As part of the Tianwen-1 mission, the Zhurong rover successfully touched down in southern Utopia Planitia on 15 May 2021. On the basis of the new sub-metre-resolution images from the High Resolution Imaging Camera on board the Tianwen-1 orbiter, we determined that the Zhurong rover landed at 109.925° E, 25.066° N at an elevation of −4,099.4 m. The landing site is near the highland–lowland boundary1 and multiple suspected shorelines2–7. Under the guidance of the remote sensing survey, the Zhurong rover is travelling south for specific in situ investigation. Supported by the six payloads on board the rover8, its initial key targets are rocks, rocky fields, transverse aeolian ridges and subsurface structures along the path. Extended investigation will aim at troughs and cones in the distance. A better understanding of the formation mechanisms of these targets may shed light on the historical volcanism and water/ice activities within the landing area, as well as the activities of the wind. These results may reveal the characteristics and evolution of the ancient Martian environment and advance the exploration of the habitability of ancient Mars.

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China's first Mars rover, Zhurong, successfully landed in southern Utopia Planitia on the Martian surface (Figure 1) on 15 May 2021. Zhurong was onboard the Tianwen-1 probe, which was successfully launched on 23 July 2020; the probe entered the Martian orbit on 10 February 2021 and released the Zhurong rover for landing about 3 hr before its touchdown (Li et al., 2021;Wan et al., 2020;Wu et al., 2021). The Zhurong rover landing represents the tenth in situ investigation of the Martian surface and the first in the lowland area of southern Utopia Planitia. Using the scientific payloads onboard the Zhurong rover (Li et al., 2021), including the Navigation and Terrain Camera (NaTeCam), Multispectral Camera (MSCam), Mars Surface Composition Detector (MarSCoDe), Mars Rover Penetrating Radar (RoPeR), Mars Rover Magnetometer, and Mars Climate Station, the Zhurong rover will investigate the topography, soil structure and geology of the roving area and the physical characteristics of the atmosphere. The rover will also analyze elements, minerals and rock types and search for signatures of water or ice in the roving area (Li et al., 2021;Zou et al., 2021).The landing site selection process for Zhurong included several stages. In the first stage, a global search process was conducted on the Martian surface to identify suitable regions that met the engineering constraints, including adequate solar illumination for generating power and warmth, lower elevation for a thicker atmosphere and longer deceleration time, and a flat terrain surface for safer landing (Dong et al., 2019;Wu et al., 2021). Three

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.

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Inverse synthetic aperture radar (ISAR) imaging of maneuvering targets via matching pursuit (MP) can produce high resolution and remove sidelobe effect, providing that the target rotation rate is already known. For non-cooperative uniformly rotating targets, the rotation rate is unknown and should be retrieved together with the ISAR image. In this paper, a computational efficient parametric MP is proposed to simultaneously retrieve the rotation rate and the high-resolution ISAR image. The joint estimation of ISAR image and rotation rate is converted into alternate independent estimations, i.e. alternately estimating the ISAR image and rotation rate in an iterative manner. With the iterations, the rotation rate estimate converges to the true value and meanwhile the clear ISAR image with high resolution and low sidelobes may be obtained. Numerical examples show that the approach is efficient in estimating the real target rotation rate and recovering the high resolution ISAR image.