Mars Exploration Missions Research Articles

3D morphometry of Martian craters from HRSC DEMs using a multi-scale semantic segmentation network and morphological analysis

The morphology of impact craters reveals the structure and composition of the Martian surface, especially the subsurface conditions and Martian geological history, which have increasing importance in Mars exploration missions. This work presents a 3D morphometric method for detecting and delineating Martian craters, and a 3D morphological analysis was conducted. Specifically, this work first focused on the segmentation of Martian craters. Based on the segmentation results, clustering of crater instances was then carried out. Finally, with the individual craters that were extracted, a morphological analysis involving the measurements of their diameter, depth, area, RMS height, rim height, circularity, and the statistics thereof was performed. Unlike previous studies, which have mainly used optical images and object detection approaches, this work regards crater extraction as a semantic segmentation task instead of an object detection task to better delineate the precise shape and boundary information. Digital elevation model (DEM) was utilized as primary data to directly obtain 3D information, which was converted into 3D point cloud format and fed to a multi-scale semantic segmentation network. The semantic segmentation results achieved an overall accuracy of 0.932 and mIOU of 0.871 on the test data. We automatically counted 63 craters in Noachis Terra and 40 craters in Terra Cimmeria. The 3D morphological measurements showed that 66% of the impact craters in the first region were larger than 10 km in diameter, while 50% of the impact craters in the second region were larger than 10 km. In both areas, craters could reach a maximum depth of 2000 m. With the proposed method, we can automatically conduct 3D morphological measurements of Martian craters with high efficiency that is improved by 15 times compared with that of manual crater analysis tools. The achieved 3D morphometric results can provide a reference and support for future research on Martian landforms.

The research of thermal environment test methodology for the Mars probe product

Abstract In order to ensure the success of the Mars exploration mission, it is necessary to accurately simulate the unique environment on the surface of Mars in a ground test and verify the effectiveness of the thermal control measures of the Mars rover. This paper proposes a thermal balance test method that can simultaneously simulate environmental factors such as Martian surface gas atmosphere, wind speed, pressure, solar radiation, and atmospheric temperature. This proposed test method meets the thermal design verification requirements of component-level products. Compared with similar large-scale facilities, the test cost is low, and the implementation efficiency is high. Furthermore, the influence of the Martian wind field on the surface temperature distribution of the product under both the Martian day and night environment was investigated using the proposed test method. The research results show that although the atmospheric pressure on the surface of Mars is much lower than the surface of the Earth, the Martian wind will still form forced convection heat transfer on the surface of the probe and its auxiliary products, which will affect the heat distribution of the products. In the thermal control design of the products, it is necessary to consider the impact of all the above environmental factors and carry out corresponding comprehensive environmental test verification.

Pixel-level Terrain Processing of the Martian Surface from Moderate Resolution Images of Tianwen-1

The moderate-resolution camera (MoRIC) of the Tianwen-1 orbiter, China’s first Mars exploration mission, is a frame-imaging scheme color camera. However, generating a precise digital elevation model (DEM) from these images faces challenges due to the presence of featureless and repetitive regions on the Martian surface. Traditional photogrammetric methods often struggle to achieve pixel-level resolution in these areas. To address this, we employ a shape from shading (SFS) algorithm that leverages shading patterns to reconstruct fine-scale terrain details, optimizing photogrammetric initial DEM. This paper presents a novel global bisection search algorithm, based on the Pearson correlation coefficient to determine the smoothing parameter, a crucial element in the SFS process. Comparisons with higher-resolution data from the Mars Express high-resolution stereo camera and Mars Reconnaissance Orbiter CTX images validate our approach, highlighting the potential of SFS to significantly enhance the scientific value of Tianwen-1 MoRIC data by generating high-resolution, three-dimensional maps of Mars.

Space exploration in China

Abstract In the past 20 years, China has implemented Manned Space Engineering, Lunar and Mars exploration missions, becoming an active participant in human space travel and exploration. So far China has established its Space Station in 2022, continuing to carry out large-scale space science research for the next 10-15 years. China has successfully achieved the soft landing on the lunar, far side of the Moon and on the Mars surface, obtained 1.73 kg of lunar sample, and will also implement the lunar Antarctic sample return and Mars sample return mission later. The exploration missions for the asteroid and Jupiter system are being prepared. Overall the future science exportations and collaborations between human and robot, as well as the utilisation of extraterrestrial resources will become the new development focus. Chinese scientists eagerly look forward to close international collaboration.

