Yutong Shi

• Xia, Miaosen; Zhao, Jiannan; Shi, Yutong; Lan, Qin; Wueller, Lukas & Hiesinger, Harald [Vis alle 7 forfattere av denne artikkelen] (2024). Prolonged Fluvial Activity Revealed by Mapping and Analyses of Valley Networks in the Northwestern Hellas Region, Mars. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 129(12). doi: 10.1029/2024je008601. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Valley networks (VNs) on Mars are crucial for understanding the Martian hydrologic and climatic history. However, the limited resolution of remote sensing data hindered the complete identification of Martian VNs, affecting our understanding of the formation and duration of VNs as well as their climatic significance. In this study, we utilized high‐resolution imaging and topographic data to conduct detailed mapping and investigations of the VNs around the northwestern margin of the Hellas basin, the largest impact basin and major sedimentary sink in the Martian southern highlands. We identified a total of 911 VNs with a cumulative length of 32,086.3 km, more than twice that of previous mapping results. Additionally, we analyzed the morphological parameters of VNs, including stream order, sinuosity, junction angle, stream slope, etc., investigated their geomorphologic characteristics, and determined their formation ages. We propose that occasional precipitation and regional groundwater fostered the formation of well‐developed VNs and a “Hellas Ocean” in the Noachian Period. The main fluvial activity occurred during ∼3.9–3.2 Ga. Subsequently, the climate transitioned from warm and semiarid to cold and arid during the Noachian‐Hesperian transition, leading to the evaporation of the “Hellas Ocean.” In the Amazonian, some small simple valleys formed during ∼2.1–1.0 Ga with the supply of meltwater associated with obliquity‐controlled glacial processes. These results reveal prolonged fluvial activity in the northwestern Hellas region with diverse water sources under changing climatic conditions, which make the region a very promising candidate for future in situ exploration missions.

• Shi, Yutong; Zhao, Siyuan; Karunatillake, Suniti; Cousin, Agnes; Zhao, Jiannan & Xiao, Long (2024). Sorting and Weathering Trends of Soil at Gale Crater, Mars: Implications for Regional Pedological Processes. Journal of Geophysical Research (JGR): Planets. ISSN 2169-9097. 129(12). doi: 10.1029/2024je008598. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Detailed soil characterization at Gale crater based on in situ observations has revealed compositional trends within soils, while the physical and chemical processes underlying the compositional trends remain to be evaluated. Here we use the grain‐morphometrical and geochemical trends across the Wentworth‐classes of 48 in situ soil targets at Gale crater to evaluate underlying pedological processes and potential chemical weathering signatures. The concentration of olivine minerals within the ∼250 to ∼500 μm size range indicates the prevalence of heavy mineral sorting in a granulometric sense in Gale soils that surpasses the possible effect of the cratering‐induced mixing processes. The extent of olivine sorting in soils varies spatially and is influenced by the targets' aeolian setting. The finest portion of Gale soils (<125 μm) is likely a mixture of allochthonous sediment, globally sourced from atmospheric suspension, and autochthonous counterparts from the weathering of local rocks, while the coarser soils (>125 μm) are mostly sourced from local rocks, with possible inputs from both the unaltered parent rock of the Stimson formation and the bedrocks that have undergone diagenetic alteration. If applicable globally, this would reinforce prior inferences that even dust‐mantled regions are geochemically heterogeneous owing to a substantial fraction of soils derived from underlying lithology. The low chemical weathering intensity and coupling of mobile elements in soils suggest localized, low pH and low water‐to‐rock ratio aqueous weathering conditions under predominantly cold and arid climates, which may occur either during post‐pedogenetic alteration in soils or during the acidic alteration of source rocks.

• Wang, Jiang; Zhao, Jiannan; Xiao, Long; Peng, Shuai; Zhang, Liang & Zhang, Zhixin [Vis alle 18 forfattere av denne artikkelen] (2023). Recent Aqueous Activity on Mars Evidenced by Transverse Aeolian Ridges in the Zhurong Exploration Region of Utopia Planitia. Geophysical Research Letters. ISSN 0094-8276. 50(6). doi: 10.1029/2022gl101650. Fulltekst i vitenarkiv Vis sammendrag

  Abstract 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.

• Xiao, Long; Huang, Jun; Kusky, Timothy; Head, James W; Zhao, Jiannan & Wang, Jiang [Vis alle 13 forfattere av denne artikkelen] (2023). Evidence for marine sedimentary rocks in Utopia Planitia: Zhurong rover observations. National Science Review. ISSN 2095-5138. 10(9). doi: 10.1093/nsr/nwad137. Fulltekst i vitenarkiv Vis sammendrag

  ABSTRACT Decades of research using remotely sensed data have extracted evidence for the presence of an ocean in the northern lowlands of Mars in the Hesperian (∼3.3 Ga), but these claims have remained controversial due to the lack of in situ analysis of the associated geologic unit, the Vastitas Borealis Formation (VBF). The Tianwen-1/Zhurong rover was targeted to land within the VBF near its southern margin and has traversed almost 2 km southward toward the interpreted shoreline. We report here on the first in situ analysis of the VBF that reveals sedimentary structures and features in surface rocks that suggest that the VBF was deposited in a marine environment, providing direct support for the existence of an ancient (Hesperian) ocean on Mars.

