Contents

MoonEdit

The Moon is Earth’s closest celestial neighbor and the largest natural satellite in the inner solar system relative to its planet. It profoundly shapes Earth’s tides, stabilizes the planet’s axial tilt, and has served as a testing ground for exploration, science, and national prestige. Its geologic record preserves a long history of solar system processes, including planetary formation, bombardment by debris, and volcanic activity that ceased billions of years ago. From the standpoint of policy and resource strategy, the Moon sits at the intersection of national interest, scientific inquiry, and the development of a more capable private space sector.

The Moon’s relationship with Earth is a defining feature of both bodies. It orbits Earth in an approximately circular path at a mean distance of about 384,400 kilometers, and is tidally locked, presenting the same face to Earth over every revolution. This geometry has allowed long-running observations from Earth and from orbiting spacecraft to reveal a world that is today a memory book of the early solar system, with a surface dominated by ancient highlands and basalt-filled plains known as lunar maria.

Orbit and physical characteristics

  • The Moon is about 1,737 kilometers in radius and has a mass of roughly 7.35 × 10^22 kilograms, making it the fifth largest natural satellite in the solar system and a substantial companion to Earth. It lacks a substantial atmosphere and possesses a weak magnetic field in some regions, a consequence of its small size and cool interior.
  • Its surface gravity is about 1.62 meters per second squared, roughly one-sixth that of Earth, which makes lunar exploration and sample collection fundamentally different from Earth-based operations.
  • The Moon completes one sidereal orbit around Earth roughly every 27.3 days, while the synodic cycle (phases from new Moon to new Moon) takes about 29.5 days. The orbital dynamics are governed by classical orbital mechanics, described in part by Kepler’s laws.
  • The Moon’s near side and far side reveal different geological histories: the near side contains extensive maria (basaltic plains), whereas the far side is more heavily cratered and has a thicker crust with relatively fewer maria. The linguistic and scientific terms for these regions are commonly discussed in Lunar maria and far side of the Moon articles.
  • The Moon’s surface is blanketed by regolith, a loose, disrupted layer of rock fragments produced by countless impacts. This regolith is an object of study for regolith science and helps explain how future surface operations might proceed.

For researchers, the Moon serves as a laboratory for selenology—the study of the Moon’s geology and history—and as a vantage point for broader solar system science. Its long exposure to space has preserved impact records that predate most surface processes on Earth, while its low gravity and stable lighting conditions on parts of the surface have made it attractive for long-duration experiments and observatories.

Geology and surface features

  • The lunar crust is largely made of anorthosite in the highlands and basalt in the maria. These rock types are central to our understanding of the Moon’s formation and thermal evolution, and they are studied in detail using samples returned from missions such as the Apollo program and robotic missions like Lunar Reconnaissance Orbiter.
  • The surface features include an immense number of impact craters, large lava-filled basins, rilles (valley-like features formed by ancient lava or tectonic processes), and mountain ranges created by the early bombardment and subsequent volcanic activity. The distribution and morphology of these features reflect the Moon’s early thermal state and the decline of geological activity over billions of years.
  • Water in solid form has been detected in permanently shadowed regions near the poles, where conditions remain cold enough to preserve ice. This has implications for future Lunar resource utilization and planetary science, and it has been studied by missions such as Chandrayaan-1 and Lunar Reconnaissance Orbiter.
  • The Moon’s interior structure is inferred from seismic data, gravity measurements, and sample analyses. There is a small, partially molten or partially differentiated core, with a crust that varies in thickness between the near side and far side. The interior remains a topic of ongoing research, with implications for the Moon’s thermal and tectonic history.

The Moon’s geology records a sequence of processes that include planet-scale formation, magma ocean crystallization, giant impacts, and billions of years of impact gardening. The study of lunar rocks—from anorthosites to basaltic mare basalts and breccias—has been essential in forming our broader understanding of planetary differentiation and the evolution of rocky bodies in the solar system.

Exploration and science

  • Early space exploration began with robotic missions from both the East and the West, including the Soviet Luna program and early United States probes. These missions provided the first data about the Moon’s surface composition, gravity field, and topography.
  • The Apollo program stands as the most prominent human exploration initiative, with missions that landed astronauts on the lunar surface, conducted surface science, and returned samples that transformed planetary geology. The first manned landing, completed by Neil Armstrong and Buzz Aldrin, demonstrated not only technical achievement but also the potential for sustained human activity beyond Earth.
  • Robotic and orbital missions have continued to expand our knowledge. The Lunar Reconnaissance Orbiter maps the surface in high resolution and supports landing-site selection and resource assessment. This program, along with others, informs ongoing discussions about how best to deploy assets in near-Earth space.
  • The Moon has become a focal point for contemporary space policy and private-sector activity. The Artemis program aims to return humans to the lunar surface and establish a sustainable presence, using partnerships with industry to develop the capabilities needed for deeper space exploration. Private companies have begun delivering science payloads and logistics services, illustrating a shift toward a more market-driven approach to space operations, while still requiring clear governance and international norms.

Key concepts and terms linked to lunar exploration include selenology, Kepler's laws of orbital mechanics, Regolith, Lunar maria, and Water on the Moon. The Moon also features in broader discussions about space governance, including the Outer Space Treaty and related policy developments such as the Artemis Accords.

Policy, economics, and controversies

  • The Moon sits at the intersection of science, national interest, and fiscal stewardship. Debates over how to allocate scarce public resources between crewed missions and robotic science often center on cost, risk, and expected scientific return. Advocates argue that human missions can accelerate learning, validate technology, and strengthen national capabilities, while critics emphasize the high price tag and the need to focus on incremental, cost-effective robotic exploration.
  • Resource policy on the Moon is a live, contested issue. The Outer Space Treaty sets constraints on national appropriation, while newer frameworks and accords discuss how mineral and resource extraction might proceed in practice. Proposals on Lunar resource utilization hinge on balancing scientific goals, commercial opportunity, and international norms—an ongoing negotiation among spacefaring nations and private actors.
  • Critics from various perspectives often argue that space investments should be tethered to tangible domestic benefits, such as advanced technologies and STEM education, and that public funds should not be for prestige or political signaling alone. Proponents contend that the Moon serves as a proving ground for systems and capabilities that enable future exploration, defense, and international collaboration.
  • From a pragmatic, market-friendly viewpoint, partnerships with private firms can lower costs, accelerate schedule, and foster domestic industry growth, provided there are clear protections for safety, liability, national security, and the long-term interests of science and humanity. This approach requires robust governance to avoid mission creep and ensure accountability, while preserving access to space as a shared frontier.

Controversies surrounding race, identity, and social policy are common in public discourse about science funding and institutions. In this context, proponents of a fiscally focused, results-oriented approach stress that the core objective should be reliable, repeatable science and sustainable technology development, while also recognizing the value of broad participation and education. Critics may frame these debates in terms of representation or social goals; a disciplined, rational policy framework seeks to align funding with concrete outcomes—without surrendering the foundational principles that enable ambitious exploration and national capability.

See also