Sulfate-Rich Eolian and Wet Interdune Deposits, Erebus Crater, Meridiani Planum, Mars

Abstract

This study investigates three bedrock exposures at Erebus crater, an , 300 m diameter crater approximately 4 km south of Endurance crater on Mars. These outcrops, called Olympia, Payson, and Yavapai, provide additional evidence in support of the dune-interdune model proposed for the formation of the deposits at the Opportunity landing site in Meridiani Planum. There is evidence for greater involvement of liquid water in the Olympia outcrop exposures than was observed in Eagle or Endurance craters. The Olympia outcrop likely formed in a wet interdune and sand sheet environment. The facies observed within the Payson outcrop, which is likely stratigraphically above the Olympia outcrop, indicate that it was deposited in a damp-wet interdune, sand sheet, and eolian dune environment. The Yavapai outcrop, which likely stratigraphically overlies the Payson outcrop, indicates that it was deposited in primarily a sand sheet environment and also potentially in an eolian dune environment. These three outcrop exposures may indicate an overall drying-upward trend spanning the stratigraphic section from its base at the Olympia outcrop to its top at the Yavapai outcrop. This contrasts with the wetting-upward trend seen in Endurance and Eagle craters. Thus, the series of outcrops seen at Meridiani by Opportunity may constitute a full climatic cycle, evolving from dry to wet to dry conditions.

Large wind ripples on Mars: A record of atmospheric evolution

“…We note that in the absence of additional context (grain size and sedimentary structures like soft-sediment deformation and/or desiccation cracks), the interpretation of the small-scale trough cross-sets is non-unique because they could represent the signature of wind-drag ripples formed in a denser atmosphere. However, independent evidence suggesting wet depositional conditions supports the original interpretation (86,87). In contrast, later along its traverse, the Opportunity rover found ~10-20 cm-thick crosssets superimposed on high angle foresets on the south face of the Cape St Mary outcrop at Victoria crater (32) (Fig.…”

“…4) (27,86,87), which were interpreted as the signature of subaqueous ripples in a wet inter-dune environment. The fluvial hypothesis was favored to an eolian origin on the basis of (i) the three-dimensional geometry of the cross-sets, (ii) their scale, and (iii) their paleo-environmental context.…”

Recent developments in planetary Aeolian studies and their terrestrial analogs

“…1) that are at least a dozen meters in thickness Hayes et al, 2011), greatly expanding the stratigraphic thickness of the Aeolian sandstones seen earlier in Endurance crater (Grotzinger et al, 2005). Opportunity also found evidence of dunes with a strong sulfate signature (perhaps more the result of pore-filling materials than of the sand itself), with wet interdune areas, during exploration of Erebus crater (Metz et al, 2009). Hematite concretions within the sulfate-bearing sandstones are interpreted to indicate that a considerable flow of groundwater took place through the sandstones following their emplacement (Squyres et al, 2004a).…”

Source-to-Sink

“…The most detailed outcrop analysis of eolian cross-strata on Mars is for the Burns formation, as viewed by Opportunity in the Endurance Crater (Grotzinger et al 2005) and in the Erebus Crater (Metz et al 2009). Stratification types, especially the distinctive wind-ripple laminae, are clearly visible, as are reactivation surfaces and an interpreted super bounding surface (Wellington).…”