Salt Triggered Melting of Permafrost in the Chaos Regions of Mars

Introduction: Mars surface bears traces of many fluvial-like features, geomorphic identified as outflow channels, valley networks etc. Among these a particular one stands above others from the dimensional point of view. Outflow channels bear unique water erosion characteristics, that led Baker and Milton (1974) [1] to believe that are caused by a surface runoff of large amounts of water, in short geological time. Water origin, necessary for these processes was the topic of many works. Among these theories one generally accepted idea considers that water is originating from melting of permafrost layers positioned in the places of today chaos'. Here is an investigation that takes into account the exoergic salt-ice dissolution reaction, along with freezing point depression of formed salty solutions, as a complentary or a stand-alone process in chaos-outflow channel formation mechanism. This model is trying to best fit the observation of Iani Chaos-Ares Vallis-Chryse Planitia system. Water source: Currently there are three more or less widely accepted ideas concerning the formation of outflow channels and the origin of water necessary for outflow " carving " : 1. Massive release of subsurface confined aquifer; first proposed by Carr [2]. Release of the aquifer water involves some catastrophic event (e.g. meteorite impact, faulting etc.) in such a manner that the groundwater should be released at surface through permafrost layer. 2. Dehydration of hydrates evaporites, having as caloric energy source volcanic activity of Tharsis [3]; evaporitic minerals present in source places for outflow channels, such as gypsum, epsomite, kieserite in the presence of a geothermal gradient would release the structural water at critical points specific for every mineral, hence all the water is structural water, implying huge amounts of evaporitic deposits being prior deposited. 3. Melting of permafrost ground ice. There are many morphologic evidences that the Martian soil bears large amounts of water trapped in ice form (permafrost). Ogawa et al. [4] pointed out that permafrost melting could be powered by the heat released from associated magmatic intrusions, that raise the thermal gradient around specific places, most of them being connected to Tharsis volcanic activity. Salt occurrences: Early evidences about the presence of sulfates on Mars dates back to Viking landers in 1976 [5]. X-ray fluorescence data collected, led to recognition of Mg-S, and latter to the concept that MgSO 4 class salts, could be the cementing agent in Martian soils at two widely separated landing places (Chryse Planitia and …