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China'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. Plain Language Summary: Tianwen‐3 is the first Mars sampling return mission by China, scheduled to launch and return samples around 2030. Three tentative landing areas (TLAs), Amazonis Planitia (TLA‐A), Chryse Planitia (TLA‐C), and Utopia Planitia (TLA‐U), located at elevations of <−2,000 m and within the latitude range of 17°–30°N. Three TLAs are situated along the trajectories of Martian dust storm sequences. The harsh dusty conditions significantly impact the success of the Mars exploration mission. Therefore, it is meaningful to analyze the dust storm occurrence probability within and around three TLAs. In this study, we utilized Mars Global Surveyor (MGS) Mars Daily Global Maps to (a) detect the dust storm events around three TLAs in five consecutive Mars years (MY 24–28); (b) calculate and analyze the temporal and spatial probabilities of dust storm occurrence; and (c) designate the safe landing areas, the preferred take‐off and ascent and entry‐descent‐landing (EDL) periods for the Tianwen‐3 mission. Key Points: Dust storms within three tentative landing areas exhibit distinct seasonality and heterogeneity throughout a Mars year, with clear solstitial pause periodsDust storm spatial‐temporal analysis reveals that the T2 period is more suitable as the launch scenario for the Tianwen‐3The preferred entry‐descent‐landing period, preferred take‐off and ascent period, and safe landing areas are chosen for the Tianwen‐3 [ABSTRACT FROM AUTHOR]

Precisely constraining the shock pressure of a Mars sample is critical for revealing the shock condition, geological process, and habitability of the Martian surface. The crystal structure of plagioclase is sensitive to the moderate shock pressure, such that its infrared spectra may record the shock state of Martian materials. In this study, we present a new way for quantifying the shock pressure via the micro‐FTIR spectra of plagioclase by re‐analyzing the published spectra of experimental shocked feldspars. Using the absorption area of micro‐FTIR in the range of ∼1,000–1,150 cm−1, the shock pressures of plagioclases from three types of Mars meteorites were constrained. The results show that the nakhlite Northwest Africa (NWA) 10645, shergottite Tindouf 002, and martian breccia NWA 11220 have the shock pressure of 18.5 ± 5.2 GPa, >30 GPa, and 0–24.2 GPa, respectively. Our work demonstrates that the micro‐FTIR spectra of plagioclase is not only a quantitative tool for constraining the moderate shock pressure (<30 GPa) of Martian materials but also a useful technique for recognizing the high‐pressure phase maskelynite from plagioclase‐glass and evaluating the shock effects of Mars samples. In the future, this method will be available for the analysis of Mars samples returned by China's Tianwen‐3 mission in around 2030. Plain Language Summary: Tianwen‐3 mission is planned to return Mars samples to the Earth in around 2030. Revealing the shock features (e.g., shock pressure) of these Martian materials is critical for understanding the impact process, shock environment, and habitability on Mars. By re‐analyzing the published micro‐FTIR spectra of experimental shocked feldspars, a new method for quantifying the shock pressure of Mars samples has been represented. Then, the shock pressures of three Martian meteorites (nakhlite meteorite NWA 10645, shergottite meteorite Tindouf 002, and breccia meteorite NWA 11220) were constrained (i.e., 18.5 ± 5.2 GPa, >30 GPa, and 0–24.2 GPa, respectively). Our results demonstrate that the micro‐FTIR is a quantitative tool for constraining the moderate shock pressure (<30 GPa) of Martian materials. This method will provide us with a fast, low‐cost, and non‐destructive analytical approach to reveal the shock conditioning of Martian samples and other planetary materials. Key Points: A way was presented for constraining the shock pressure of the Mars sample via the micro‐FTIR spectra of plagioclaseNorthwest Africa (NWA) 10645, Tindouf 002, and NWA 11220 have the shock pressure of 18.5 ± 5.2 GPa, >30 GPa, and 0–24.2 GPa, respectivelyThis method is available for the analysis of Mars samples returned by Tianwen‐3 mission in around 2030 [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The radio occultation method, one of the methods used to provide planetary atmospheric profiles with high vertical resolution, was applied to China's first Mars mission, Tianwen-1. We carried out observations based on the Chinese Deep Space Network, and one-way, two-way, and three-way modes were used for Doppler observations from the Tianwen-1 spacecraft. We successfully obtained effective observations from Tianwen-1 on 22 and 25 March 2022. An inversion system developed for Tianwen-1 radio occultation observations enabled the derivation of neutral atmospheric density, pressure, temperature, and electron density profiles of Mars. Utilizing one-way tracking data, Martian ionospheric electron density profiles were retrieved at latitudes between 68.7 and 70.7 degrees (N). However, the presence of strong random walk noise in one-way tracking data led to poor inversion results. Meanwhile, Martian ionospheric electron density and neutral atmosphere profiles were extracted from two-way and three-way tracking data at latitudes between 55.1 and 57.0 degrees (S) on 22 March and at latitudes between 62.8 and 63.4 degrees (S) on 25 March. Importantly, our inversion results from Tianwen-1 maintained consistency with results from the Mars Express and the Chapman theory (mainly in the M2 layer). Through two days' observation experiments, we established and verified the occultation solution system and prepared for the follow-up occultation plans. [ABSTRACT FROM AUTHOR]

Hydrated minerals provide direct indications of the early Martian water environment. The various clay minerals and evaporite salts found to date are mainly exposed in the ancient southern highlands of Mars. While it is believed that the area of the northern lowlands could have hosted a global ocean in the past, its surface is covered with a layer of spectrally nonabsorbing materials, and orbital hyperspectral remote sensing has found only sparse evidence for the presence of water. China's first Mars exploration mission, Tianwen-1, landed in the putative ancient shoreline zone of the northern lowlands of Mars. Its rover, Zhurong, conducted high-spatial-resolution reconnaissance to reveal the geological and environmental evolution of this region. Owing to frequent dust storms, not only is the Martian surface covered with dust, but also the spectral calibration panels on the rover are affected by dust coverage. Data from the shortwave infrared (SWIR) spectrometer onboard the rover are also affected by other environmental factors such as instrumental temperature changes and atmospheric carbon dioxide absorption. This study recalibrated the in situ SWIR data to minimize the impact of the above factors. The recalibrated spectral data show that the reflectance of the landing area falls within the normal range of Martian soil, and confirm the presence of several important absorption peaks. The absorption characteristics indicate the presence of polyhydrated sulfates, gypsum, and hydrated silicates in the surface materials along the rover track, with sulfate content of <27–39 wt.%. Our results further confirm past activity of liquid water in the Zhurong rover landing area, providing mineralogical evidence supporting hypotheses related to underground water or an ancient shoreline. [ABSTRACT FROM AUTHOR]

