Martian south polar cap 1986

The regression of the Martian south polar cap for the 1986 apparition is examined with the measurements of the photographs of Mars obtained at the Bosscha Observatory and at the Hida Observatory. In the period Ls=240°-250°, the size of the south polar cap in 1986 seems to be bigger than that in 1971, but similar to that in 1939, which is bigger than those of other years. The case of the regression seems to be one of the biggest type in the period Ls=240°-250°. Like the case of the north polar cap, the behavior of the south polar cap is different from year to year.