Analogue study of Polygonal surface structures in the Qaidam Basin and on Mars

Yanan Dang 1, Yi Xu1, Long Xiao1 ,2, Jiang Wang2
1Space Science Institute, Lunar and Planetary Science Laboratory, Macau University of Science and Technology, Macau, China, 2Planetary Science Institute, China University of Geosciences, Wuhan, China

Polygonal surface structure (PSS) is a very common landform on Earth and Mars, which has been observed and studied for many years. The formation and evolution of PSSs are strongly related to local environment and climate change. This work focuses on the characteristics and possible formation mechanisms of PSSs in the Qaidam Basin, which is a potential Mars analogue site because of its high UV radiation, extremely low precipitation, high evaporation and various aeolian geomorphologies. This study, the morphology of PSSs in the Qaidam Basin are described, categorized and compared to their counterparts on Mars. Their possible formation mechanism has also been proposed, which would help enhance our understanding of the origin and evolution of PSSs, and implications for climate change occurred on Mars.

We conducted the photography, topography measurements, samples collection and other field work in Qaidam Basin. The samples are used for analysis of mineral composition of PSSs region. Remote sensing data such as Google Earth images are applied to investigate the spatial distribution and classification of PSSs. For Mars, HiRISE data are used to locate and characterize the martian PSSs, while the CRISM data are used to identify the notable mineralogical criteria of the PSSs region.

The results indicate that the PSSs in Qaidam Basin are mainly distributed inside six playas named Dalangtan, Qahansilatu, Kunteyi, Mahai, Yiliping and Qarhan. Field investigation showed that all PSSs in the Qaidam Basin have a range in size from centimeters to hundreds of meters in diameter. The small-sized PSSs are commonly less than 10 m in diameter and display as triangle, quadrangle, and hexagon. Some of them are spatially arranged by aligning a line or assembled closely forming a honeycomb. The middle-sized PSSs (10-100 m) usually have discontinuous subdued borders. In some cases, small-sized polygons occur inside of them. The large-sized PSSs (100-300 m) have a border vary in size from 4 to 6 m wide and most of them have raised rims. The prominent rim defined polygons is probably good indicator of presence of playas. It has been suggested that there were many ancient salt lakes which had formed playas on Mars based on the occurrence of polygons and evaporate minerals. Almost all of these PSSs in the Qaidam Basin have counterparts on Mars. The variety occurrence of polygonal terrain in the Qaidam Basin would have undergone a series of stages evolution including drowning of layered salts, evaporative concentration, desiccation and wind erosion, which reveals a possible paleo-environment and subsequent environmental change on Mars.