Post by Dr. Jonathan Clarke

Soon after landing at Meridiani Planum the Opportunity rover imaged some curious wind erosion features. These were the haematite concretions commonly known as “blueberries” standing out from the substrate on stalks up to a cm or so in length. Good examples were seen at Eagle Crater, others were imaged at Fram Crater (Image 1). In places, the concretion has protected the underlying substrate from erosion. Sediments hosting the hematitic concretions have been eroded, leaving some concretions perched on small stalks. Several rocks at the Spirit landing site also show pedestals or fingers projecting away from rock surfaces.

Image 1: Two approximate true colour Pancam images of a boulder in Fram Crater, Meridiani Planum showing haematite concretions with a residual tail or stalk. The circular depression in the lower panel is from drilling by the RAT instrument. It is 45 mm in diameter. Top panel Sol085B_P2532_1. Credit: NASA/JPL/Cornell. Bottom panel image Sol088B_P2542_1. Credit: NASA/JPL/Cornell.

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