This further demonstration of the softness of the sulfate rock (or duricrust) raises questions over the NASA model for blueberry formation. As reported Nature, v428, p711-712, this involves deposion at the edge of a acid-saline lake, burial to 1 km (to allow conversion of goethite to hematite at 100C) and then exhumation by erosion. If the extent of the bluberry fields is as indicated by the Odyssey TEMs data, this exhumation has produced an enormous plain with a soft rock at the top. In my experience, soft rocks provide the erosional layer and hard rocks form the exposed platform. In addition, evidence of layered sulfate rich matrial was seen at Viking 1 and the Nature article reports OMEGA is reporting extensive sulfate deposits at Valles Marineris. Have all these buried and exhumed? IMHO the NASA model is not tenable and the origin of the sulfate + blueberries must be sought in a more recent, global-scale, event such as a major volcanic eruption or meteorite impact. Unfortunately all are not related to water.
And as a final query, if the sulfate rocks are soft and easily wind eroded, as shown by Nick, what value can be placed on the "bedding planes" identified at Eagle Crater?