Luna programme: The Soviet Union lands Lunokhod 1 on Mare Imbrium (Sea of Rains) on the Moon. This is the first roving remote-controlled robot to land on another world and is released by the orbiting Luna 17 spacecraft.

The Luna programme, occasionally called Lunik by western media, was a series of robotic spacecraft missions sent to the Moon by the Soviet Union between 1959 and 1976. The programme accomplished many firsts in space exploration, including first flyby of the Moon, first impact of the Moon and first photos of the far side of the Moon. Each mission was designed as either an orbiter or lander. They also performed many experiments, studying the Moon's chemical composition, gravity, temperature, and radiation.

Lunokhod 1, also known as Аппарат 8ЕЛ № 203 was the first robotic rover on the Moon and the first to freely move across the surface of an astronomical object beyond the Earth. Sent by the Soviet Union it was part of the robotic rovers Lunokhod program. The Luna 17 spacecraft carried Lunokhod 1 to the Moon in 1970. Lunokhod 0 (No.201), the previous and first attempt to land a rover, launched in February 1969 but failed to reach Earth orbit.

Mare Imbrium is a vast lava plain within the Imbrium Basin on the Moon and is one of the larger craters in the Solar System. The Imbrium Basin formed from the collision of a proto-planet during the Late Heavy Bombardment. Basaltic lava later flooded the giant crater to form the flat volcanic plain seen today. The basin's age has been estimated using uranium–lead dating methods to approximately 3.9 billion years ago, and the diameter of the impactor has been estimated to be 250 ± 25 km. The Moon's maria have fewer features than other areas of the Moon because molten lava pooled in the craters and formed a relatively smooth surface. Mare Imbrium is not as flat as it would have originally been when it first formed as a result of later events that have altered its surface.

The Moon is Earth's only natural satellite. It orbits around Earth at an average distance of 384,399 kilometres (238,854 mi); about 30 times Earth's diameter. Its orbital period and its rotation period are synchronized at 29.5 days by Earth's gravity pulling on the Moon. This makes the Moon tidally locked to Earth, always facing it with the same side. The Moon's gravitational pull produces tidal forces on Earth, which are the main driver of Earth's tides.