ocr: d 19 Or A MARS: SENERAL INFORMATION MAMSS SATELLITES The polar caps Beside Mars's frozen subsoil, the planet has another reserve of water-its polar caps. The southern cap is subjected to high temperatures in summer and a long cold winter, so it expands and recedes with the seasons much more than the northern cap. In summer, its diameter does not exceed 350 kilometers, much smaller than its northern counterpart. Iti is even thought the southern cap disappeared entirely during the summer of 1969. In late winter, however, the southern cap spreads as far north as 50° latitude; by way of comparison ...