Pitted cones are cone-shaped structures, spanning from meters to kilometers in size, characterized by summit depressions. They are widely distributed on the surface of Mars with various origins, such as rootless cones, mud volcanoes, cinder or scoria cones, tuff rings or cones, pingos, and dirt cones. If the pitted cones identified in southern Utopia Planitia are mud volcanoes, as is speculated, they could be of particular interest due to the fact that mud volcanoes on Earth bring sediments from a depth of meters to kilometers to the surface. In this study, we have investigated the pitted cones near Zhurong rover's landing site in southern Utopia Planitia, utilizing recent images and digital elevation models obtained from the High Resolution Imaging Camera instrument onboard China's Tianwen-1 orbiter. By leveraging the high-resolution images and digital elevation models, we have conducted a geometric measurement to distinguish the origin of pitted cones in the vicinity of the Zhurong rover. The morphological characteristics of these pitted cones indicate an explosive mud volcano origin. These explosive mud volcanoes could have formed by the violent eruption of subsurface overpressurized sediments generated from the combined effect of overburden pressure and anomalous high heat flow. The sediments forming the pitted cones in the northern plains could be the remnants of an ancient ocean. With future in-situ observations of these pitted cones, we hope to gain further insights into the sediments of the putative northern ocean, as well as the physical and chemical properties of the Martian subsurface during the formation of the pitted cones. [ABSTRACT FROM AUTHOR]

The Mars Surface Composition Detector (MarSCoDe) is a remote sensing instrument mounted on the front deck of the Zhurong rover in China's Tianwen-1 mission. The MarSCoDe adopts Laser-Induced Breakdown Spectroscopy (LIBS), along with Short Wave Infrared Spectroscopy (SWIR) and a telescopic micro-imager, to perform in situ detection of the chemical composition of soils, rocks, and minerals on the Martian surface. Since the MarSCoDe LIBS system works in extraterrestrial environments, it is important to equip the system with a set of onboard calibration targets, which are used for assessing the real-time performance of the instrument under various environmental conditions and conducting instrumental response calibration. Twelve dedicated LIBS reference samples were embedded as the MarSCoDe calibration target (MCCT) set, which plays a critical role in LIBS calibration before conducting LIBS analysis. This paper elaborates on the selection, development, characterization and testing of the MCCT set. The underlying scientific reasons and technical requirements that determine the selection of MCCT samples are introduced. The development procedures and mechanical performance test of both the calibration samples and the assembly holder are presented. Then, a comparison of the MCCTs and the characterization and scientific testing are described. The LIBS spectra of the MCCTs collected in three different atmospheric scenarios, namely laboratory-simulated Martian, normal terrestrial, and in situ Martian atmosphere, were investigated. The laboratory results and in situ behaviour show that the MarSCoDe instrument and the MCCT set can soundly adapt to the Martian environment with sufficient performance, as indicated by the fact that the spectral lines of the main elements in the calibration targets can be well identified and distinguished, including Ti, Si, Al, Fe, Mg, P, Ca, Na, K, O, C, H, S, etc. The MCCT samples provide a good reference for analysing Martian surface material composition and formulating the transfer relationship between the LIBS spectra measured in different atmospheric environments. [ABSTRACT FROM AUTHOR]

China's first Mars probe, the Tianwen-1, successfully landed on the Martian Utopia Plain on May 15, 2021. The multi-functional obstacle avoidance sensor (MOAS) has been the key navigation equipment for the entry, descent, and landing (EDL) operation of Tianwen-1. The MOAS integrates a landing camera and a laser imaging module and can acquire sequential optical images of the landing process of Tianwen-1 and high-resolution topography of the Martian surface. As a navigation sensor, the MOAS plays a key role in the processes of back cover avoidance, coarse obstacle avoidance, and hovering fine obstacle avoidance from the height of 10 km to landing. The MOAS's laser imaging module uses a new-generation scanning component, a two-dimensional MEMS scanning mirror, which is a unique feature compared to other space lidars. In this paper, optical and electronic designs of the MOAS are analyzed in detail. Based on the open-loop control feature of a MEMS scanning mirror, an online training and calibration method is proposed to increase the accuracy of optical angle control to 0.02°. In addition, the ground performance validation and the space environment testing of MOAS are described in detail. The inflight performance of MOAS is evaluated based on the sequential camera images and 3D point cloud data. In addition, the MOAS combines the attributes of a scientific instrument. The images obtained by the sensor can reconstruct the descending trajectory of Tianwen-1, determine accurate landing coordinates, and acquire information on the topography, surface reflectivity, and sand and dust of Mars. [ABSTRACT FROM AUTHOR]

The detection of lava tubes beneath the surfaces of the Moon and Mars has been a popular research topic and challenge in planetary radar observation. In recent years, the Moon–based ground penetrating radar (GPR) carried by the Chinese Chang'e–3/–4 mission, the RIMFAX radar carried by the Mars mission Perseverance, and the RoSPR radar and MOSIR radar carried by China's Tianwen–1 orbiter have extensively promoted the exploration of the underground space of extraterrestrial bodies, which is crucial for the future utilization and development of these spaces. This paper expounds on the principles, methods, and detection results of using GPR to detect lava tubes on the Moon and Mars. First, lava tubes' formation mechanism and morphological characteristics are outlined, followed by an introduction to GPR's working principles and classification. The advantages, disadvantages, and prospects of different types of radar in detecting the lava tubes are analyzed. Finally, the distribution of lava tubes on the Moon and Mars is briefly summarized, and the potential utilization of lava tubes is discussed. We believe that the GPR technique is an effective geophysical method for exploring the underground structures of the Moon and Mars, and the lava tubes beneath the surface of extraterrestrial bodies can provide important references for selecting future Moon and Mars bases. [ABSTRACT FROM AUTHOR]

Aqueous activities on Mars have gradually declined since the Noachian (>3.7 Ga). Although water can be stored in the subsurface during the latest epochs, geomorphological evidence is still limited. In this study, we used in situ imaging and spectral data acquired by China's Zhurong rover, as well as high‐resolution remote‐sensing data, to investigate the transverse aeolian ridges (TARs) in the Zhurong landing region of Utopia Planitia. A two‐stage evolutionary scenario of the TARs is proposed and polygonal features with hydrated minerals are identified for the first time on the surface of Martian TARs. We discussed the possible formation mechanisms of the polygonal features, and proposed that they could be related to recent aqueous activity and atmosphere‐surface water exchange on Mars, which sheds light on the hydrological cycle of Mars in current cold and dry climate. Plain Language Summary: The history of water on the surface of Mars has been studied for a long time. Since about 3.7 billion years ago, the role of water has gradually declined. Although the existence of subsurface ice on present‐day Mars has been confirmed, evidence for surface water is still limited. Transverse aeolian ridges (TARs), a kind of ripple‐like aeolian landform, are widely distributed on Mars and usually thought to be active within the last ∼3 million years. They are also identified in southern Utopia Planitia, the landing region of China's Mars exploration rover Zhurong. We analyzed the morphology and evolution of the TARs in the Zhurong landing region, and found some polygonal features with hydrated minerals such as gypsum on the surface of the latest‐formed TARs. We discussed the possible origins of these polygons, and proposed that they represent very recent aqueous activity on the Martian surface, which will help us better understand the hydrological cycle on current Mars. Key Points: Morphology and evolution of the transverse aeolian ridges (TARs) in the Zhurong landing region are studiedPolygonal features with hydrated minerals are identified on some of the TARs investigated by the Zhurong roverThe polygons could be related to very recent aqueous activity and atmosphere‐surface water exchange on Mars [ABSTRACT FROM AUTHOR]

