Small amounts of dissolved salts increase the mobility of mud flows on Mars and other extraterrestrial bodies

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. As we are currently missing ground truth, recognizing signs of extraterrestrial mud volcanism is based on comparative analysis with terrestrial mudflows. Despite the ubiquitous presence of salts on planetary surfaces, it remains unclear how different dissolved salts in mud mixtures influence the behavior of erupted mud. Our 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 in salt, the liquid state is prolonged but propagation is reduced. Hence, mud salinity has a significant influence on mud flow behavior in low-pressure environments, reflecting the balance between anti-freezing effects and viscosity-compositional effects. Our experimental results are limited to bentonite muds, yet the sensitivity to salt type/concentration is also expected for other muds, leading to a much broader range of morphology, longevity and spatial dispersion than previously assumed. Mud flow properties and spatial distribution are greatly influenced by salinity and composition in low pressure extraterrestrial environments such as Mars, according to a comparison of laboratory experiments, thermodynamic calculations, and rheometry measurements