• Shi, Yutong; Zhao, Jiannan; Xiao, Long; Yang, Yong & Wang, Jiang (2022). An arid-semiarid climate during the Noachian-Hesperian transition in the Huygens region, Mars: Evidence from morphological studies of valley networks. Icarus (New York, N.Y. 1962). ISSN 0019-1035. 373, s. 114789–114789. doi: 10.1016/j.icarus.2021.114789. Fulltekst i vitenarkiv
• Shi, Yutong; Zhao, Jiannan & Wang, Jiang (2021). Gullies. I Bhardwaj, Anil (Red.), Planetary Science. World Scientific. ISSN 9789812836229. s. 275–291. doi: 10.1142/9789811224027_0008. Fulltekst i vitenarkiv
• Zhao, Jiannan; Xiao, Zijun; Huang, Jun; Head, James W.; Wang, Jiang & Shi, Yutong [Vis alle 8 forfattere av denne artikkelen] (2021). Geological Characteristics and Targets of High Scientific Interest in the Zhurong Landing Region on Mars. Geophysical Research Letters. ISSN 0094-8276. 48(20). doi: 10.1029/2021gl094903. Fulltekst i vitenarkiv Vis sammendrag

  Abstract 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.

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• Zhao, Jiannan; Shi, Yutong & Xiao, Long (2023). The Qaidam Basin as a Planetary Analog. Oxford University Press. ISBN 9780197851500. doi: 10.1093/acrefore/9780190647926.013.257. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Analog study is a convenient and effective way to understand the geomorphic features and geological processes of other planets. The Qaidam Basin, an intramontane basin in the northeastern Tibetan Plateau, northwest China, is a new and unique Mars analog study site. The basin hosts the highest and one of the driest deserts on the Earth, and its environment is characterized as cold, arid, of high altitude, of high UV radiation, and of high soil salinity. A variety of landforms that are comparable to those on the Martian surface have been identified, such as dunes, yardangs, valleys, gullies, lakes, and playas, providing opportunities to study the formation and evolution of similar Martian geomorphic features. Aqueous minerals including chlorides, sulfates, carbonates, and phyllosilicates are concentrated in the saline lakes and playas of the basin. Analog studies on the mineral assemblages of the Qaidam playas and Martian paleolakes and playas will help researchers better understand the hydrological environment and climate of the ancient Mars. The extreme environment of the Qaidam Basin also makes it an ideal site for astrobiological study. Detection of biomarkers and the isolation of microorganisms in the basin could provide clues for the search for life and a habitable environment on Mars. In addition, the accessibility of the Qaidam Basin makes the basin a potential testing ground for instruments and study methods to be used in future Mars missions.

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• Shi, Yutong; Zhao, Siyuan; Karunatillake, Suniti & Xiao, Long (2021). Semi-automated Image Segmenting Software for Martian Soil Granulometry. EGU General Assembly. doi: 10.5194/egusphere-egu21-7872. Fulltekst i vitenarkiv Vis sammendrag

  &lt;p&gt;Photoanalytical segmentation of individual soil grains and granulometry in high-resolution surface images are key in understanding sedimentation processes of planetary bodies before samples return to Earth. Here we present a Mathematica-based semi-automated image segmenting software tool that allows fast segmentation and granulometry analysis of Martian (soil) images based on the algorithm of Karunatillake et al. (2013, 2014), with a graphical user interface (GUI) to increase the software accessibility.&lt;/p&gt;&lt;p&gt;Our software has been adapted to Martian in-situ observation images including the Mars Hand Lens Imager (MAHLI) and Microscopic Imager (MI), providing segmenting and granulometry measurement through steps below: (1) Image imported: all common raster images are supported, as well as the IMG formatted MAHLI and MI images. While the MI image possesses a constant pixel size of 31 &amp;#956;m/pixel, for MAHLI images with various focal lengths, a focus motor count is required to calculate pixel size. The imported images are processed with gamma correction, contrast adjustment, background sharpen, and are visually decided whether there is a distinct foreground before going to the second step: (2) Image segmented: two independent modules are designed for segmenting the foreground and background with separate parameters, the coarser-grained foreground was masked before the finer-grained background is segmented. The GUI allows dynamic visualization of how the segmenting result changes with each parameter, facilitating the setting of parameters. (3) Granulometry: the grain size is calculated from the focal length and Wentworth classification of detected grains is established, highlighting the dominant class of grain size. The probability density and cumulative distribution of grain size can also be plotted. The granulometry results and parameters used are supported to export.&lt;/p&gt;&lt;p&gt;To check the performance of our software, we qualitatively tested our software with 57 MAHLI and MI images with or without foreground, with comparison to region based segmentation method such as BASEGRAIN, edge detection based method such as ENVI Classification tools and Feature Extraction tools, and supervised segmentation methods such as ENVI supervised classification tools and ImageJ Trainable Weka Segmentation tool. Our software shows better results in generating grains with closed boundaries and distinguishing adjacent grains with similar colors, with the fastest speed and less workload. Factors that may influence the accuracy of segmenting include image resolution, camera angle, inter-grain brightness/color contrast and shadow coverage.&lt;/p&gt;&lt;p&gt;In future work, a particle morphometry measuring function will be added so that statistics of grain roundness, sphericity, and angularity could be obtained. High-resolution images from the Moon and the asteroids will also be used in software testing to expand the range of its applicability to other planetary bodies. We will also consider its application on terrestrial cases, such as images of terrestrial sediments or petrological thin sections, which will need further improvement of the software concerning the increased compositional and optical complexity of terrestrial grains.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

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