Spirit might find evaporites – minerals formed as water dries up. Salt or gypsum are familiar ones here on Earth. Salt's component parts – sodium and chloride – are separated, dissolved in sea water, but as the water dries up, the sodium and chloride join together to form the mineral halite. On Mars, Spirit might find evaporites like gypsum, or calcium magnesium sulfate. It might also find minerals involving carbonates (e.g., calcium carbonate). These are sometimes, although not always, produced by or from living organisms. But they are almost always a sign of water when found on Earth. Another sign will be in the way the sediments are organized. For example, if the sediments were blown in by winds, the layers may be more erratic, to reflect the changing directions of airflow (as in fossil dunes here on Earth). If they were deposited by water, they are more likely to be layered evenly, one on top of the other in rhythmic stacks. The most exciting result Spirit might find is that liquid water existed at the surface of this site for a long time because persistent standing bodies of water are possible habitats for life.
Within Gusev Crater lie the Columbia Hills.
Related categories MARS TOPICS
GEOLOGY AND PLANETARY SCIENCE
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