Doppler radio tracking data from Tianwen-1, China's first Mars mission, could contribute to a better estimate of the gravity field of Phobos. In this study, we show that a determination up to degree and order 3 is feasible by considering five additional flybys of Phobos by the Tianwen-1 spacecraft, in addition to the previous flybys already done by the Mars Express spacecraft, and probably degree and order 5 is within reach. Three cases of mass repartition are considered: (i) a homogeneous case, (ii) a core-dominated Phobos, and (iii) a mantle-dominated Phobos. The case of a mantle-dominated Phobos is the easiest to detect, followed by a homogeneous Phobos, and finally by a core-dominated Phobos. We also discuss implications about the modelling of the internal structure of Phobos. [ABSTRACT FROM AUTHOR]

Combining the upstream solar wind observations measured by Mars Atmosphere and Volatile Evolution (MAVEN), Advanced Composition Explorer(ACE) and Deep Space Climate Observatory (DSCOVR) from October 2014 to April 2021, we investigate the statistical properties of the background solar wind at Mars and Earth. By applying an operational solar wind prediction system (Wang et al., 2018, https:// doi.org/10.1051/swsc/2018025) in Space Weather Prediction Center (SEPC), we simulate the solar wind conditions and carry out a comparative analysis with observations to study our model performance. We find that our model is able to simulate the solar wind conditions upstream of Earth and Mars, corresponding to the different heliocentric distances and different levels of solar activity. Furthermore, we apply an event-based evaluation by analyzing the high speed enhancements (HSEs), and find that the hit rate of HSEs is 70.38% and 66.37% for Earth and Mars, respectively. By predicting the HSEs at Earth (Mars), our model reaches a Mean Absolute Error (MAE) of 83.93 km/s (65.91 km/s) and 22.98 hr (21.65 hr) for maximum speed and arrival time prediction error, respectively. We also conduct a three-month case study, from November 2020 to January 2021, analyzing solar wind conditions upstream of Earth, Mars, and measured by Tianwen-1 (China's first Mars mission), for which our model is capable to predict the upstream solar wind conditions up to Mars. [ABSTRACT FROM AUTHOR]

A variety of aqueous deposits and soils from gullies, fluvial channels, mountain slopes, alluvial fans, playas, polygons, and yardangs have been found on Mars. However, the occurrence of sedimentary organic matter (SOM) in these landscapes under hyperarid and strongly radiative conditions has yet to be fully assessed. With various desiccated landforms analogous to those on Mars, the Qaidam Basin in northwestern China is considered a promising hyperarid Martian analog. Here, aqueous deposits and soils from nine landforms across the extremely dry northwestern Qaidam and from four landforms across the dry southeastern Qaidam were sampled and investigated. Our results reveal that landform and moisture are important controls on organic carbon distribution across the Qaidam Basin, while sedimentary origin has a dominant effect in the extremely dry northwestern Qaidam. Combined with previous studies, low organic carbon contents of soils in the extremely dry northwestern Qaidam suggest possibly low rates of microbial carbon input and of organic carbon degradation in Mars‐like environments. High organic carbon contents of aqueous deposits together with increasing trends along rivers indicate preservation of relic SOM and possibly slow degradation rates of organic matter as compared to their exposure timescale. Moreover, soils from the distal alluvial fan are found to favor the concentration of pedogenic organic carbon as compared to those from other landforms in the dry southeastern Qaidam and from all landforms in the extremely dry northwest. This suggests that subsoils in the distal fans are promising candidate targets for biosignature detection on Mars. Plain Language Summary: The search for life signals has been one of the most important objectives in Mars exploration. Since the launch of Viking 1 and 2, many landers and rovers have been sent to hunt for biosignatures on Mars. In addition to in situ detection, investigations of terrestrial Mars analog provide significant implications for life detection on Mars. Diverse dry water‐forming landforms including gullies, fluvial channels, mountain slopes, alluvial fans, playas, polygons, and yardangs in the Qaidam Basin, northwestern China, are analogous to those found on the Martian surface. To determine whether the aqueous deposits and soils can hold sedimentary organic matter (SOM) under Mars‐like conditions, we systematically investigated the surface and subsurface distribution patterns of organic carbon contents, moisture contents, pH, and mineral compositions in different landforms across the Qaidam Basin. Our results show that under extremely dry and strongly radiative conditions, different aqueous deposits are able to preserve residual SOM while soils contain very low contents of organic carbon on the surface. Moreover, we find that in the arid conditions, distal alluvial fans are promising candidates for soil organic carbon enrichment. These findings offer useful insights into the biosignature detection on Mars for future exploration missions. Key Points: The distribution of organic carbon contents in various aqueous deposits and soils across the Mars‐like Qaidam Basin has been investigatedResidual sedimentary organic matter of aqueous deposits can be preserved in the extremely dry northwestern Qaidam BasinSubsoils in the distal alluvial fan are ideal candidates for life detection on Mars [ABSTRACT FROM AUTHOR]

The trim flap is an aerodynamic control surface capable of allowing Mars entry vehicles to improve landing performance during the most dangerous entry, descent, and landing (EDL) phase. In present work, a deployable trim flap system was proposed to meet the aerodynamical trim requirement of the Tianwen-1 Mars probe, which provided a mass-saving alternative to the conventional use of the center-of-gravity (CG) offset of ballast mass. In order to guide the trim flap design, theoretical and finite element (FE) models were established to predict and evaluate the deployment performance. Then, a full-scale physical prototype was manufactured for deployment experiments to verify the design effectiveness as well as validate the theoretical and FE models. Results predicted by theoretical and FE models were in good agreement with deployment experiments. Furthermore, the effects of three factors on the deployment performance were investigated, including the non-linear behavior of the damping, acceleration environment, and backshell flexibility. The manufactured prototype was installed on the Tianwen-1 Mars probe, saving more than 300 kg when compared to the conventional use of ballast mass CG offset, and assisted Tianwen-1 in achieving a successful landing, making China the first country in the world to utilize the trim flap technology for Mars EDL. [ABSTRACT FROM AUTHOR]

The Zhurong rover of China's Tianwen-1 mission started its inspection tour on Mars in May 2021. As a major scientific payload onboard the Zhurong rover, the Mars Surface Composition Detector (MarSCoDe) instrument adopts laser-induced breakdown spectroscopy (LIBS) to detect and analyze the chemical composition of Martian materials. This paper introduces an experimental platform capable of establishing a simulated Martian atmospheric environment, in which a duplicate model of the MarSCoDe flight model is placed. In the simulated environment, the limit vacuum degree can reach 10−5 Pa level, the temperature can change from −190 °C to +180 °C, and different gases can be filled and mixed according to desired proportion. Moreover, the sample stage can move along a track inside the vacuum chamber, enabling the detection distance to vary from 1.5 m to 7 m. Preliminary experimental results indicate that this platform is able to simulate the scenario of MarSCoDe in situ LIBS detection on Mars well. [ABSTRACT FROM AUTHOR]

