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Ancient fingerprints in the clay

The thermodynamics of ancient clays on Mars seems inconsistent with the idea that a thick atmosphere of carbon dioxide caused a warm, wet era in the planet's early history. What did cause it remains an enigma.

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Figure 1: Subsurface smectites.


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Catling, D. Ancient fingerprints in the clay. Nature 448, 31–32 (2007).

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