrier functions to guarantee bounded tracking errors. Our strategy is based on model abstractions of increasing complexity and layers running at different frequencies. We show that the proposed hierarchical multirate control architecture maximizes the probability of satisfying the high-level specifications, while guaranteeing state and input constraint satisfaction. Finally, we tested the proposed strategy in simulations and experiments on examples inspired by the Mars exploration mission, where only partial environment observations are available.

Geochemical bio-signatures in Martian analogue basaltic environments using laboratory experiments and thermochemical modelling

The identification of geochemical bio-signatures is important for assessing whether life existed on early Mars. In this paper, experimental microbiology and thermochemical modelling were combined to identify potential inorganic bio-signatures for life detection on early Mars. An analogue mixed microbial community from an analogue terrestrial fluvio-lacustrine environment similar to an ancient lacustrine system at Gale Crater was used to study microbial dissolution of a basalt regolith simulant and the formation of bio-signatures over a short time frame (1°month) at 14°C, 2 bar. Microbial growth influenced element dissolution (Mg, Fe, Mn, Ca and K) and the formation of morphologies and Fe-Si amorphous layers on mineral surfaces. Thermochemical models were performed at 14°C, 2 bar; the results were compared with experimental data to predict bio-signatures that would occur over geological timescales. The pH was varied to simulate abiotic and biotic experimental conditions. Model results suggest that, at water to rock ratios of 100 to 38, a less complex secondary mineral assemblage forms during biotic dissolution compared to abiotic weathering. Carbonates, quartz, pyrite and hydroxyapatite form under biotic conditions, whereas in the abiotic system magnetite and phyllosilicates would also precipitate. These results could be used to distinguish between abiotic and biotic basalt weathering processes, aiding the interpretation of data from Mars exploration missions.

主小行星带对火星轨道长期动力学影响评估

<p indent="0mm">The successful implementation of the Tianwen-1 mission marks that China is moving toward a deeper space beyond the moon, facing a more complex space dynamics environment, and the difficulty of deep space exploration will continue to increase. The main belt asteroids (MBAs) are adjacent to Mars, and the perturbation by MBAs is hard to fully consider, effecting the accuracy of the Mars orbital dynamics parameters. Thus, it will indirectly affect the construction of a high-precision solar system ephemeris and the Mars exploration missions. This paper analyzes the distribution feature of MBAs based on the Nesvorný asteroid library. The dynamic environment of the whole solar system with MBAs was established to evaluate MBA’s perturbation influence. The results show that the difference between the ten-year integral orbits of the inner solar system planets and DE421 is less than <sc>15 m,</sc> and the integral difference of Mars’ orbits reaches<sc>100 m.</sc> Based on the point-mass model, the one-ring model and the latest six-ring model, the influence of MBAs on the orbit of Mars is estimated, and the orbit error of <sc>10 years</sc> is about <sc>2 km,</sc><sc> 31.3 m,</sc> and <sc>2 m,</sc> respectively. Further, the joint solution of the ring model and the orbital parameters of the planets is discussed, which confirms that the residuals of Mars-Earth distance with the fitted ring model can theoretically be reduced to sub-meters. The error in the <italic>Z</italic>-axis of the planet’s orbit is large if use only the range measurement.

Design and manufacturing of a highly integrated optical module for Tianwen-1 probe's landing LiDAR

In this study, a highly-integrated optical module based on micro-electromechanical system (MEMS) mirror, glass with low thermal expansion coefficient, a higher-order aspheric lens with high refractive index and two position-optimized optical filters is proposed. The Mars exploration mission requirements and the non-coaxial optical path of the optical module are discussed, while the relationship between the signal-to-noise ratio (SNR) and the detection distance, as well as between the scanning field of view(FOV)and the entrance pupil diameter, is given. The transmitting module consisting of a scanning device and angle magnifier has a temperature range of −20 °C to +40 °C, and a good reliability at 1800 g@4000 Hz. The receiving module using two ZnS lenses and two narrow-band filters with bandwidths of 22 and 10 nm has an f number of 0.55, a back working distance of 3.24 mm and a normalized energy collection efficiency at the edge of the FOV of 72.8%. The presented optical module has a Ø30°FOV, 120 m detection distance and 2 mrad angular resolution, and has been successfully applied to Tianwen-1 Probe's landing LiDAR.

Key Parameters of a Design for a Novel Reflux Subsonic Low-Density Dust Wind Tunnel

The dust storm on the surface of Mars is a severe threat to Mars exploration missions. Taking adequate measures to avoid the impact of the harsh wind-blown dust environment is indispensable. Ground simulation of the Martian high-speed windblown dust environment is helpful for analysis of the environmental effects and evaluations of the suitability of the components and materials. In this paper, a novel reflux subsonic low-density dust wind tunnel is presented to simulate the high-speed windblown dust environment of the Martian atmosphere with a velocity of more than 100 m/s. The sand and dust are fed into the wind tunnel through the ejector assembly together with the compressed gas, resulting in high uniformity of particles in the test section. The construction design of the Mars wind tunnel is introduced. The key parameters, which are the nozzle parameters and the contraction curve, are discussed in detail. The convergent nozzle is most suitable for the ejector assembly. Moreover, the bicubic curve is selected as the contraction curve. The gas-particle two-phase computational fluid dynamic (CFD) simulations demonstrate the rationality of the wind tunnel design.