The question of what the other side of the Moon looks like has captivated humanity for millennia because we only ever see one face of our nearest celestial neighbor. This led to the common, inaccurate phrase: the “dark side” of the Moon. Thanks to robotic exploration, we have known precisely what the unseen side looks like for decades. The side always hidden from Earth, accurately called the “far side,” is distinct in appearance and geology from the familiar face we observe nightly.
The Critical Difference Between “Dark Side” and “Far Side”
The popular term “dark side of the Moon” is a misconception that confuses visibility with illumination. Both the near side and the far side receive almost equal amounts of sunlight over the course of a lunar orbit. Because the Moon rotates on its axis, every part of its surface experiences about two weeks of daylight and two weeks of night, just like Earth.
The far side is fully illuminated by the Sun during the New Moon phase and is completely dark during the Full Moon. The accurate term, “far side,” refers to the hemisphere we never directly see. The original use of “dark” meant “unseen” or “unknown,” which caused the misunderstanding that the area was perpetually unlit.
The Mechanism of Synchronous Rotation
We only ever see one hemisphere of the Moon due to tidal locking, which results in synchronous rotation. Tidal locking occurs because of the gravitational interaction between the Earth and Moon. The Moon’s rotation period around its axis is exactly the same as the time it takes to complete one orbit around Earth, approximately 27.3 Earth days.
The Earth’s gravity created a slight elongation, or tidal bulge, on the Moon. The Earth’s pull on this bulge slowed the Moon’s rotation over billions of years until it reached equilibrium. In this tidally locked state, the Moon constantly rotates, but it keeps the same face pointed toward us. If the Moon did not rotate, we would see all sides of it as it circled Earth.
Because the Moon’s orbit is not perfectly circular, a slight “wobble” known as libration allows us to peek around the edges. This rocking motion means that observers on Earth can see about 59 percent of the Moon’s total surface over time. The remaining 41 percent of the surface remains permanently hidden from direct view.
The Age of Exploration: When We First Saw the Far Side
The question of what lay on the far side remained unanswered until the dawn of the space age. Humanity received its first glimpse of the unseen hemisphere in October 1959, achieved by the Soviet Union’s Luna 3 spacecraft. This was the first mission to successfully photograph the far side.
The probe passed the Moon and captured a series of low-resolution images of the Sun-lit far side. The Luna 3 mission covered about 70 percent of the far side’s surface, immediately dispelling the mystery of the hidden face. Later missions, including the Apollo program and the Lunar Reconnaissance Orbiter, have provided comprehensive, high-resolution maps of the entire region.
A World Apart: The Unique Appearance of the Far Side
The far side of the Moon presents a starkly different landscape from the near side, appearing more rugged and heavily cratered. The most striking difference is the near-total absence of maria, the large, dark plains of solidified ancient lava that dominate the familiar near side. While maria cover about 31 percent of the near side, they account for only about 1 percent of the far side’s surface.
This lack of dark plains makes the far side brighter and more reflective overall, as its surface is primarily composed of bright, ancient highlands. Geologists believe this dramatic difference, known as the lunar dichotomy, is linked to a much thicker crust on the far side. Data from the NASA Gravity Recovery and Interior Laboratory (GRAIL) mission suggests the far side’s crust is approximately 12 miles thicker than the near side’s.
One leading theory suggests that the Earth’s heat, when the Moon was young, caused the near side to remain warmer for longer. This warmth influenced the distribution of heat-producing elements and led to a softer, thinner crust on the near side, allowing magma to rise and form the extensive maria. The far side cooled more quickly and had a thicker crust, which prevented large-scale volcanic resurfacing. This left a landscape saturated with impact craters, including the immense South Pole–Aitken basin.