China’s Mars rover, Zhurong, touched down on Utopia Planitia in the northern lowlands of Mars (109.925° E, 25.066° N) in May 2021, and has been conducting in situ investigations of the landing area in conjunction with the Tianwen-1 orbiter. Here we present surface properties derived from the Zhurong rover’s traverse during the first 60 sols of rover operations. Our analysis of the rover’s position from locomotion data and camera imagery over that time shows that the rover traversed 450.9 m southwards over a flat surface with mild wheel slippage. Soil parameters determined by terramechanics, which observes wheel–terrain interactions, indicate that the topsoil has high bearing strength and cohesion. The soil’s equivalent stiffness is estimated to range from 1,390 to 5,872 kPa per mN, and the internal friction angle ranges from 21° to 34° under a cohesion of 1.5 to 6 kPa. Aeolian bedforms in the area are primarily transverse aeolian ridges, indicating northeastern local wind directions. Surface rocks imaged by the rover cameras show evidence of physical weathering processes, such as wind erosion, and potential chemical weathering processes. Joint investigations utilizing the scientific payloads of the rover and the orbiter can provide insights into local aeolian and aqueous history, and the habitability evolution of the northern lowlands on Mars.
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The Tianwen-1 data used in this work are produced by the Beijing Aerospace Control Center (BACC). The data used in this manuscript are available at https://doi.org/10.11922/sciencedb.01425. The MOLA base map with geoid elevations is available at https://astrogeology.usgs.gov/search/map/Mars/GlobalSurveyor/MOLA/Mars_MGS_MOLA_DEM_mosaic_global_463m. Source data are provided with this paper.
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We thank all the scientists and engineers who contributed to the Tianwen-1 mission, in particular those from the China Academy of Space Technology (CAST), Shanghai Academy of Spaceflight Technology (SAST), Harbin Institute of Technology (HIT), Beijing Aerospace Control Center (BACC) and Chinese Academy of Sciences (CAS) for their dedicated work on the Zhurong Mars rover and Tianwen-1 mission. This work was supported in part by: the National Natural Science Foundation of China under Grant 51822502 (L.D.), Grant 91948202 (H.G.), Grant 61972020 (C.L.) and Grant 62003025 (Xiaoxue Wang); the Development Program of China under Grant 2019YFB1309500 (H.G.); the Fundamental Research Funds for the Central Universities under Grant FRFCU9803500621 (L.D.); the ‘111 Project’ under Grant BP0719002 (Z.D.); the Heilongjiang Postdoctoral Fund under Grant LBH-Z20136 (H.Y.); the Self-Planned Task of State Key Laboratory of Robotics and System (HIT) under Grant SKLRS202101A03 (H.Y.); and the Pre-research project on Civil Aerospace Technologies by CNSA under Grant D020102 (Y.Z.).
The authors declare no competing interests.
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a, The group photo of Zhurong rover and Tianwen-1 lander on the Martian surface. The rover dimensions are 2.6 × 3.0 × 1.85 m when fully unfolded, and its mass is 240 kg. The image was taken by a Wi-Fi camera deployed by Zhurong on sol 18 (1 June 2021). Image credit: CNSA/BACC. b, Six scientific payloads, hazard avoidance cameras and the grouser wheel on the Zhurong rover. The six scientific payloads2 include NaTeCam3, Multispectral Camera (MSCam), Mars Rover Penetrating Radar (RoPeR)4, Mars surface Composition Detector (MarSCoDe)7, Mars Rover Magnetometer (RoMAG)6, and Mars Climate Station (MCS)5. Two pairs of hazard avoidance cameras (HazCam), of engineering payloads, are configured forward and backward for stereo observation. The grouser wheel is evenly arranged with 20 grousers on its outer surface and spokes inside. c, Creeping and crabbing modes of the Zhurong rover implemented by taking advantage of the rocker-bogie suspension with active joints46. The creeping mode of Zhurong to get out of sunk and climb steep slopes is realized by decreasing or increasing the angle of the main rocker arm, coordinated with the movement of other wheels. The crabbing mode of Zhurong for lateral movement is achieved by turning the steering wheels at 90° and driving laterally.
