THE reason for the extraordinary and sudden disappearance of the south polar cap on Mars during its perihelion opposition in 1956 due to outside influence, primarily that of solar activity, was considered at the time of the opposition¹. It is only now that two such series of processes as the exceptionally important solar activity on the Sun towards the end of August with a large flare on August 31, 1956, of the Y type, connected with the emission of cosmic and sub-cosmic radiation^{2â 5}, and the extraordinarily frequent occurrence of intensive dust storms after August 20 with the disappearance of the polar cap on Mars during August 31â September 1, 1956 (refs. 1, 6â 10), are being physically related.