A cold‐wet middle‐latitude environment on Mars during the Hesperian‐Amazonian transition: Evidence from northern Arabia valleys and paleolakes. Issue 9 (17th September 2016)

• Record Type: Journal Article
• Authors: Wilson, Sharon A.; Howard, Alan D.; Moore, Jeffrey M.; Grant, John A.
• Is Part Of: Journal of geophysical research. Volume 121:Issue 9(2016:Sep.)
• Page Start: 1667
• Page End: 1694
• Publication Date: 2016-09-17
• Subjects: Mars -- fluvial -- valleys -- paleolake -- climate -- Hesperian‐Amazonian; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2016JE005052
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: The growing inventory of post‐Noachian fluvial valleys may represent a late, widespread episode of aqueous activity on Mars, contrary to the paradigm that fluvial activity largely ceased around the Noachian‐Hesperian boundary. Fresh shallow valleys (FSVs) are widespread from ~30 to 45° in both hemispheres with a high concentration in northern Arabia Terra. Valleys in northern Arabia Terra characteristically start abruptly on steeper slopes and terminate in topographic depressions at elevations corresponding to model‐predicted lake levels. Longer valley systems flowed into and out of chains of paleolakes. Minimum discharges based on the dimensions of the incised channel assuming medium to coarse sand‐size grains ranges from tens to hundreds of m 3 s −1, respectively, consistent with formation via snowmelt from surface or sub‐ice flows. Hydrologic calculations indicate the valleys likely formed in hundreds of years or less, and crater statistics constrain the timing of fluvial activity to between the Hesperian and middle Amazonian. Several craters with channels extending radially outward supports evidence for overflow of interior crater lakes possibly fed by groundwater. Most FSVs occur away from young impact craters which make an association with impact processes improbable. The widespread occurrence of FSVs along with their similar morphology and shared modest state of degradation is consistent with most forming during a global interval of favorable climate, perhaps contemporaneous with alluvial fan formation in equatorial and midlatitudes. Evidence for a snowmelt‐based hydrology and considerable depths of water on the landscape in Arabia supports a cold, wet, and possibly habitable environment late in Martian history. Key Points: Valleys and paleolakes in northern Arabia Terra formed during a relatively short event in the Hesperian to middle Amazonian Fluvial valleys may represent a late, widespread episode of aqueous activity that was possibly contemporaneous with alluvial fan activity Snowmelt hydrology is consistent with a cold, wet, and possibly habitable environment that occurred late in Martian climate history