Behavior of the Martian South Polar CAP 1986

The regression of the Martian south polar cap during the 1986 apparition is examined on the basis of Mars photographs obtained at the Bosscha and Hida Observatories. Before L_{s} = 230°, the size of the polar cap in 1986 appeared to have been similar to those in earlier years. In the period L_{s} = 240°--250°, the size of the south polar cap in 1986 seems to have been bigger than those in 1971 and 1977, which were bigger than those of normal years. However, in the period L_{s} = 240°--250°, it seems to have been a little smaller than that in 1939, the largest reported. The 1986 regression seems to have been one of the slowest in the period L_{s} = 240°--250°. Like the case of the north polar cap, the behavior of the south polar cap is different from year to year. The possibility of a correlation between the size of the south polar cap around L_{s} = 250° and the occurrence of global dust storms is also examined.