The Moon’s far side looks different because its surface has fewer broad, dark volcanic plains called maria and more heavily cratered highlands. A major part of the explanation is that the crust is thicker on average on the far side, making it harder for ancient magma to reach the surface and fill impact basins. Scientists are still investigating why the two hemispheres developed so differently.
The far side is not permanently dark
The Moon rotates once in about the same time it takes to orbit Earth, so the same hemisphere generally faces us. The far side still receives sunlight during its lunar day. “Far side” describes which hemisphere faces away from Earth, not a side that never sees the Sun. [1]
The near side has more maria
The dark patches visible from Earth are maria: large impact basins that were later flooded by basaltic lava. The far side has fewer of these broad lava plains and more bright, rugged highlands covered by ancient craters. Both hemispheres were struck by impacts; later volcanic resurfacing made the near side look smoother in many areas. [2]
Crust thickness is part of the explanation
NASA’s lunar measurements show that the Moon’s crust is thicker on the far side on average than on the near side. A thicker crust can make it more difficult for magma to break through and create extensive maria. The contrast is not explained by one simple wall that blocked every impact or eruption; geology, crust structure and the Moon’s early thermal history all matter. [3]
Scientists are still investigating the asymmetry
Researchers continue to test ideas about how the Moon formed and cooled, including why its crust became uneven. New gravity, topography and seismic measurements help refine the picture. The far side is familiar from spacecraft images, but its different geology remains an active scientific question.
Sources and evidence
- NASA — Moon Composition ↗
NASA overview of lunar crust, composition and the difference between the near and far sides.
- NASA — First Photo of the Lunar Farside ↗
Describes the far side’s cratered highlands and relative lack of large maria.
- NASA — Map of the Moon’s Crust ↗
Crust-thickness map derived from GRAIL gravity and Lunar Reconnaissance Orbiter topography data.
Sources consulted: 14 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Initial publication; open questions about the Moon’s hemispheric asymmetry are identified as unresolved.