Exploring the dielectric loss of Martian regolith in the frequency domain using Zhurong radar data

Martian regolith is one of the primary science objectives of Mars exploration missions. The Rover Penetrating Radar carried by Zhurong rover allows for high-resolution subsurface imaging and in-situ measurements of Martian regolith dielectric properties, which are crucial to advance our understanding of Martian geology and hydrological evolution. While earlier studies have derived dielectric constants for the shallow subsurface, further characterization of subsurface materials requires the determination of attenuation properties. In this study, we applied the centroid-frequency shift method to explore the attenuation property of the Martian regolith in the frequency domain. Lateral attenuation variation was analyzed in detail by integrating subsurface radargram and navigation terrain images. The results show that, within a depth of ∼4 m, the attenuation of radar signal for Zhurong subsurface material is equal to a loss tangent of 0.0079, with a standard deviation of 0.001. Based on the loss tangent value, dielectric permittivity and ground characterization, we preclude the possibility that the regolith is predominantly igneous materials. The lateral variation of the attenuation property could likely be attributed to changes in the proportion of duricrusts, which are heterogeneously distributed along the rover traverse. Our findings offer valuable information for understanding the Martian regolith and its evolution, serving as a important reference for future Mars sample return missions.

Mars Exploration: Research on Goal-Driven Hierarchical DQN Autonomous Scene Exploration Algorithm

In the non-deterministic, large-scale navigation environment under the Mars exploration mission, there is a large space for action and many environmental states. Traditional reinforcement learning algorithms that can only obtain rewards at target points and obstacles will encounter the problems of reward sparsity and dimension explosion, making the training speed too slow or even impossible. This work proposes a deep layered learning algorithm based on the goal-driven layered deep Q-network (GDH-DQN), which is more suitable for mobile robots to explore, navigate, and avoid obstacles without a map. The algorithm model is designed in two layers. The lower layer provides behavioral strategies to achieve short-term goals, and the upper layer provides selection strategies for multiple short-term goals. Use known position nodes as short-term goals to guide the mobile robot forward and achieve long-term obstacle avoidance goals. Hierarchical execution not only simplifies tasks but also effectively solves the problems of reward sparsity and dimensionality explosion. In addition, each layer of the algorithm integrates a Hindsight Experience Replay mechanism to improve performance, make full use of the goal-driven function of the node, and effectively avoid the possibility of misleading the agent by complex processes and reward function design blind spots. The agent adjusts the number of model layers according to the number of short-term goals, further improving the efficiency and adaptability of the algorithm. Experimental results show that, compared with the hierarchical DQN method, the navigation success rate of the GDH-DQN algorithm is significantly improved, and it is more suitable for unknown scenarios such as Mars exploration.

Numerical study on aerodynamic characteristics of Mars parachute system with different combinations of fabric permeability and structural porosity

Supersonic parachute plays a crucial role in Mars exploration missions. However, future's large payload exceeds the maximum allowed one of disk-band-gap parachute, new generations of supersonic disksail and ringsail parachute had failed in their flight tests, which may be related to their complicated permeabilities (fabric permeability and structural permeability). Till now, most effects on fabric permeability are mostly considered in subsonic flows, and the influence mechanism of fabric permeability under supersonic conditions is rarely reported. In this study, different permeability schemes (including fabric and structural permeabilities) are designed for a supersonic disksail parachute system. The influence of different ratio of structural permeability to fabric permeability under same total porosity on the flow fields around a parachute system and aerodynamic performance is compared and analyzed. As a result, when the ratio of structural permeability to fabric permeability is 5:5, the stability of parachute shows better than other air permeability schemes. When the ratio is 7:3, the canopy has the best drag performance. With the contribution of fabric permeability increased from 30% to 70%, the drag performance of parachute presents a decreasing trend. Then, the porosity schemes with better aerodynamic performance are placed under Martian atmosphere conditions. The results show that in supersonic flows, when the ratio is 7:3, the aerodynamic performance of parachute is better. In transonic stage, the parachute with ratio of 7:3 has better drag performance, while the parachute with ratio of 5:5 has better stability. In subsonic stage, the parachute with ratio of 5:5 has better drag and stability performance.

