Abstract
The Mars Exploration Rover Opportunity has investigated the landing
site in Eagle crater and the nearby plains within Meridiani Planum.
The soils consist of fine-grained basaltic sand and a surface tag
of hematite-rich spherules, spherule fragments, and other granules.
Wind ripples are common. Underlying the thin soil layer, and exposed
within small impact craters and troughs, are flat-lying sedimentary
rocks. These rocks are finely laminated, are rich in sulfur, and
contain abundant sulfate salts. Small-scale cross-lamination in some
locations provides evidence for deposition in flowing liquid water.
We interpret the rocks to be a mixture of chemical and silicictastic
sediments formed by episodic inundation by shallow surface water,
followed by evaporation, exposure, and desiccation. Hematite-rich
spherules are embedded in the rock and eroding from them. We interpret
these spherules to be concretions formed by postdepositional diagenesis,
again involving liquid water.
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