Martian Concretions--Or Are They?

The Martian spherules are concretions, said NASA in a press conference today. Also, dissolving crystals of something like gypsum left penny-shaped holes (vugs) in the sediment. The regolith is full of sulfur, notably the hydrated iron sulfate jarosite and the magnesium sulfate mineral kieserite. All these point to a groundwater-saturated regime in Meridiani Planum. Whether the site was actually under a sea or lake is not yet certain. Read more...