Magnetohydrodynamic Modeling of Background Solar Wind near Mars: Comparison with MAVEN and Tianwen-1

Combined with data assimilation methods, a three-dimensional magnetohydrodynamic (MHD) numerical model is an effective tool to explore the mechanism of space weather. As a driver of space weather, the dynamic development of stream interaction regions (SIRs) near the orbit of Mars is an area of active research. In this study, we use the interplanetary total variation diminishing (TVD) MHD model to simulate solar wind parameters and model SIRs near Mars from 2021 November 15 to 2021 December 31. In this model, the MHD equations are solved by the conservation TVD Lax–Friedrichs scheme in a rotating spherical coordinate system with six component meshes used on the spherical shell. Solar wind velocity, density, temperature, and magnetic field strength are given at the inner boundary due to the characteristic waves propagating outward. We compared modeled results with observations from Mars Atmospheric Volatile EvolutioN (MAVEN) and Tianwen-1 (China’s first Mars exploration mission). Statistical analysis shows that the simulated results can capture SIRs and are in good agreement with observations; moreover, the assimilated results based on the Kalman filter improve the accuracy of numerical prediction compared with simulated results. This paper is the first attempt to simulate SIR events combined with MAVEN and Tianwen-1 in situ observations. Our work demonstrates that using the MHD model with the Kalman filter to reconstruct solar wind parameters can help us study the characteristics of SIRs near Mars, improve the capabilities of space weather forecasting, and understand the background solar wind environment.

Alkali Trace Elements Observed by MarSCoDe LIBS at Zhurong Landing Site on Mars: Quantitative Analysis and Its Geological Implications

AbstractMars Surface Composition Detector (MarSCoDe) is one of the important payloads carried by the Zhurong rover, China's first Mars exploration mission Tianwen‐1. The laser‐induced breakdown spectroscopy (LIBS) instrument of MarSCoDe is mainly used to detect major and trace elements on the surface of Mars. The quantitative analysis of alkali trace elements, namely lithium (Li), strontium (Sr), and rubidium (Rb), holds significance in unraveling the geological evolution of the Zhurong landing site. This study focuses on establishing univariate calibration models using MarSCoDe LIBS spectra from 84 samples tested in the ground laboratory. The accuracy of these models, within a few parts per million (ppm), was subsequently validated through the analysis of 12 onboard MarSCoDe Calibration Targets (MCCTs). With these models, Li, Sr, and Rb concentrations in the surface targets during the initial 300 sols (Martian days) traverse were determined. These concentrations ranged from 6 to 18, 106–628, and 22–87 ppm, respectively. Our results suggest that Li, Sr, and Rb are mainly related to the igneous rock components in the rocks and soils at the Zhurong landing site. The major secondary minerals in MarSCoDe scientific targets are likely small amounts of sulfates, which appear to have formed from the acidic weathering of recent surface brine. Clay minerals are likely either absent or very sparse in the scientific targets. The surface igneous materials at the landing site likely have originated from the most recent lava flow during the Amazonian epoch.

Martian Dust Storm Spatial‐Temporal Analysis of Tentative Landing Areas for China's Tianwen‐3 Mars Mission

AbstractChina's first Mars sampling return mission (Tianwen‐3) is designed to launch and retrieve samples around 2030. Three tentative landing areas (TLAs) (Amazonis, Chryse and Utopia Planitiae, i.e., TLA‐A, TLA‐C and TLA‐U) are selected based on elevation <−2,000 m and latitude between 17° and 30°N. As a dominant feature of Martian meteorology, dust storms manifest in all seasons and affect the accuracy and safety of Mars exploration missions. Tianwen‐3's landing, sampling and ascent phases are in the dust storm season. Therefore, analyzing dust storm activity around landing areas is significant for the Tianwen‐3 mission. According to Mars Daily Global Maps taken by Mars Orbiter Camera spanning Martian years 24–28, 2,476 dust storm events around the three TLAs were identified in this research. Dust storm temporal probabilities within TLA‐A, TLA‐C and TLA‐U were calculated as 0%–44.69%, 0%–66.29% and 0%–33.64%, separately. Dust storm spatial probabilities around the TLA‐A, TLA‐C and TLA‐U were computed, with ranges of 0%–10.71%, 0%–14.55% and 0%–19.96% during the T1 period (Ls = 161–309°), and 0%–6.75%, 0%–7.65% and 0%–8.26% during the T2 period (Ls = 342‐55°), respectively. Finally, considering the temporal and spatial distribution of dust storms, we recommend the T2 period as the launch scenario. Three safe periods (Ls = 2–18°, 4–12°, and 356–4°) were assigned for the entry‐descent‐landing (EDL) phase, along with one period (Ls = 45–55°) for the take‐off and ascent phase. Five circular landing zones with dust storm spatial probability <3% were selected for the Tianwen‐3 mission.