As part of China's first Mars exploration mission 'Tianwen-1', the Zhurong rover has successfully touched down on the surface of southern Utopia Planitia on May 15th 2021 and has been conducting surface operations for several months. A multispectral camera (MSCam), as an important payload onboard the Zhurong rover, aims to acquire multispectral images to investigate the morphological characteristics and mineralogic properties of the Martian surface. In this study, a detailed optimization design for the MSCam was carried out to achieve the abovementioned scientific objectives. The MSCam can perform multispectral imaging without chromatic aberration by utilizing eight narrow bandwidth filters made of glass of different thicknesses. Clear images of observation targets at different distances can be obtained by utilizing the six focal plane compensation lenses of varying thicknesses through the rotation of wheels. Calibration experiments, key specification tests and ground verification tests were also conducted in this study. Our results show that the pixel resolution of the MSCam can reach 0.146 mrad, the system static modulation transfer function (MTF) of the MSCam is better than 0.25@525 nm, and the signal-to-noise ratio (SNR) is higher than 40 dB, all of which allow clear imaging and accurate multispectral data acquisition of the targets. The high-resolution images obtained by the MSCam will provide detailed geological context for the data interpretation of other payloads on the rover, such as the Mars surface composition detector (MarSCoDe). The mineralogy information of the targets (e.g., fresh rock, dune) indicated by the MSCam multispectral data will also help to constrain the surface material composition of Mars. [ABSTRACT FROM AUTHOR]

On the great journey to Mars, China's first planetary exploration mission, the Tianwen-1 came within 26 million kilometers of Mars from 31 October 2020 to 25 January 2021 and was getting closer to its destination, the red planet, in search of answers to the cataclysmic climate change that occurred in Martian history. Both the escape of the Martian atmosphere and the loss of surface water were firmly influenced by solar activities. Tianwen-1 provided a unique chance to depict the solar wind streams between Earth and Mars during the minimum of Solar Cycle 25. During the three-month cruise phase of Tianwen-1, the solar wind flows were successively observed at Earth, Tianwen-1, and Mars. After the field of view correction and noise reduction, the solar wind velocity and density measured by Tianwen-1 show good agreement with those at Earth and Mars. The results indicate that the performance of the ion analyzer onboard the Tianwen-1 orbiter is reliable and stable. It is worth looking forward to the joint observations of ion escape with other Mars probes in the following Martian years. [ABSTRACT FROM AUTHOR]

China’s first Mars probe Tianwen-1 has successfully landed on the southern Utopia Planitia of Mars on May 15, 2021. The Zhurong rover is first equipped with a full-polarimetric Mars Rover Penetrating Radar (FP-RoPeR) system, aiming to map the subsurface fine structure and to find the potential underground water ice. However, different from the previous water ice detection of orbital radar, the FP-RoPeR signals will be affected by the induced field rotation (IFR) if electromagnetic (EM) waves propagate through rough interfaces. Therefore, in this article, we assess the IFR effects from rough interfaces on the circular polarization ratio (CPR) response of FP-RoPeR data, which is a significant parameter for water ice detection. The theoretical computation and numerical validation indicate that the depth, the number of rough interfaces, and relative permittivity are three vital parameters that affect the IFR effects; depth plays a more important role than the other two for FP-RoPeR system. The CPR estimation result will be with greater error in the shallow region (0–1 m). The relative error in the region of depth greater than 1 m can be guaranteed to be under 10%. [ABSTRACT FROM AUTHOR]

One important scientific objective of China's first Mars mission (Tianwen‐1) is to investigate the martian surface soil characteristics and water‐ice distribution. Layered ejecta craters (LECs) on Mars are characterized by their fluidized ejecta deposits which have been interpreted to indicate volatiles in the substrate where the impact occurred. Thus, they have potential to serve as important planetary exploration sites/targets of geological significance. In this study, we estimated the absolute model ages (AMAs) of 68 LECs with diameters >4 km using the Context Camera (an instrument onboard the Mars Reconnaissance Obiter, MRO) images in the two candidate landing areas of Tianwen‐1 mission, aiming to reveal temporal‐spatial variation of the regional subsurface volatiles, in particular water ice. The results from a combination of the derived AMAs and the ejecta mobility (EM) values for the southern Utopia‐Isidis Planitia (SUIP) and southern Chryse Planitia (SCP) show that the LECs in both regions plausibly have formed throughout the Amazonian and Hesperian periods. However, the subsurface volatile concentrations might have undergone different evolution histories: SUIP shows a relatively stable trend with time, while there seems a general downward trend in SCP. The presence of the fresh ∼1.5‐km‐diameter LECs suggests that volatile concentrations might have been at depth less than 150 m. We conclude with a discussion of recommendations for Tianwen‐1 and future explorations that have the ability to effectively detect any signs of past and present water/ice on Mars, which contain a wealth of information of past and recent climate. Plain Language Summary: China's first mission to Mars (Tianwen‐1) was launched on July 23, 2020 and successfully landed on the martian surface on 15th May 2021. Two martian surface areas were pre‐selected as the potential landing sites of the mission's rover (Zhurong). To understand the regional geology in detail, we carried out an extensive investigation of a total of 68 layered ejecta craters (LECs) in both sites: the southern Utopia‐Isidis Planitia and southern Chryse Planitia. A comprehensive analysis of LECs can provide key information of the structure and composition of the target substrate, subsurface volatile conditions, and their temporal variation, in particular for water ice. Using the technique of the crater size‐frequency distribution measurements, these LECs are dated to have formed during the Amazonian and Hesperian epochs. The two regions might have undergone different evolution histories: subsurface volatile concentration depth of the former shows a relatively stable trend over time, while the latter appears to exhibit a general downward trend with time. The smallest observed diameters of LECs suggest that volatiles may have been at depths of hundreds of meters, even ∼150 m. Both orbiter and rover radar payloads onboard Tianwen‐1 would significantly help to detect potentially habitable environments in the subsurface. Key Points: Crater counting is performed to derive model ages of the layered ejecta craters (LECs) in the two candidate landing areas of Tianwen‐1 missionThe LECs likely have formed throughout the Amazonian and Hesperian periodsThe subsurface volatile concentrations in both regions might have followed different evolution lines [ABSTRACT FROM AUTHOR]

