Sulfates are abundant at the Martian surface, incorporating sulfur delivered by volcanic eruptions and degassing. The thickest sulfate accumulations are found in the interior layered deposits (ILDs) of Valles Marineris. The ILDs have been interpreted as either purely sedimentary deposits or weathered volcanic products. We performed nonlinear spectral unmixing of CRISM data located in the lower, massive member of the ILD pile in Ophir Chasma. The best spectral fit is obtained when primary igneous minerals (orthopyroxene, plagioclase) and coquimbite were present, alongside kieserite and szomolnokite, which were identified in previous ILD studies. Geomorphological evidence shows that the igneous minerals are from a source within the ILDs. Our findings suggest that the deposition of the lower member of the ILDs was influenced by Tharsis-related syntectonic and synvolcanic activity within the subsided Valles Marineris plateau, and by the redox state of an overlying Valles Marineris sea in a geologic context akin to volcanogenic massive sulfide deposition on Earth. Subsequent climate cooling, potentially related to Tharsis activity waning, would have led to gradual sea freezing, resulting in further alteration in acid-cold environment, and precipitation of the polyhydrated sulfates that compose the upper, layered ILD member. ILD erosion by glacial flows down to the currently exposed chasma floor level and aeolian erosion have shaped the current ILD morphology. In summary, the comprehensive ILD pile formed by in-situ weathering of volcanic products, redox state instabilities, and water level fluctuations in a warming and cooling Valles Marineris sea.

We develop a novel three-dimensional viscoelastic modeling method using an implicit finite difference scheme, while the properties of sparse and block matrices are utilized to make the solution of the method possible. The advantage of this method is that the introduction of implicit format makes it alleviate the numerical dispersion problem with the same accuracy and has better stability. In order to verify the validity and accuracy of the method, this paper elaborates its basic principles and analyzes the results through a series of forward simulations of simple models. In addition, we also gives an outlook on the direction of the subsequent refinement of the 3D viscoelastic implicit finite difference method as well as the potential application prospects.

Gullies are actively changing landforms on planet Mars. The prevailing hypothesis, supported by a suite of different studies, states that present-day activity in these gullies is caused by fluidised granular flows driven by the sublimation of seasonal CO2 ice. However, the long-term formation process of gully landscapes is a contentious issue as water-driven debris-flow processes could easily explain erosion. In contrast, we do not know if CO2-driven granular flows can cause a significant amount of erosion. In this study, we conducted flume experiments investigating the flow dynamics and erosion capacity of CO2-driven granular flows under different substrate and flow settings. Our experiments show that CO2-driven granular flows under Martian conditions are efficient erosive agents, which can erode and entrain large volumes of unconsolidated material in various environmental (i.e. substrate and flow) settings. In general, erosion and entrainment enhance the mobility of CO2-driven flows. However, the frost and thermal conditions of the slopes and the flow composition determine the erosion efficiency of these flows. Finally, based on terrestrial debris-flow erosion theory we estimate that collisional forces at the base of CO2-driven flows can cause erosion of the underlying bedrock or permafrost.