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To accurately determine the chronological framework of climatic variations recorded by various Martian terrains, the absolute ages of Martian events and cratering rate need to be constrained by either in situ dating or returned samples. In situ K-Ar dating is currently a more plausible dating technique as compared with sample return. Jarosite (KFe3[SO4]2[OH]6) is the only confirmed K sulfate mineral that is widely present on Mars, as indicated by in situ detection, orbital remote sensing, and meteorite studies. Jarosite can be used for precise K-Ar and 40Ar/39Ar dating. The preservation of jarosite on Mars provides information about the nature and duration of aqueous processes on the Martian surface. Different ages of Martian jarosite represent the key to constraining the transition from Martian surface water activity to arid climatic conditions. This paper summarizes recent advances in our knowledge of the spatial distribution of Martian jarosite, its mineralogical properties and stability on Mars, the Ar diffusion kinetics of jarosite, and the current status of in situ K-Ar dating. Moreover, we examine the key scientific issues to be addressed for in situ K-Ar dating of jarosite and Martian sample return missions, and discuss future research directions. [ABSTRACT FROM AUTHOR]

On Earth, salt environments are the most relevant analogues to Martian salt deposits with regard to the search for preserved biomolecules. In this study, we analyzed the distribution of lipids in salt samples from Dalangtan and Qarhan in the Qaidam Basin, which is the most important area to carry out analog research of Mars in China. Furthermore, we compared the lipids distribution results with that from other typical Martian analog sites such as the Atacama Desert. Salt samples in the Qaidam Basin are enriched with fatty acid compounds, including normal fatty acids, unsaturated fatty acids, branched fatty acids, and acyclic isoprene acids. In addtion, glycerol dialkyl glycerol tetraethers (GDGTs) and archaeol compounds were also detected in these salt samples. Compared with the hypersaline samples, the clay samples not only have higher abuandance of fatty acids, GDGTs and archaeol compounds, but also a more diversed lipids composition. Only a few lipids were detected in the pure-saline samples, such as archaeol compounds. These clues suggest that content of salt minerals is the major factor affecting the distribution of lipids. This study provides an analogy for detecting and evaluating the traces of life that may exist on Mars. [ABSTRACT FROM AUTHOR]