Effective Formation of Surface Flow due to Salt Precipitation within
Soils upon Repeated Brine Seepages on Mars
Abstract
On Mars, in the present or 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.