Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
On October 3, 1957, the Soviet (Russian) space probe Luna 3 flew around the far side of the moon and returned the first photographs ever seen of its hidden side. The biggest surprise was that the far side was very plain compared to the near side. The near side is covered with large dark lava plains, but the far side has almost none. The lave plains were first thought to be seas and are still given the Latin name mare (plural, maria) which means "sea." The maria are now known to be huge craters later flooded by lava. Only two large lava-filled craters were seen on the far side: a large one given the name Mare Muscoviense (Latin for Moscow Sea) and a smaller one named Tsiolkovsky after the Russian rocket pioneer Konstantin Tsiolkovsky. Almost no other craters are visible because the far side of the moon was fully sunlit and there were no shadows to reveal topography.
It is still not clear why one side of the moon was pummeled harder by the huge meteorites that created the maria basins. Since the maria are filled by dense lava flows, the earth's gravity caused that side of the Moon to face the earth as the Moon stopped rotating.
The view here shows Luna 3 passing the far side of the Moon. Features on the leftmost quarter of the Moon are visible from Earth; everything else is completely hidden from terrestrial viewers. The spacecraft took photographs on film, developed the film and scanned it on board, then sent the images back to earth. Digital imaging in 1959 was very crude compared to today, and the images are of poor quality compared to what we can achieve now. The original scene shows one of the photos as originally transmitted, and a composite of all the Luna 3 pictures processed using modern computer technology.
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Created 17 December 2007, Last Update 15 January 2020