The Data Compression Method and FPGA Implementation in the Mars Rover Subsurface-Penetrating Radar on the Tianwen-1 Mission

Since Mars is far away from Earth, the propagation delay between Mars and Earth is very large. To ensure the effective use of the link transmission bandwidth, China’s first Mars exploration mission has put forward a demand for data compression for all scientific payloads. The on-board mature algorithms for data compression are mainly focused on optical images and microwave imaging radar applications. No articles have been published on data compression methods that are applied to subsurface-penetrating radar. Based on the background of this application, this paper proposes a logarithmic lossy compression algorithm which can meet the mission requirements for high compression ratios of 4:1 and 2.5:1. Its compression error is less than that of the block adaptive quantization (BAQ) algorithm. The algorithm is not only easy to implement on field-programmable gate array (FPGA) platforms, but also offers simple ground decompression and fast imaging. The experimental results show that high compression ratios of 4:1 and 2.5:1 can be realized, even if the data in and between traces do not have a strong correlation. And its relative error is less than 2%, which is a new type of high-efficiency data compression method that can be implemented on-board to meet with the demand of subsurface penetrating radar.

Report of the 6th (Virtual) Meeting on the Planetary Protection Knowledge Gaps for Human Missions to Mars on June 1–2, 2022

This paper reports the sixth in a series of meetings held under the auspices of COSPAR (with space agencies support) to identify, refine and prioritize the knowledge gaps that need to be addressed for planetary protection for crewed missions to Mars, as well as to describe where and how needed data can be obtained. This approach is consistent with current scientific understanding and COSPAR policy, that the presence of a biological hazard in Martian material cannot be ruled out, and appropriate mitigations need to be in place.The workshops in the series were intentionally organized to obtain a diverse set of inputs from subject matter experts across a range of expertise on conduct of a potential future crewed Mars exploration mission, identifying and leveraging precursor ground, cis-lunar crewed and Mars robotic activities that can be used to close knowledge gaps.The knowledge gaps addressed by this meeting series fall into three major themes: 1. Microbial and human health monitoring; 2. Technology and operations for biological contamination control, and; 3. Natural transport of biological contamination on Mars. This report describes the findings of the 2022 meeting, which focused on measures needed to protect the crew and the returning Mars samples during the mission, both on the Martian surface and during the return to Earth.Much of this approach to crewed exploration is well aligned with the Principles and Guidelines for Human Missions to Mars described in section 9.3 of the current (2021) COSPAR policy, in terms of goals and intent.There were three specific recommendations:•The crew should be considered as a unit, meaning if one individual gets sick it will be impractical for them to be isolated from the other crew member(s) (this differs from the current COSPAR Planetary Protection Policy language).•Pristine life detection/subsurface samples should be kept separate from the crew during the return trip, both to keep them pristine and to protect the crew. (If there are time sensitive measurement that need to be made during the return trip they could be made on a dedicated non-pristine set of samples).•An approach to break the chain of contact between Mars and the Earth is still needed to protect the broader biosphere, even if crew exposed on Mars appear unharmed.

