Characterization of the seasonal variation of the Martian south polar cap with new observation data obtained by Tianwen-1 probe

China’s Tianwan-1 orbiter has recently observed the Martian South Polar Seasonal Cap (SPSC) around Ls =210°-332° in MY36 and obtained a bunch of data. The SPSC plays a crucial role in the planet's atmospheric dynamics, with its seasonal variation reflecting the Martian climate system. Although the recession of the SPSC has been observed over multiple Martian years, the asymmetry observed in this process makes it difficult to characterize. Understanding these asymmetries is essential for identifying time steps in the recession process and deepening our knowledge of Martian seasonal dynamics and climate cycles. Additionally, comparing the critical time steps of the recession process and investigating the impact of suspended dust on the SPSC will provide new insights into the relationship between the SPSC and climate, help in understanding the role of dust in shaping Martian atmospheric circulation, and offer valuable observational constraints for future climate models. In this study, we introduced a series of multi-temporal maps of the SPSC constructed from image data collected by the Moderate Resolution Imaging Camera (MoRIC) aboard the Tianwen-1 orbiter. With these maps, the dynamic changes (such as boundary, area, etc.) of the SPSC can be identified through remote sensing methods. And a dynamic recession model spanning from solar longitude (Ls) 210° to 332° would be demonstrated by incorporating a 5th-order polynomial fitting of the time-series on cap latitude. Furthermore, the influence of Martian dust activity on the SPSC during the spring and summer seasons could also be analyzed. This research could enhance our understanding of the complex interactions between Martian seasonal processes, dust activity, and the atmospheric system.