Mariner 9 Ultraviolet Spectrometer experiment - Observations of ozone on Mars.

The Mariner 9 Ultraviolet Spectrometer has observed the 2550 A ozone spectral absorption feature on Mars. This absorption was previously detected in the south polar region by Mariner 7 in 1969. Mariner 9 did not observe ozone at any time in the equatorial region, nor at the south polar cap during its summer season. However, ozone was found in the north polar region beginning at a latitude of 45 deg N and extending northward. Ozone later appeared in the southern hemisphere southward of 50 deg S as the Mars autumnal equinox approached. The presence of ozone on Mars seems to be coupled to the water vapor content of its atmosphere.