Geochemical biosignature formation in experimental Martian fluvio‐lacustrine and simulated evaporitic settings

AbstractTo assess whether life existed on Mars, it is crucial to identify geochemical biosignatures that are relevant to specific Martian environments. In this paper, thermochemical modeling was used to investigate fluid chemistries and secondary minerals that would have evolved biotically over geological time scales in Martian fluvio‐lacustrine and evaporitic settings, and that could be used as potential inorganic biosignatures for life detection on Mars. Modeling was performed using fluid and rock chemistries relevant to Gale crater aqueous environments. Potential inorganic biosignatures were identified investigating alteration deposits found at the surface of a simulant exposed to short‐term bio‐mediated weathering and comparing experimental and modeling results. In a fluvio‐lacustrine setting (water/rock of 2000–278), models suggest that less complex mineral assemblages form during biotic basalt dissolution and subsequent brine evaporation compared to what would happen in an abiotic system. Mainly nontronite, kaolinite, and quartz form under biotic conditions, whereas celadonite, talc, and goethite would also precipitate abiotically. Quartz, sepiolite, and gypsum would precipitate from the evaporation of fluids evolved biotically, whereas nontronite, talc, zeolite, and gypsum would form in an abiotic evaporitic environment. These results could be used to distinguish products of abiotic and biotic processes, aiding the interpretation of data from Mars exploration missions.

The characteristic and size–frequency distribution of rocks at the Zhurong landing site, Mars

The rock characteristic and size–frequency distribution (SFD) on Mars are important for understanding the geologic and geomorphic history of the surface, for evaluating the trafficability of roving, and for planning the potential infrastructure construction. Tianwen-1, China’s first autonomous Mars exploration mission, formed an excavated depression during touchdown, which has been the deepest depression on the Martian surface so far compared with others. According to the images captured using the Navigation and Terrain Cameras (NaTeCams) onboard the rover, Zhurong, the SFD of rocks is calculated and compared inside the excavated depression, within and out of the blast zone. For the first time, the rock size distribution inside the excavated depression is obtained, exposing the geological features of the shallow subsurface on Mars at a depth of tens of centimeters, which will surely be important for future drilling missions. It is found that the rock abundance in the depression is smaller than the original abundance on the surface, and the distribution of rocks in the blast zone on the surface is greatly influenced by the touchdown. In addition, based on the fractal dimension of rock sizes, the rocks (>10 mm) at the shallow subsurface of the Zhurong landing site may experience two different geological processes.

High-Reliability and High-Precision Braking and Capture Control Technology of Tianwen-1 Probe

The Tianwen-1 probe, used in China’s first Mars exploration mission, features multiple flight phases, numerous spatial pointing constraints, and complex working modes. During the braking and capture process, it faces challenges such as uplink or downlink command delay, unique capture window, post-control “occultation”, short-time significant change in speed increment, and interference caused by low-frequency and low-damping solid–liquid flexible coupling oscillations. Therefore, high reliability, high autonomy, and high precision are required for the braking and capture process. As the executor of braking and capture control, the GNC (guidance, navigation, and control) subsystem of the orbiter employs an online orbit control strategy reconstruction method based on arc loss compensation to realize high reliability, the main engine anomaly recognition and a seamless switching scheme to realize high autonomy, and the attitude–orbit coupling control algorithm with thrust direction compensation to realize high-precision speed increment control. According to the on-orbit flight validation of the Tianwen-1 probe, the GNC subsystem of the orbiter has completed the braking and capture control task reliably and autonomously with millimeter-per-second-level accuracy, effectively ensuring the successful execution of subsequent landing and patrol tasks. This paper analyzes the online orbit control strategy reconstruction method, anomaly recognition and seamless switching method, and thrust vector control method of the braking and capture process and offers valuable insights for future interplanetary exploration flight control.

Numerical study on the influence of fabric permeability on the inflation process and aerodynamic characteristics of disk-gap-band parachute

Supersonic parachute plays a crucial role in Mars exploration missions. The disk-gap-band (DGB) parachute he been used in all the successful Mars exploration missions. The parachute is fabricated from different porous fabric materials, and the fabric permeability is an important design and performance parameter, now it has been proved that the fabric permeability of porous canopy has important effects on the complicated flow fields around the parachute and in turn effects the nonlinear deformation and aerodynamic performances of the flexible canopy. However, till now, the influence mechanism of fabric permeability on the fluid-structure interaction mechanism and aerodynamic performance of supersonic flexible porous parachute in the inflation process still remain unknown. Therefore, in this study, a fluid-structure coupling method was used to numerically simulate the inflation process of disk-gap-band parachute with different fabric permeability (i.e., different fabric materials), and the effect of fabric permeability on the aerodynamic performance of disk-gap-band parachute was also analyzed. The results showed that the fabric permeability has a significant effect on the inflation process of DGB parachute with different fabric materials. During the inflation process, the oscillation angle and drag coefficients of the parachute both gradually decreased with the increase of fabric permeability, while the stability performance of the parachute became more complicated. Furthermore, it was also found that the influence of fabric permeability was different under subsonic and supersonic conditions. The K5836-3 fabric used as canopy material has better stability under subsonic conditions, and the 42105 fabric material has the best stability under supersonic conditions.

