USSR reveals images from “dark side” of the Moon

On this day in 1959 the Soviet Union showed on national television the first pictures taken of the ‘dark side’ of the Moon (see below). The images were taken by the space probe Luna 3 some two weeks earlier. The initial batch of photographs included eighteen images good enough to resolve features on one third of the surface not seen from Earth. It later led to the first new lunar atlas in 100 years to contain new information (published by the USSR Academy of Sciences). Below is a stamp celebrating the probe’s achievement. The ‘dark side’, or far side of the Moon as its more accurately known, had intense interest for astronomers and planetary scientists. The most common belief before the photos came back was that it would appear similar to the side facing the Earth (commonly called the nearside). Instead, it turned out that the hemispheres’s have dramatic and distinctive differences between them. The near side is covered in lava flows (commonly called ‘maria’s or ‘seas’ as earlier astronomers thought they were water), making up 31.2% of the total visible surface. The far side looks more battered, has only 1% of it’s surface covered with maria’s, and has numerous craters. Moreover the crust is believed to be thinner on the near side, and more geologically active. This thinness in the crust doesn’t completely explain the differences between the hemisphere’s. Speculation has centered on whether another body collided with the Moon during its formation, or whether heat from the Earth melted the near side to explain its lopsided geology. You can read the latest research on the issue in this article “Making the Moon” which we published last year (http://dx.doi.org/10.1063/PT.3.2583) In any case, its geology makes the Moon one of the most unique objects in the solar system, and relatively close by for further exploration.

Date in History: 26 October 1959