As a hyperspectral imager aboard the orbiter "HX-1" of China's first Mars mission, the Mars Mineralogical Spectrometer (MMS) is designed with hyperspectral and multispectral operation modes to survey the mineral types and their distribution on the surface of Mars, and to study the overall chemical composition and evolution history of Mars. The multispectral modes of MMS are different from hyperspectral modes on the bands selection, spatial and spectral resolution, Signal-to-Noise Ratio (SNR) etc. So the spectral detection capability of each mode of MMS is also different. The ground validation experiment of MMS is conducted to evaluate the hyperspectral and multispectral data quality and detection capabilities. The main conclusions include: (1) The measured hyperspectra of typical mineral samples obtained by MMS agree well with the data acquired by the Standard Comparison Spectrometers (SCS) under the same measurement conditions, and the spectral uncertainty between MMS and SCS is less than 7% in the key spectral ranges (0.7 ∼ 2.2 μm ). For some typical minerals, the absorption band positions deviation between MMS and SCS are within 0.69 ∼ 14.86 nm , which are within the spectral resolution limits of MMS. (2) The six sets of band combinations designed for MMS multispectral modes are slightly superior to CRISM's multispectral mode in terms of spectral resolutions and bands selection, the water-containing minerals will be more accurately distinguished and identified, such as montmorillonite and kaolinite. Besides, the SNR of each multispectral mode is greater than 400 in the 500–2600 nm spectral range, which meets the requirements for the subtle spectral characteristics of water-containing minerals. (3) Benefiting from the MMS ground validation experiment and the experience of the OMEGA and CRISM, it is recommended that MMS first adopt the spatial continuous 52-sample or 104-sample (spatial resolution is about 0.53 ∼ 1.06 km ) multispectral operation mode for typical minerals global mapping and finding target areas of interest. Then the 208-sample multispectral mode (spatial resolution is about ∼ 265 m ) or 26-sample hyperspectral mode can be used to survey target areas of interest for the subtle mineral types characteristics and distribution. At last, 26-sample hyperspectral mode could be used to monitor the atmospheric composition of Mars by limb observations. [ABSTRACT FROM AUTHOR]

China's Mars rover Zhurong successfully landed on Mars on 15 May 2021, and it is currently conducting an exploration mission on the Red Planet. This paper develops slip estimation models for the Mars rover Zhurong based on the data drive approach. Data were obtained by Zhurong's validator ground indoor tests, and the test site was equipped with a low-gravity simulation device and simulated Mars soil to simulate the Mars conditions as much as possible. The obtained slip models trained by BP and GA-BP algorithms were applied to estimate Zhurong's longitudinal (slip_x) and lateral slip (slip_y) on Mars, and the slip estimation values were used to display Zhurong's actual driving path. The analyzed results prove that the GA-BP slip models perform better than the BP models, and can both be applied for correcting Zhurong's path. The proposed models have high potential in guiding the path planning and monitoring of the slip for the Mars rover Zhurong. [ABSTRACT FROM AUTHOR]

We used imaging, laser altimeter and thermal infrared data to map a 0.5 by 0.5° area containing the landing site of the Zhurong rover of the Tianwen‐1 mission. We analyzed the regional topography and thermophysical characteristics, and identified and characterized cones, impact craters, polygonal troughs, ridges and aeolian bedforms. An absolute model age of 757 ± 66 Ma was obtained for the major unit dominating the study area, younger than previous geological mapping results. We propose several targets of high scientific interest for Zhurong and a stratigraphic model composed of five layers (from bottom to top: Noachian basement, Early Hesperian volcanic ridged plains, Vastitas Borealis Formation materials, rocky materials and loose materials). The geomorphic features identified, the proposed stratigraphy and the regional geological evolution scenario set the stage for the Zhurong rover to continue to carry out its exploration of Mars. Plain Language Summary: Tianwen‐1 is China's first independent Mars mission. It consists of an orbiter and a lander and a rover (Zhurong). The Zhurong rover successfully touched down on the surface of Mars on May 15, 2021. The landing site lies in southern Utopia Planitia, in the northern lowlands of Mars. We identified various geomorphologic features within an area of 0.5 by 0.5° centered around the landing site of the Zhurong rover using image, elevation and temperature remote sensing data. We propose a history and geological evolution of the region to set the stage for the Zhurong rover exploration and analysis. Key Points: We conducted detailed geological mapping of the Zhurong landing region on MarsHigh scientific interest targets for Zhurong rover including cones, pitted‐wall craters, aeolian bedforms, polygons, and ridges are proposedA middle Amazonian surface age is suggested and a five‐layer stratigraphic model of the Zhurong landing region is proposed [ABSTRACT FROM AUTHOR]

The mobility system is an important part of the Mars rover and is one of the key subsystems for the Mars exploration mission. In this paper, the durability performance of China's Mars rover was tested and analyzed on the simulant Mars terrain. The total traveling distance of the rover for the durability test was 5,040 m, the test results showed that the average power consumption was 23.22 W, and the maximum power consumption was 75.9 W. The average power consumption of the rover increased linearly with the increase of the rover's velocity. Compared with the power consumption at 50 m/h , the power consumption at 100 and 200 m/h increased by 42.71% and 138.54%, respectively. The type of Mars terrain also has a great influence on the power consumption of the rover, the rover has the greatest resistance and the highest power consumption when driving on Terrain type D (Mars soil simulant + rocks), and wheel abrasion mainly occurred in this type of terrain. Finally, there were many scratches on the surface of the wheels, and a small amount of Mars soil simulant was deposited in the drum. However, the mobility performance of the rover did not decrease after traversing 5.04 km. The mobility system and the suspension are in good condition, and the motor and control system works well. [ABSTRACT FROM AUTHOR]

Mars Surface Composition Detector (MarSCoDe) is a scientific payload onboard the Mars rover of China's Tianwen-1 mission. With the capability of 1.6∼7 m remote detection and analysis, MarSCoDe instrument suite consists of a two dimensional pointing mirror and an optical head outside the rover cabin, a Laser Induced Breakdown Spectroscopy (LIBS) spectrometer and a Short Wave Infrared (SWIR) spectrometer collectively covering 240∼2400 nm and a master controller unit inside the rover body, calibration target sets, optical fibers and power cables connecting the internal and external units. Combining the techniques of active LIBS, passive SWIR and micro-imaging, MarSCoDe provides functions including elemental composition discrimination and quantitative determination, classification of rock and soil characteristics, sample texture imaging and characterization of plasma-excited area. This paper introduces MarSCoDe mainly in terms of scientific objectives, design requirements, assembly and implementation, spectral and radiation calibration, and performance verification. The LIBS laser irradiance on the target can soundly exceed 10 MW/mm2, and the performance of the LIBS module operated at different temperatures has been tested. The field of view of the SWIR spectrometer is 36.5 mrad. The micro-imager can extract the central pixel area of 320 × 320 and 1024 × 1024, and the former is binned into 64 × 64. The 2D pointing mirror has a wide forward detection range and a narrow backward calibration range, with the pointing pitch accuracy better than 0.133°. [ABSTRACT FROM AUTHOR]

Objectives: The Chinese Mars probe has been successfully launched and is currently orbiting Mars. This article analyzes several different satellite orbit characteristics in detail to find out the suitable orbits with stable operation characteristics. Methods: This paper uses the MAGREAS （Mars gravity recovery and analysis software/system） independently developed by Wuhan University to analyze the evolution of satellite orbits under different initial orbit heights, different initial orbital inclinations, different initial orbital eccentricities, and different orders of Martian gravitational field models. Then we make orbit predictions for the four situations.Results: The results show that satellite can run for nearly two years without any orbital adjustment. When the initial orbital inclination is 90°, it does not contribute to the running time of the satellite. In the calculation of orbital integration, the Martian gravity field model can be intercepted to 100 degrees without affecting the calculation accuracy.Conclusions: This paper has done a lot of orbit predictions based on different initial orbit elements, and analyzed the evolution characteristics of different satellite orbits. This research can provide a certain reference for China's Mars exploration project. [ABSTRACT FROM AUTHOR]

