NEW CONSTRAINTS ON THE RECURRENCE, GROWTH AND FADING CHARACTERISTICS OF LOW-ALBEDO STREAKS ON MARTIAN SLOPES AND THEIR POSSIBLE HYDROLOGIC IMPLICATIONS
CRISM observations in multiple studies consistently indicate that darkened slope-streak surfaces are spectrally enriched in FeOx and are void of detectable water/ice spectral absorption bands. Thus, the brine seeps considered for slope streak formation are likely low-volume transient events that evaporate and/or freeze and sublime leaving behind a meta-stable dry precipitate that ‘stains’ the surface dark.
The geomorphic, spectral and dynamic characteristics of slope streaks appear to support the possible presence of pressurized sub-surface aquifers that may be released via faults or cracks that are able to produce recurring transient discharge events during favorably warm daily/seasonal surface conditions. Considering such a ‘wet’ mechanism, first-order calculations of the liquid volumes associated with the formation of the ~105-106 slope streaks on present-day Mars suggest the presence of regional-scale extensive aquifers and/or effective recharge mechanism for local-scale aquifers perhaps during high obliquity periods.