  Flowing water and brine have been proposed to cause seasonally reappearing
dark streaks called recurring slope lineae (RSL) on steep warm slopes on Mars,
along with other formation mechanisms that do not involve water. This study
aims to examine whether the evaporation of water vapor from the RSL, whether
from fresh water or brine, is detectable by observing water vapor and/or
clouds. In this study, we summarize the possible rate and duration of
water-vapor emission from RSL in different scenarios, simulate how the emitted
water vapor behaves in a global climate model, and discuss the detectability of
water vapor in nadir observations during existing and future explorations. We
found that, in typical cases, rapid horizontal dissipation within the planetary
boundary layer (PBL) following the release of water vapor prohibits cloud
formation and the excess water vapor from being distinguished from the
background with existing observations. Thus, we conclude that the lack of
correlation between the RSL activities and the overlying water-vapor column
density does not necessarily rule out the wet origin of RSL. Nevertheless, we
also found that water vapor tends to accumulate in basins and valleys in some
cases due to the combined effects of topography and low PBL; we suggest the
locations of such configuration as targets for future atmospheric studies of
Mars dedicated to quantifying water-vapor release (associated with RSL) to
elucidate the formation mechanism(s) of the RSL on the planet.

Earth and Planetary Astrophysics