China's first Mars exploration mission (HuoXing-1) has been named as 'Tianwen-1' meaning Heaven Inquiry. Tianwen-1 was launched on July 23, 2020. In this paper, the scientific objectives of earlier and current Mars exploration missions worldwide are reviewed, and the scientific objectives, payloads and preliminary scientific investigation plan of China's first Mars exploration mission are introduced, and expected scientific achievements are analyzed. [ABSTRACT FROM AUTHOR]

This paper presents our efforts to characterize the candidate landing region (109°–133°E, 23°–30°N) for Tianwen‐1, China's first mission to Mars, in terms of engineering safety and scientific significance. Topographic analysis reveals that the region has a low elevation around −4,230 m, and 98% of the region have slopes smaller than 8°. The geomorphological mapping and analysis show that the region has an average crater density of about 28 craters (≥200 m in diameter) per 100 square kilometers, with several clusters of high crater densities distributed around the center of the region. There are also pitted cones distributed mainly in the southern part of the region, with a density of approximately 6.6 cones per 100 square kilometers in specific local areas. The region has rock abundances ranging from 1% to 23%, with local clusters of low and high rock abundances. The region comprises four main geological units, including a lowland unit formed in the Late Hesperian and a volcanic unit formed in the Amazonian and Hesperian period. Their specific surface ages are estimated through the analysis of crater size‐frequency distribution. Combining the engineering constraints on surface slopes, crater density, cone density, and rock abundance, a hazard map of the candidate landing region is generated for landing site evaluation and safety assessment. Based on the results, we further discuss the potential scientific outcomes from the exploration in this region. The findings will be helpful for the mission planning and maximization of the scientific return from Tianwen‐1, and complement existing Martian scientific research. Key Points: Topographic, geomorphological, and geologic characterization of the candidate landing region of Tianwen‐1A hazard map of the region combining engineering constraints on slopes, crater density, cone density, and rock abundanceTwo local areas in the region are highlighted as potential landing sites for their low hazard and scientific significance [ABSTRACT FROM AUTHOR]

The High-Resolution Imaging Camera (HiRIC) is one major payload of China's first Mars exploration mission, and its main objective is to obtain the detailed observation images of the key areas on the Martian surface. In this paper, the leading group of HiRIC shows a full blueprint of the HiRIC. The HiRIC can achieve a high resolution (0.5 m at an altitude of 265 km) with a wide swath width of 9 km. The HiRIC adopts an Off-Axis Three-Mirror Astigmatic (TMA) optical system with a focal length of 4640 mm, an F-number of 12 and a Field of View (FOV) of 2° × 0.693°. In order to reduce the instrument weight, carbon-based material is widely used in the opto-mechanical structure which is in ultra-lightweight design, thus, a light-weight camera with a total mass of 42 kg is obtained. The Time Delay and Integration (TDI) Charge Coupled Devices (CCDs) and Complementary Metal-Oxide-Semiconductor Transistor (CMOS) detectors are all set on the imaging plane to achieve the push-broom imaging and frame imaging, respectively. And the high Signal-to-Noise Ratio (SNR) >100:1 can achieve in multi observation types for various scientific imaging tasks. After 4-year design and fabricate, the HiRIC has been assembly. The testing results show that the instrument is in good condition, and the Modulation Transfer Function (MTF) can achieve 0.18 at Nyquist frequency. The HiRIC can achieve a well image on China first Mars exploration mission. [ABSTRACT FROM AUTHOR]

The Mars Mineralogical Spectrometer (MMS) is a hyperspectral imager onboard the Mars orbiter of Tianwen-1, China's first Mars exploration mission. MMS consists of 4 subassemblies: an Optical Sensor Unit (OSU), an Electronics Unit (EU), a Calibration Unit (CU), and a Thermal Control Accessories (TCA). With a 0.5 mrad IFOV and a 416-sample cell array for nadir observation, MMS can map the spectral and spatial information of the Martian surface through push-broom scanning, and it can transmit scientific data by hyperspectral mode or multispectral imaging mode through spatial and spectral combination. MMS can perform multi-sample hyperspectral imaging at full spectral resolution (0.379–1.076 μm with 2.73 nm/band, 1.033–3.425 μm at 7.5 nm/band, both spectral ranges at 2.1 km/pixel at 265 km). For the wavelength region of interest, the multispectral mapping mode provides additional options, a subset of 72 bands that are binned to minimum pixel footprints of 265 m/pixel. The major objective of the MMS is to analyze the compositions and distributions of the minerals on Martian surface, in order to characterize its evolution. [ABSTRACT FROM AUTHOR]

About every 26 months, the distance between Earth and Mars reaches a minimum, and that is the best time window for Mars exploration from Earth. In July 2020, three spacecraft started their journey to Mars: the Hope orbiter of the United Arab Emirates, the Tianwen-1 mission of China and the Perseverance rover of the United States' National Aeronautics and Space Administration (NASA). If all go well, these spacecraft will reach Martian orbit in February 2021 and start their scientific observations. Tianwen-1 is China's first mission to Mars. It includes an orbiter, a lander and a rover. It carries 13 scientific payloads and will investigate the topography, soil composition, water-ice distribution, internal structure, atmospheric environment and physical fields (electromagnetic and gravitational) of Mars. In this interview, we talked with the mission's Chief Scientist Yongxin Pan (潘永信) and Scientific Payload Sub-System Director Chi Wang (王赤) about this scientific mission and China's future plans for Mars exploration. [ABSTRACT FROM AUTHOR]

This paper describes the scientific objectives and payloads of Tianwen-1, China's first exploration mission to Mars. An orbiter, carrying a lander and a rover, lifted-off in July 2020 for a journey to Mars where it should arrive in February 2021. A suite of 13 scientific payloads, for in-situ and remote sensing, autonomously commanded by integrated payload controllers and mounted on the orbiter and the rover will study the magnetosphere and ionosphere of Mars and the relation with the solar wind, the atmosphere, surface and subsurface of the planet, looking at the topography, composition and structure and in particular for subsurface ice. The mission will also investigate Mars climate history. It is expected that Tianwen-1 will contribute significantly to advance our scientific knowledge of Mars. [ABSTRACT FROM AUTHOR]

China launched Tianwen-1 spacecraft successfully on July 23rd, 2020. The Mars Orbiter Subsurface Investigation Radar (MOSIR) is a subsurface radar sounder as a scientific instrument onboard Tianwen-1 orbiter. It is designed to study the compositions of Martian surface material, subsurface structure, and the ionosphere's total electron content. It can also perform passive observations in a transfer orbit to Mars. The subsurface stratigraphic structure is critical to the study on Mars geological and climatic evolution history. Considering the optimal tradeoff between penetrating depth and range resolution, MOSIR operates at low-frequency and high-frequency channels, with the frequency bands of 10–15 MHz or 15–20 MHz and 30–50 MHz, respectively. MOSIR provides a penetration depth of more than 100 m with a vertical resolution of 7.5 m (20 MHz bandwidth) and 30 m (5 MHz bandwidth) in free space. The range and azimuth focusing techniques are applied in ground data processing to achieve the resolution of several hundred meters (along-track) and several thousand meters (cross-track). MOSIR is intended to search for water ice and liquid water that may be associated with signs of life in the polar layered deposits, Tianwen-1 landing site, and other selected areas. [ABSTRACT FROM AUTHOR]

