The physical exploration of the Moon began when Luna 2, a space probe launched by the Soviet Union, made a deliberate impact on the surface of the Moon on 14 September, 1959. Prior to that the only available means of lunar exploration had been observations from Earth. The invention of the optical telescope brought about the first leap in the quality of lunar observations. Galileo Galilei is generally credited as the first person to use a telescope for astronomical purposes, having made his own telescope in 1609. The mountains and craters on the lunar surface were among his first observations.
Human exploration of the Moon since Luna 2 has consisted of both crewed and uncrewed missions. NASA's Apollo program has been the only program to successfully land humans on the Moon, which it did six times on the near side in the late 20th century. The first human landing took place in 1969, when the Apollo 11 astronauts Buzz Aldrin and Neil Armstrong touched down on the surface in the region of Mare Tranquillitatis, leaving scientific instruments upon the mission's completion and returning lunar samples to Earth. All lunar missions had taken place on the lunar near side until the first soft landing on the far side of the Moon was made by the CNSA robotic spacecraft Chang'e 4 in early 2019, which successfully deployed the Yutu-2 robotic lunar rover. On 25 June 2024, CNSA's Chang'e 6 conducted the first lunar sample return from the far side of the Moon.
The goals of lunar exploration across all major space agencies focus on the continued survey of the lunar surface through lunar missions in preparation for the eventual establishment of permanent human outposts.
It is believed by some that the oldest cave paintings from up to 40,000 BP of bulls and geometric shapes, or 20–30,000-year-old tally sticks were used to observe the phases of the Moon, keeping time using the waxing and waning of the Moon's phases. Aspects of the Moon were identified and aggregated in lunar deities from prehistoric times and were eventually documented and put into symbols from the very first instances of writing in the 4th millennium BC.
One of the earliest known possible depictions of the Moon is a 3,000 BCE rock carving Orthostat 47 at Knowth, Ireland. The crescent depicting the Moon, as with the lunar deity Nanna/Sin, has been found from the 3rd millennium BCE.
The oldest named astronomer and poet, Enheduanna, Akkadian high priestess to the lunar deity Nanna/Sin and princess, daughter of Sargon the Great (c. 2334 – c. 2279 BCE), had the Moon tracked in her chambers. The oldest found and identified depiction of the Moon in an astronomical relation to other astronomical features is the Nebra sky disc from c. 1800–1600 BCE, depicting features like the Pleiades next to the Moon.
The ancient Greek philosopher Anaxagoras, whose non-religious view of the heavens was one cause for his imprisonment and eventual exile, reasoned that the Sun and Moon were both giant spherical rocks and that the latter reflected the light of the former. Plutarch, in his book On the Face in the Moon's Orb, suggested that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms. He also entertained the possibility that the Moon was inhabited. Aristarchus attempted to compute the Moon's size and distance from Earth, although his estimated distance of 20 times Earth's radius (which had been accurately determined by his contemporary Eratosthenes) proved to be about a third the actual average distance.
Chinese philosophers of the Han dynasty believed the Moon to be energy equated to qi but recognized that the light of the Moon was a reflection of the Sun. Mathematician and astrologer Jing Fang noted the sphericity of the Moon. Shen Kuo of the Song dynasty created an allegory equating the waxing and waning of the Moon to a round ball of reflective silver that, when doused with white powder and viewed from the side, would appear to be a crescent.
Indian astronomer Aryabhata stated in his fifth-century text Aryabhatiya that reflected sunlight is what causes the Moon to shine.
Persian astronomer Habash al-Hasib al-Marwazi conducted various observations at the Al-Shammisiyyah observatory in Baghdad between 825 and 835. Using these observations, he estimated the Moon's diameter as 3,037 km (equivalent to 1,519 km radius) and its distance from the Earth as 346,345 km (215,209 mi). In the 11th century, the Iraqi physicist Alhazen investigated moonlight through a number of experiments and observations, concluding it was a combination of the Moon's own light and the Moon's ability to absorb and emit sunlight.
By the Middle Ages, before the invention of the telescope, an increasing number of people began to recognize the Moon as a sphere, though many believed that it was "perfectly smooth".
Telescopic exploration before spaceflight
In 1609, Galileo Galilei drew one of the first telescopic drawings of the Moon in his book Sidereus Nuncius and noted that it was not smooth but had mountains and craters. Later in the 17th century, Giovanni Battista Riccioli and Francesco Maria Grimaldi drew a map of the Moon and gave many craters the names they still have. On maps, the dark parts of the Moon's surface were called maria (singular mare) or seas, and the light parts were called terrae or continents.
Thomas Harriot, as well as Galilei, drew the first telescopic representation of the Moon and observed it for several years. His drawings, however, remained unpublished. The first map of the Moon was made by the Belgian cosmographer and astronomer Michael van Langren in 1645. Two years later a much more influential effort was published by Johannes Hevelius. In 1647, Hevelius published Selenographia, the first treatise entirely devoted to the Moon. Hevelius's nomenclature, although used in Protestant countries until the eighteenth century, was replaced by the system published in 1651 by the Jesuit astronomer Giovanni Battista Riccioli, who gave the large naked-eye spots the names of seas and the telescopic spots (since called craters) the names of philosophers and astronomers.
In 1753, the Croatian Jesuit and astronomer Roger Joseph Boscovich discovered the absence of an atmosphere on the Moon. In 1824, Franz von Paula Gruithuisen explained the formation of craters as a result of meteorite strikes.
The since-disproven possibility that the Moon contains vegetation and is inhabited by selenites was seriously considered by major astronomers of the early modern period even into the first decades of the 19th century. In 1834–1836, Wilhelm Beer and Johann Heinrich Mädler published their four-volume Mappa Selenographica and the book Der Mond in 1837, which firmly established the conclusion that the Moon has no bodies of water nor any appreciable atmosphere.
The Cold War-inspired "space race" and "Moon race" between the Soviet Union and the United States of America accelerated with a focus on the Moon. This included many scientifically important firsts, such as the first photographs of the far side of the Moon in 1959 by the Soviet Union, and culminated with the landing of the first humans on the Moon in 1969, seen around the world as one of the pivotal events of the 20th century and human history.
The first artificial object to fly by the Moon was uncrewed Soviet probe Luna 1 on 4 January 1959, which went on to be the first probe to achieve a heliocentric orbit around the Sun. Luna 1 was designed to impact the surface of the Moon.