Effective formation of surface flow due to salt precipitation within soils upon repeated brine seepages on Mars

On Mars, in the present and past, highly concentrated liquid brine is suggested to have formed repeatedly through ice melting and/or deliquescence. Such repeated seepages of brine could generate characteristic geomorphic features on Mars; however, the dynamics of repeated brine flows have been little investigated. Here we report results of laboratory experiments that investigate the flow behavior of brine (MgCl2 solution) upon repeated cycles of seepage and drying in glass beads on slopes. We compare the flow behavior with those of ultrapure water and ethylene glycol. We found that at a low flow rate, comparable to ice melting on Mars, both ultrapure water and ethylene glycol infiltrate radially into glass beads as infiltration flows. In contrast, even at a low flow rate, surface flows appear due to repeated seepages of MgCl2 solution. The surface flows move downward on slopes, forming elongated flow features. This happens because a decrease in the porosity and permeability of the glass beads caused by precipitated salts prevents infiltration in subsequent brine seepages. We suggest that precipitated salts have a role in the formation of transient surface flows on Mars, even at low seepage rates.

Automated summary

Highly concentrated liquid brine formed repeatedly through ice melting and/or deliquescence has the potential to generate characteristic geomorphic features on Mars. However, the dynamics of repeated brine flows have received little investigation. This study conducted laboratory experiments to investigate the flow behavior of brine upon repeated cycles of seepage and drying in glass beads on slopes. The results suggest that precipitated salts play a role in the formation of transient surface flows on Mars, even at low seepage rates.