• Mars rover wheels' driving performance is obtained especially when complete skid. • The influence of large load on driving performance indices is studied. • The radial, axial, torsion, and deflection stiffness of Mars wheel are obtained. • The wheel ribs affect driving performance by reducing sinkage and drawbar pull. The soft ground and stones on the surface of Mars may cause sinkage of and damage to the wheels of a Mars rover. Therefore, we analyzed the performance of a wheel-step Mars rover from the perspective of terramechanics and structural mechanics. Using China's Mars rover wheel prototype and wheel-soil interaction testbed, we obtained the driving performance of the wheels of a Mars rover under various conditions, including full skidding conditions. The vertical load set in the tests was determined using the gravity of Mars and the mass of the wheel-step Mars rover. The results indicate that the driving torque, sinkage, and resistance coefficient have a linear relationship with the wheel vertical load. An analysis of the structural mechanical characteristics of the wheel of the Mars rover was conducted by testing the radial, axial, torsional, and deflection stiffness. We found that the wheel ribs can improve the stiffness of the wheel but may reduce its driving performance. The analysis methods and evaluation indices can be used to analyze the performance of the wheels of other Mars rovers. Furthermore, the findings of this study can be used to optimize wheel design and motion control of wheel-step Mars exploration rovers. [ABSTRACT FROM AUTHOR]

China's first Mars exploration mission (Tianwen‐1), launched on July 23, 2020 with the goal of "orbiting, landing, and roving," and its tentative landing areas (TLAs) are Chryse Planitia (TLA 1) and Isidis‐Elysium Planitia (TLA 2). Dust storm is a typical activity on Mars; it has strong interaction with atmospheric circulation and will influence the visibility of the Martian surface. To ensure the safety and accuracy for landing, it is meaningful to analyze the probability of dust storm activity during Entry‐Descent‐Landing (EDL) season in TLAs. First, based on Mars Orbiter Camera (MOC) and Mars Color Imager (MARCI) Daily Global Maps (MDGMs) from Mars Years 24–31, we identified 882 dust storms within the 2,000 km radius monitor circle of TLA 2 (short for TLA 2‐C). Second, the average daily probability of dust storm activity (Adp_ds) in TLA 2‐C was calculated, with a range of 0% to 14.13% showing obvious seasonality and discontinuity. Third, we divided TLA 2‐C into 0.5° longitude × 0.5° latitude square grids and calculated their spatial probability of dust storm activity. The spatial probability of dust storm in TLA 2‐C ranged from 0% to 11.87% and generally reduced from north to south. Finally, according to the temporal and spatial dust storm probability in TLA 2 during EDL season, we suggested the optimal landing time of China's Tianwen‐1 mission was in Ls = 20–41° and selected five preferred landing areas with the spatial probability of dust storm <3% for this mission. Plain Language Summary: The first China's Mars exploration mission (Tianwen‐1), will achieve the targets of "orbiting, landing, and roving." There are two tentative landing areas (TLAs) in the latitude range of 5–30°, Chryse Planitia (TLA 1) and Isidis‐Elysium Planitia (TLA 2). TLA 2 is on the south of Utopia which is an important origination area of dust storm sequences in the northern hemisphere. The probability of dust storm activity is an important criterion of atmospheric risk assessment for a Martian surface mission. Thus, it is crucial to evaluate the probabilities and characteristics of dust storm activity in and around TLA 2. In this paper, we used Mars Daily Global Maps (MDGMs) of Mars Orbiter Camera (MOC) and Mars Color Imager (MARCI) to (1) identify and catalog the dust storms in and around TLA 2; (2) calculate and analyze the temporal and spatial probability of dust storms in and around TLA 2; and (3) select the preferred landing time and areas for Tianwen‐1 mission based on the temporal and spatial probability of dust storm activity in TLA 2. Key Points: The temporal probability of dust storm activity in Isidis‐Elysium Planitia shows obvious seasonal and inconsecutive activityThe spatial probability of dust storm activity in Isidis‐Elysium Planitia is generally reduced from north to southThe optimal landing time was in Ls = 20–41°, and five preferred landing areas were selected for Tianwen‐1 [ABSTRACT FROM AUTHOR]

In this study, systematic conodont biostratigraphy and cyclostratigraphy are carried out on Ordovician sections from the North China and South China blocks. The Liangjiashan section, situated on the North China Block margin, accumulated shallow marine carbonate during the Early Ordovician. The Huanghuachang section (GSSP for the Dapingian Stage), situated on the South China Block margin, accumulated thinly bedded carbonates and minor clastics in a deep shelf environment. Conodont biostratigraphy and 405-kyr long-eccentricity cycles interpreted from the Liangjiashan and Huanghuachang sections are used to establish an Astronomical Time Scale (ATS) for the Early–Middle Ordovician period. The ATS indicates that the duration of the Floian Stage is 7.08 ± 0.405 Myr. The temporal ranges of Lower–Middle Ordovician conodont biozones are also estimated: the durations of the Serratognathus bilobatus , Serratognathus extensus , Oepikodus communis , Oepikodus evae , and Baltoniodus triangularis zones are 1.0 Myr, 5.1 Myr, 0.2 Myr, 0.8 Myr, and 0.2 Myr, respectively. The evolution of the ratio of obliquity to total power and short-eccentricity power to total power depicts periodicities of 1 Myr for the s 4 – s 3 term, and 1.9 Myr shifting to 1 Myr for the g 4 – g 3 term. The shift in the g 4 – g 3 term may indicate a chaotic transition in the Mars and Earth orbital motions from a (s 4 – s 3)–2(g 4 – g 3) to (s 4 – s 3)–(g 4 – g 3) resonance state during the Early Ordovician. • Early-middle Ordovician conodont and cyclostratigraphy of China are analyzed. • Liangjiashan and Huanghuachang sections span the late Tremadocian to early Dapingian. • Ca concentration series shows Milankovitch signature adjusted for tidal dissipation. • 405-kyr eccentricity cycles indicate 7.08 ± 0.405 Myr duration for the Floian Stage. • An Earth-Mars chaotic transition took place from the late Tremadocian to Floian. [ABSTRACT FROM AUTHOR]