a, MOLA-derived elevation map of the Tianwen-1 surrounding region in a circular shape. The 20 km diameter circular map is centered at 109.925° E, 24.980° N, about 10 km south of the Tianwen-1 landing site. b, The slope map of the Tianwen-1 surrounding region is based on the MOLA data (baseline 926 m). (The upper layer is a portion of the MOLA shaded-relief topographic map of Mars, which is available at https://astrogeology.usgs.gov/search/map/Mars/GlobalSurveyor/MOLA/Mars_MGS_MOLA_DEM_mosaic_global_463m ; the base map is a 5 m pixel–1 global mosaic of Mars using imagery acquired by the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO), which is available at http://murray-lab.caltech.edu/.).
The simulation of four traverses after the rover driving off the ramp is visualized. The yellow line represents the planned path, and the blue line represents the path obtained in the simulation. The movement sequence of the rover is carried out in the order of the number marked. The terrain map (DEM covered with orthophoto) is built from NaTeCam images.
a, Stagged pattern of the wheel track left by a wheel moving with longitudinal slip. b, Wheel track extraction and wheel slip ratio analysis over a traverse to waypoint A. Eight continuous track units are extracted on the orthograph for local wheel slip ratio calculation. The image was taken by the NaTeCam on sol 11. c, d, f, show wheel tracks and the associated wheel sinkage. Images were taken by the rear HazCam. c, A part of the discernable wheel track with well-trimmed edges. The wheel sinkage is estimated to be about 10 mm. d, Most typical form of wheel tracks without well-trimmed edges. Its wheel sinkage is estimated to be ~5 mm. e, Near-Side view of the wheel-terrain interaction. Only wheel grousers are submerged into the soil and the wheel rims of these three right wheels are millimetres above the surface. Some soil adhered to the wheel surface or on the groove bordering the grousers. This image was taken by the Wi-Fi camera on sol 12 when the rover was retreating. f, shows both wheel tracks interrupted by gravels and wheel tracks with rim sinking below the surface. The wheel sinkage of the wheel tracks interrupted by gravels is estimated to be ~2 mm. The wheel sinkage of wheel tracks formed by the wheel rim sinking below the surface is estimated to be ~15 mm. Image credit: CNSA/BACC.
a, The distribution of the mapped craters (diameters > 1 m) in the circular region surrounding the Tianwen-1 landing site, overlaid on the HiRISE image (ESP_069665_2055). C1, C2, C3 are three large craters (diameter > 200 m) in this area. The circular region is centred on 109.925° E, 25.048° N with a diameter of 4 km, and its centre is 1 km south of the Tianwen1 landing site. b, A log-log plot of the incremental sizefrequency distribution of craters. The diameter interval is √2D m and the crater diameter refers to the middle value of each bin. c, A degraded crater with smooth rims imaged by NaTeCam on sol 60 (13 July 2021). d, A crater almost fully filled with sand imaged by NaTeCam on sol 23 (6 June 2021). Image credit: CNSA/BACC.
a, b, c, are diverse rocks observed by Zhurong rover on the surface. These rocks appear irregular in shapes and have darktoned interiors covered with light-toned soil or dust on the surface. Image credit: CNSA/BACC.
a, Force diagram for the wheel-soil interaction of a grouser, rigid wheel. b, Characteristics curve of the driving torque and the motor current for the driving motor on the Zhurong rover.
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Ding, L., Zhou, R., Yu, T. et al. Surface characteristics of the Zhurong Mars rover traverse at Utopia Planitia. Nat. Geosci. 15, 171–176 (2022). https://doi.org/10.1038/s41561-022-00905-6