11:00 AM - 1:00 PM
[MIS17-P03] Characterization of cavernous structures on rocks based on Earth's analogues and laboratory experiments: Implications for aqueous environments on Jezero crater lakes on early Mars
Keywords:Mars, tafoni, chemical weathering
Here, we perform field surveys and laboratory experiments aiming to characterize morphology of the cavernous structures of tafoni, potholes, and cavities formed by acidic alterations . In field surveys, we observed coastal cavernous structures in the Shimokita and Boso peninsulas, Japan. In laboratory experiments, we simulate acidic alterations of carbonate rocks by slow melting of H2SO4 frost on limestone at low temperatures. For both field and laboratory samples, we analyzed the morphology and number density of cavities via a common methodology by constructing three-dimensional structures.
Our results of field surveys show that tafoni and potholes can be distinguished based on morphology, with being higher number density with smaller cavities for tafoni than pothole. Our experimental results show that acidic alterations could generate cavernous structures on limestone via dissolution, bubbling, and deposition of sulfate minerals. Based on the Principal Component analysis, we suggest that these three types of cavities can be distinguished mainly by the number density and diameter of cavities. By applying our approach to cavernous structures on Jezero rocks, we find that they are categorized in terms of the number density and diameter as in between tafoni and cavities formed by acidic alterations. The size and number density of some cavernous structures on Jezero rocks seen to agree with those of carbonate rocks that repeatedly altered by H2SO4 fluids, although the shape of merged cavities of altered carbonate is inconsistent with that of Jezero rocks. On the other hand, if the cavernous structures of Jezero rocks, this suggests that early Jezero lake/oceanic water was saline. The size of cavernous structures of Jezero rocks is lower than that of tafoni; whereas, their number density tends to be higher than tafoni. This suggests that Jezero’s cavernous structures might be tafoni formed in shorter periods than Earth’s, implying short-lived lakes on Jezero Crater.