Some problems of the atmosphere of Mars from spectrophotometric observations in 1956

In 1956 there was observed a sharp decrease in the contrast of the details on the surface of Mars, while the general colour of the planet changed but little. The author concludes that the atmosphere of the planet became hazy only in the very lowest layers and that there were no essential changes in the general optical properties of the atmosphere itself. Spectrograms of the polar cap, made in the second half of September and at the beginning of October, showed that the polar cap is an atmospheric formation, formed by a condensation of the particles that cause the usual scattering in the upper layers of the planet's atmosphere.