The geology of the terestrial planets / Геология планет земной группы

The flight of the Mariner 2 spacecraft past Venus in December 1962 marked the start of a new era in the exploration of the solar system. At that time our knowledge of the terrestrial planets other than Earth (Mercury, Venus, and Mars) was largely astronomical in nature. Centuries of telescopic observations had established the planets’ orbital motions very precisely, had determined their sizes and some of their rotational motions, but revealed almost nothing about their surfaces. Venus was completely shrouded in clouds; some vague markings had been seen on Mercury; and our perception of Mars was still colored by fanciful interpretations of its supposed canals. The Moon was the only object in the solar system, other than Earth, about whose geology we could informatively debate. By 1962 efforts were well underway to systematically decipher the geologic history of the Moon by application of stratigraphic techniques to interpretation of telescopic photographs and by comparison of lunar craters with terrestrial impact craters (Shoemaker, 1962; Shoemaker and Hackman, 1962). Even with the Moon, however, misconceptions were widespread. Lunar craters were still believed by many to be volcanic, and the Moon was commonly perceived as a primitive undifferentiated body which would yield unaltered samples of the materials from which the planets formed. <...>