Photocatalytic Reactions of Desert Varnish, The

Johnson, Lacie
Numerous studies have been conducted on desert varnish over the years, yet there have been few advances in the field during the past decade. Currently the prevailing idea is biological processes create desert varnish, but there is little evidence to give this idea a solid foundation. This research will show that while desert varnish may or may not be created biologically, it plays a biological role far beyond creating desert varnish via the photo catalytic properties of semiconducting minerals that occur in the varnish. Light absorption by the varnish, leads to solar energy generation in a form that can be used by the non-phototrophic microorganisms associated with varnish. The experiments with desert varnish lead to the idea that desert varnish is photo-active. When desert varnish is illuminated by sunlight, reactions occur creating measurable changes in the composition of aqueous solution in contact with the varnish. The energy from the light creates electron hole pairs on the desert varnish. The electrons then reduce ferro- and manganese-oxides, while the holes oxidize other molecules (e.g., water, chloride). This research can support new areas of inquiry involving the chemical evolution of early Earth, the history of Mars, and even advances in solar cell technologies.
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