Mars during the 1988 opposition



As far back as the 19th century the unmistakable orange-red color of Mars led to initial suppositions, since proven correct, that iron oxides must be dominant components of the martian surface soil and rock mineralogy. In September 1988 Mars passed within 59×106 km (37×106 miles) of Earth, affording ground-based astronomers their best view of the planet since 1971, and until 2001.

During this opposition, for the first time, high resolution spectral studies of Mars are being carried out at the University of Hawaii's 88-inch telescope atop Mauna Kea. These measurements are concentrating on the 0.3–1.0 (Am wavelength region, where numerous absorption features long known to be associated with Fe2+ and Fe3+ mineralogies occur.