Rover Attitude and Camera Parameter: Rock Measurements on Mars Surface Based on Rover Attitude and Camera Parameter for Tianwen-1 Mission

Rocks, prominent features on the surface of Mars, are a primary focus of Mars exploration missions. The accuracy of recognizing rock information, including size and position, deeply affects the path planning for rovers on Mars and the geological exploration of Mars. In this paper, we present a rock measurement method for the Mars surface based on a Rover Attitude and Camera Parameter (RACP). We analyze the imaging process of the Navigation and Terrain Camera (NaTeCam) on the Zhurong rover, which involves utilizing a semi-spherical model (SSM) to characterize the camera’s attitude, a projection model (PM) to connect the image data with the three-dimensional (3D) environment, and then estimating the distance and size of rocks. We conduct a test on NaTeCam images and find that the method is effective in measuring the distance and size to Martian rocks and identifying rocks at specific locations. Furthermore, an analysis of the impact of uncertain factors is conducted. The proposed RACP method offers a reliable solution for automatically analyzing the rocks on Mars, which provides a possible solution for the route planning in similar tasks.

Tianwen-1 and MAVEN observations of Martian oxygen ion plumes

There is a significant Martian ion escape channel called the “plume”. Due to the lack of multi-point, high-resolution field and particle detections, the energization mechanism and source region identification of ion plumes by in situ measurements remain unclear. China's first Mars exploration mission, Tianwen-1, provides us an opportunity to study ion escape owing to the high altitude of its apoapsis (∼3 RM, RM is Mars radius). In this study, we take advantage of the joint observations of Tianwen-1 and Mars Atmosphere and Volatile EvolutioN (MAVEN) to study oxygen ion plumes. Our statistical results confirm the convection electric field acceleration as the energization mechanism of plume ions (up to >15 keV) in a more direct way than ever before. Our estimation suggests that most ion plumes originate from middle and low MSE (Mars Solar Electric) latitude of the northern dayside Martian ionosphere. This work improves our understanding of the pick-up process of the Martian escaping ions.

Space-deployable device based on shape memory cyanate ester composites

Shape memory cyanate ester is a class of shape memory polymers with high thermal stability and excellent space environmental adaptability. In this study, a space-deployable device based on cyanate ester-based shape memory polymer composite (CE-SMPC) was proposed, and its thermomechanical properties and shape memory behavior were experimentally evaluated. The space-deployable device maintained a high shape fixity rate even after prolonged exposure to high or low temperatures, which ensured its locking reliability in space applications. The results of self-deployment experiments indicated that the space-deployable device exhibited good shape recovery performance in both atmospheric and vacuum environments. The SMPC-based space-deployable device presented in this study was applied to China's first Mars exploration mission to achieve autonomous locking and release of the deployable engineering measurement subsystem on the probe.

Design and Realization Separable Observation Sensors of Tianwen-1 Mars Probe

Tianwen 1 Mars exploration mission is a high-risk mission with long cycle, high communication delay, high product reliability and harsh deep space environment. Two separate observation sensors are installed on Tianwen 1 probe. During the Earth Mars transfer phase of Tianwen 1, the first separable observation sensor was separated from Tianwen 1, which monitored the state of Tianwen 1 and its surrounding space environment. On the Mars orbit, the second separable observation sensor was separated from the Tianwen 1 probe and took a color group photograph of the Tianwen 1 probe and Mars. This paper first introduces the task requirements of separable observation sensors and the design constraints of deep space environment on products. Secondly, the composition of the separable observation sensor is introduced. Thirdly, the relevant indicators of the separable observation sensor are introduced. Finally, the ground test and in orbit test of the separable observation sensor are introduced.