The morphometric characteristics of the Kaidu River and Keriya River in the extremely arid Tarim Basin, and the Evros Vallis on Mars were compared to study the formation of the dendritic Evros Vallis, which has great significance for exploring ancient climate of Mars. The following results were obtained: (a) the average sinuosities of Kaidu River, Keriya River, and Evros Vallis are 1.17, 1.35, and 1.32 respectively. (b) the average bifurcation ratios are 3.84, 4.73 and 3.43 respectively. (c) the average stream length ratios are 2.21, 3.86 and 2.08 respectively. (d) the stream frequencies are 0.017, 0.028 and 0.002 respectively. (e) the drainage densities are 0.195 km−1 and 0.217 km−1, and 0.048 km−1 respectively. (f) the stream gradients are 3.74‰, 7.03‰ and 1.63‰ respectively. (g) the stream fractal dimensions are 1.70, 1.0 and 1.68 respectively. Paleodischarge estimations at different stream segments of Evros Vallis support the hypothesis that the V-bend area that joints the eastern and western segments possibly has a tectonic origin. Geomorphological evidence (e.g., tributaries) from high-resolution images and stream morphometric parameters from a comparative analysis (e.g., concave upward longitudinal profile and stream fractal dimension) support previous hypothesis that Evros Vallis is a mature drainage system formed by precipitation-driven surface runoff. This drainage process occurred either in a continuously warm-wet climate that lasted long enough on early Mars or in regional hydrologic cycles consisting of precipitation and occasionally returned runoff in intermittently clement climates. • Kaidu River and Keriya River in arid Tarim Basin were chosen as terrestrial analogs for the dendritic Evros Vallis on Mars. • Morphometric parameters of stream networks, e.g., sinuosity, bifurcation ratio, etc., are calculated and compared. • Martian Evros Vallis is a mature drainage system formed by precipitation-driven surface runoff. [ABSTRACT FROM AUTHOR]

• China's Zhurong rover explored four crescent-shaped TARs during the first 107 sols. • The crust formed by accumulation and induration of aeolian dust makes TARs light-toned in orbiter images. • Two TARs degraded into smaller megaripples due to a change of wind regime. • TARs might share similar formation and evolution mechanisms with megaripples. Aeolian bedforms are the signatures of wind interaction with unconsolidated, granular surface materials. Transverse aeolian ridges (TARs) are widely distributed on Mars but their formation remains enigmatic. China's Zhurong rover explored four crescent-shaped TARs, with two horns generally facing south, during the first 107 sols in southern Utopia Planitia, Mars. Rover images show that these bedforms have distinct light and dark variations on their surfaces that likely result from the combination of a bimodal distribution of particle sizes and the crust formed by the accumulation of aeolian dust. Two of these bedforms exhibit erosional forms on their west sides, where megaripples facing in a direction different from that of the crescentic bedforms they disrupt were created by more recent winds from the northeast. Differing erosional configurations of each of these bedforms in close proximity to each other are probably related to the angle between the bedform crest and the wind direction, and may further suggest that erosion of TARs starts from their two flanks. Secondary ridges of TARs widely recognized on Mars could be megaripples formed during this erosion process. At the Zhurong landing site, TARs degraded into megaripples, suggesting that they might share similar formation and evolution mechanisms there and elsewhere on Mars. [ABSTRACT FROM AUTHOR]

• TARs in the Zhurong rover landing area could be categorized as megaripples. • The formation or the last active period of the TARs could be as recent as 1 Ma ago. • The prevailing northerly wind has not changed notably since TARs formed. • Forked TARs might form after a long enough time under modern wind conditions. The enigmatic transverse aeolian ridges (TARs), with distinct morphology and albedo, are among the key geological features investigated by China's Tianwen-1 Zhurong rover on southern Utopia Planitia, Mars. Their morphologies and morphometrics are investigated through high-resolution imaging science experiment (HiRISE) orthoimage and Digital Terrain Model (DTM) products. A total of 5089 TARs are identified, with barchan TARs being predominant (97.6%). Morphometric analysis shows these TARs to be small and symmetrical aeolian landforms, with an average crest–ridge lengths of 33.9 ± 20.5 m, profile widths of 9.4 ± 3.8 m, profile heights of 0.4 ± 0.4 m, profile-height-width ratios of 0.04 ± 0.02, and profile symmetry ratios of −0.01 ± 0.13. In-situ observations from the Navigation and Terrain Camera (NaTeCam) show the crests of the TARs to be dark and sharp, while the flanks are interlaced by dark and bright materials. Close-up Multispectral Camera (MSCam) images reveal the TARs to be coated by granules of ∼1.5 mm in diameter. Given the morphometric characteristics and the presence of coating granules, the TARs in the landing area could be categorized as megaripples. Buffered crater counting (BCC) technique-derived absolute model age (AMA) reveals the formation time, or the last active period of the TARs, could be as recent as 1 Ma in the Late Amazonian. The morphometrics and direction of the horns of the barchan TARs suggest the winds for the formation of TARs blew mostly from the north. During the spring-summer transition period (Ls: 50°–93°), the Mars Climate Station (MCS) had recorded local bimodal winds in the landing area, with the speed of the northerly wind in the afternoon being a little stronger than the speed of the southerly wind in the morning. These observations are consistent with the wind fields described in the Mars Climate Database (MCD), which imply the northerly winds during the northern winter season to be responsible for the net sediment transport to the south. Two TARs observed in-situ with secondary NW-SE trending crest-ridges indicate that forked TARs might form given sufficient time (i.e., in the order of millions of years) under modern wind conditions, i.e., the TARs may be currently reworked, if only extremely weakly. [ABSTRACT FROM AUTHOR]

As an in-situ and stand-off detection technique, laser-induced breakdown spectroscopy (LIBS) can perform efficient geochemical sample identification and classification with chemometrics, and therefore LIBS has played a shining role in planetary exploration missions. Unlike in laboratory experiments, the LIBS sampling distance in field detection for planetary exploration naturally varies. The considerable spectral differences caused by the varying distance can be a critical challenge for chemometrics model training and testing. In this research, we address this issue by focusing on the construction of a chemometrics model with powerful learning ability rather than the conventional spectral data processing for distance correction. Specifically, we have investigated the performance of a designed deep convolutional neural network (CNN) on datasets consisting of multi-distance spectra. More than 18,000 LIBS spectra were collected by a duplicate model of the MarSCoDe instrument for China's Tianwen-1 Mars mission, at eight different distances ranging from 2.0 m to 5.0 m. These spectra were acquired from 39 geochemical standard samples, which were classified by the deep CNN. The competence of the CNN is compared with that of four alternative chemometrics, i. e. back-propagation neural network, support vector machine, linear discriminant analysis, and logistic regression. The CNN can surpass the other four algorithms in terms of overall prediction accuracy. In addition, we have inspected the dependence of the CNN performance on the distance number involved in the training set and the data properties of the testing set. Furthermore, it has been revealed that the CNN model can behave even better if an extremely simple distance correction procedure is supplemented. Our results show that CNN is an extraordinary chemometrics for material classification on multi-distance spectra datasets, implying that CNN-LIBS is a promising methodology for geochemical sample identification/classification in Tianwen-1 mission and other future planetary exploration missions, and in even more field detection scenarios with varying sampling distance. [Display omitted] • A chemometrics-focused solution to the LIBS distance effect issue has been proposed. • A deep CNN was designed to classify geochemical samples on multi-distance spectra. • The CNN surpasses four other methods (BPNN, SVM, LDA and LR) in overall accuracy. • The CNN can behave even better if a very simple distance correction is supplemented. [ABSTRACT FROM AUTHOR]