OMEGA spectra from White Rock and Meridiani Planum, Mars

OMEGA spectra from White Rock and Meridiani Planum, Mars
OMEGA spectra from White Rock and Meridiani Planum, Mars Each of the lines on this graph is a "spectrum," a plot of how reflective is a spot on Mars with increasing wavelength. The black line is a representative spectrum from White Rock itself. The green line represents the dark sand on the crater floor near White Rock. The blue line is an olivine-rich spectrum from Meridiani planum. The red line is a spectrum rich in iron and magnesium-bearing clay minerals from Meridiani Planum.

All the spectra bear similarities. They all have a strongly upward slope from 0.4 to 0.7 microns, the visible range, which gives all of them the overall red color that is common to Mars. All have a dip near 1 micron, indicating the presence of iron; the White Rock, crater floor, and mafic spectra also contain a much smaller dip near 2 microns, indicating that the iron and magnesium is found in a mineral called pyroxene. The clay spectrum has noticeable dips at 1.9 microns (indicating that water is bound in the chemical structure) and 2.3 microns (indicating the presence of hydroxyl, OH- groups, another signature of the presence of water). Although White Rock bears some similarity to the clay spectrum, it does not contain those two dips, so there is no clear evidence for the presence of water. Courtesy ESA / OMEGA / plot by Ryan Anderson