The reason for this difference between the two sides of the Moon is still not fully understood, but it seems that most of the dark lavas that flowed out to produce the maria formed under the Earth-facing half.

Several solar cells were mounted on the outside of the cylinder, and these provided electric power to the storage batteries inside the space probe.

[citation needed] Shutters for thermal control were positioned along the cylinder and opened to expose a radiating surface when the internal temperature exceeded 25 °C (298 K).

[citation needed] Its interior held the cameras and the photographic film processing system, radio transmitter, storage batteries, gyroscopic units, and circulating fans for temperature control.

Initial radio contact showed that the signal from the space probe was only about one-half as strong as expected, and the internal temperature was rising.

The space probe passed within 6,200 km of the Moon near its south pole at the closest lunar approach at 14:16 UT on 6 October 1959, and continued over the far side.

On 7 October, the photocell on the upper end of the space probe detected the sunlit far side of the Moon, and the photography sequence was started.

After the photography was complete the spacecraft resumed spinning, passed over the north pole of the Moon and returned towards the Earth.

After the mission was accomplished, and the probe made several orbits around the Earth, the secular rise in the eccentricity resulted in a decrease of the perigee because the semimajor axis is conserved.

After launch from the Baikonur Cosmodrome, Luna 3 passed behind the Moon from south to north and headed back to Earth.

The return orbit was calculated so that the spacecraft passed again over the Northern hemisphere where the Soviet ground stations were located.

The camera carried 40 frames of American-made temperature- and radiation-resistant 35mm isochrome film recovered by the Soviets from downed American Genetrix espionage balloons.

[20] In 1961, the first globe (1:13600000 scale)[21] containing lunar features invisible from the Earth was released in the USSR, based on images from Luna 3.

[22] Features that were named include Mare Moscoviense and craters called after Konstantin Tsiolkovsky, Jules Verne, Marie Curie and Thomas Edison.