Spectropolarimetry of Mars: the development of two polarization reversals

Mars was observed on 1995 March 11, 13 and 15 at phase angles 20-6,21-7and 22-G. K. Fox⋆ Space Astronomy Laboratory, 1150 University Avenue, University of Wisconsin, Madison, WI 53706, USAespectively, in the spectral range of 3200–10 500 Å using the UW-Madison, Pine Bluff Observatory spectropolarimeter. The observations show the development of two polarization reversals around 4600 and 8300 Å. The behaviour of the 4600-Å feature agrees well with previous observations and is a result of the presence of the Martian atmosphere. The presence of the 8300-Å feature is not anticipated from previous observations. It is shown that this feature can also be explained by the presence of an atmosphere.