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Space/Science » in reply to Possible solution to the mystery of the Type 2 material on Mars?

Paper points to dry unweathered silica (glass)
dtb — (archived)

Read that abstract more carefully. They are specifically saying the OMEGA results are NOT consistent with water-weather lava, i.e., amorphous silicates like in clays.

They instead point to high-silica rocks like obsidian -- volcanic glass that is very, very dry. I imagine you'd also see similar spectral features from unweathered rhyolite, which is like obsidian but had a higher water content in the magma, leading to explosive eruptions and deposition as welded tuffs or pumice. Or maybe rhyolite doesn't work as even cryptocrystalline rocks would show the same IR signatures of crystaline vs amorphous Si.

Either way, that points to MAGMA that has interacted with water underground to enrich its silica content and to drive explosive volcanism, but not to weathering of the rocks by liquid water on the surface.

Be careful generalizing the Gusev "nodules" -- finding a highly localized 90% silica deposit is far more likely to suggest hydrothermal alternation than finding regional-scale formations with a somewhat enchanced silica content.

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