2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014)

Paper No. 329-7
Presentation Time: 2:45 PM

NEW CONSTRAINTS ON THE RECURRENCE, GROWTH AND FADING CHARACTERISTICS OF LOW-ALBEDO STREAKS ON MARTIAN SLOPES AND THEIR POSSIBLE HYDROLOGIC IMPLICATIONS


MUSHKIN, Amit1, STILLMAN, David E.2, GILLESPIE, Alan R.1, MONTGOMERY, David R.1, SCHREIBER, B. Charlotte3 and HIBBITTS, Charles A.4, (1)Department of Earth & Space Sciences, University of Washington, Seattle, WA 98195, (2)Dept. of Space Studies, Southwest Research Institute, 1050 Walnut St #300, Boulder, CO 80302, (3)Department of Earth & Space Sciences, University of Washington, Box 351310, Seattle, WA 98195, (4)Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Rd, Laurel, MD 20723, mushkin@u.washington.edu

Low-albedo down-slope streaks that form repeatedly within weekly time-scales and subsequently fade over seasonal to decadal periods are commonly observed in the tropical and mid-latitudes of Mars. ‘Dry’ mass-wasting processes vs. ‘wet’ modification of the surface by aqueous phases are the mechanisms typically considered to explain their formation. Recently, high frequency HiRISE image time-series of seasonal recurrence, incremental growth and fading of small (meter-decameter scale) slope streaks, also termed ‘recurring slope lineae’ (RSL), have been presented in support of a ‘wet’ origin likely associated with brine seepage. Here, we use CTX image time-series and demonstrate recurrence, incremental growth and fading not associated with dust deposition for decameter-kilometer scale slope-streaks near Olympus Mons and in Arabia Terra. These dynamic characteristics support the previous association of slope streaks with brine seepage based on the geomorphic and spectral relations between streaks and their surrounding unaffected slopes.

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.