How salts affect mud mobility at low pressures: implications for Mars and other extraterrestrial bodies

Abstract Sedimentary volcanism is a widespread geological phenomenon on Earth. Similar processes are theorized to occur on extraterrestrial bodies like Mars, potentially representing surface expressions of subsurface liquid water reservoirs. Recognizing extraterrestrial mud volcanism relies on identifying emplaced mud flow features based on their morphological characteristics. Despite the ubiquitous presence of salts on planetary surfaces, it remains unclear how different types of dissolved salts in mud mixtures may influence the behavior of erupted mud. This study integrates laboratory experiments, thermodynamic calculations, and rheometry measurements to investigate how concentrations of NaCl, MgSO4, Na2SO4, and CaSO4 affect such behavior. The results show that 10 wt.% MgSO4 and only 2.5 wt.% NaCl maximizes mud propagation, producing ropy patterns and narrow flows, while higher salt concentrations result in sheet-like flows covering wider areas. When the mud is supersaturated, the liquid state is prolonged but propagation is reduced. These findings reveal that mud salinity variations in low-pressure environments have a powerful effect on mud flow behavior. Improved understanding of such parameters is crucial for investigating the mudflows on extraterrestrial bodies, and the study of salt-enriched muds may be therefore crucial for unraveling Mars' geological evolution and its potential for harboring signs of ancient life.