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Planetary Spectra


About the Spectra of the Planets and Satellites

The compiled data lists of spectra of the planets and their satellites comes from many investigations. The specific references to each piece of data can be found in the reference given with each spectrum. The spectra indicate the composition of the body. For example, the weak, broad absorptions in the lunar spectra near 1 and 2 microns indicate the mineral pyroxene, and the generally increasing trend is a result of the lunar glass. The Mercury spectrum is very similar to the Lunar highland spectrum (although other published spectra by Faith Villas do not show this absorption). Spectra of Mars show a rapid rise from the ultraviolet (0.35 micron) to the IR (1 micron), indicative of iron oxides and the red color of Mars. The absorption near 2 microns in the martian spectrum is indicative of the carbon dioxide in the martian atmosphere. The spectra of Jupiter and Saturn are dominated by many strong absorptions due to methane in the planet's atmospheres. Spectra of Uranus and Neptune, not included here (yet), also show strong methane absorption bands. Spectra of the Galilean satellite Io have an absorption near 4 microns indicative if sulfur dioxide, and a decreasing reflectance from the near IR (1 micron) to the UV (0.35 micron) similar to sulfur. Spectra of the Galilean satellites Europa , Ganymede, and Callisto are all dominated by water ice absorptions in the IR (1 to 4 microns). However, water ice (frost) appears white in the visible, but these spectra decrease from about 0.8 micron to the UV, and indicate some contaminants in the ice. Europa has the purest ice, next comes Ganymede, and then Callisto. The rings of Saturn are similar to the icy Galilean satellites in that they are dominated by water ice absorptions in the IR and some other, unidentified material, in the visible. Most of Saturn's satellites have spectra similar to Ganymede, with a similar interpretation, but the ice appears to be a little purer and with smaller grains than on Ganymede. A spectrum the Saturnian satellite Rhea is given as an example. The spectrum of Pluto is dominated by methane ice absorptions.

More spectra to be added

U.S. Geological Survey, a bureau of the U.S. Department of the Interior
This page URL= http://speclab.cr.usgs.gov/planetary.spectra/planetary-sp.html
This page is maintained by: Dr. Roger N. Clark rclark@speclab.cr.usgs.gov
Last modified November 18, 1998.