The Soviet lunar and planetary exploration program in the 20th Century left a legacy of scientific results and new knowledge. It is difficult to remember how little we knew about the Moon and planets at the beginning of the space age in 1957, and how much we have learned as a result of sending out spacecraft. Table 21.1 provides a summary of the exploration milestones achieved by the Soviet program, most of which occurred during the first 15 years of the space age. Soviet scientists also made many scientific discoveries in the course of their missions. The early Luna missions established that whereas the near side of the Moon is dominated by the dark maria, the far side is dominated by the bright highlands, an interesting dichotomy that has yet to be adequately explained. Lunar mass concentrations were first discovered by Soviet spacecraft. Much of what we know of the atmosphere and surface of Venus comes from the Venera missions. 

二十世纪的苏联月球和行星探测计划为科学界留下了宝贵的遗产和丰富的知识。尽管有些记忆可能已经比较模糊，但事实上，在1957年，我们对月球和其它行星知之甚少，而在此后的时间里，通过发送航天器，我们积累了很多知识。在表21.1中，总结了苏联探测计划所取得的里程碑成就，其中大部分都是在太空时代前15年取得的。苏联科学家在其任务过程还完成了很多科学探索。通过早期的月球号任务确定：月球面对地球的一侧以暗月海为主，而背对地球的一侧则主要是亮高地。 这种现象很有趣，并且有待合理的解释。月球质量密集区最早是由苏联航天器发现的。我们所了解的关于大气和金星地表的大部分信息都来自金星号任务。