The Moon

The Moon is Earth's only natural satellite and the fifth largest moon in the solar system, with a diameter of 3,474.8 km, about 27 percent of Earth's, orbiting at an average distance of 384,400 km.^[16] It is the only world beyond Earth that people have visited, and after decades of neglect it has again become the busiest destination in spaceflight.

The Moon is unusually large relative to its parent planet, and the gravitational interplay between the two bodies raises ocean tides, stabilizes Earth's axial tilt, and slowly lengthens Earth's day. Tidally locked, the Moon always presents the same hemisphere to observers on the ground.

In April 2026 the Artemis II crew flew the first piloted mission beyond low Earth orbit since 1972.^[1] In March 2026 NASA paused its Gateway lunar-orbit station and shifted the Artemis program toward a proposed Moon Base near the south pole.^[9][10] NASA has not published a complete, funded construction schedule for the base. Commercial robotic landers carrying NASA instruments now attempt touchdowns most years, and China is preparing Chang'e 7, a four-spacecraft expedition to the lunar south pole, for launch in the second half of 2026.^[2] Much of this activity converges on a single resource: water ice locked inside permanently shadowed polar craters.

Formation#

The leading explanation for the Moon's origin is the giant-impact hypothesis. Roughly 4.5 billion years ago a Mars-sized body, often called Theia, struck the young Earth, and debris from the collision gathered into a disk that coalesced into the Moon. The scenario accounts for the Moon's small iron core, its depletion in water and other volatiles, and the high angular momentum of the Earth-Moon system. Oxygen isotope ratios in Apollo program samples are nearly identical to Earth's, which has pushed researchers toward variants involving a thoroughly mixed debris disk. The infant Moon was covered by a magma ocean; low-density minerals floated to its top and solidified into the pale highland crust visible today.

Dating the impact has proved harder than describing it. Most Apollo whole-rock samples cluster near 4.35 billion years, while rare zircon grains run as old as 4.51 billion years. A 2024 paper in Nature argued that the younger cluster records a later event rather than the original crystallization of the magma ocean: as the Moon's orbit passed through the Laplace plane transition, tidal heating remelted much of the body and reset the ages of most rocks, leaving the earlier zircons and the Moon's frozen-in shape as survivors. On that reading the Moon formed within a few tens of millions of years of the solar system itself.^[15]

Physical characteristics#

The Moon's surface gravity is 1.62 m/s², about one sixth of Earth's. The Moon completes an orbit of Earth every 27.3 days, and a full lunar day, sunrise to sunrise, spans 29.5 Earth days, so daylight and darkness each last about two weeks.^[45] There is no meaningful atmosphere, only a wispy exosphere, so equatorial temperatures swing from roughly 121 °C at local noon to -133 °C at night, and micrometeoroids strike the surface unimpeded. The exosphere is thin enough that its atoms almost never collide with one another. NASA's LADEE orbiter measured its main constituents, helium, neon, and argon, along with sodium and potassium, and watched argon-40 freeze onto the surface through the 14-day night and vent back out as the Sun returned.^[25] Everything is blanketed by regolith, a layer of fine, abrasive impact debris several meters deep.

Two terrains dominate: ancient, heavily cratered highlands, and darker basaltic plains called maria that flooded large impact basins, mostly on the near side. NASA puts the mare lavas between about 4.2 and 1.2 billion years ago, and returned samples keep widening that window; Chang'e 5 collected basalts about 2 billion years old, and Chang'e 6 found far side eruptions at roughly 4.2 and 2.8 billion years.^[16][19] Laser ranging to retroreflectors left by Apollo 11, 14, and 15 shows the Moon receding from Earth by 3.8 cm per year, a figure now measured to within millimeters.^[24]

Interior and seismicity#

Beneath the crust the Moon is layered much as Earth is, on a smaller scale. NASA describes a solid, iron-rich inner core about 240 km in radius, wrapped in a liquid iron shell roughly 90 km thick and overlain by a deep silicate mantle.^[16] A 2023 study in Nature that combined lunar laser ranging with spacecraft tracking put the inner core nearer 258 km in radius at a density close to iron's, and argued that the lunar mantle overturned early in its history, sinking dense material toward the core and lifting lighter material up.^[17]

The only seismic network ever operated on another world came from Apollo. Stations at the Apollo 12, 14, 15, and 16 sites detected more than 12,000 seismic events between 1969 and 1977, distinguishing meteoroid impacts, shallow quakes, deep quakes driven by tidal stress, and thermal cracking as the surface heats and cools.^[18] NASA switched the network off in 1977. Nothing has replaced it, which is why several planned landers carry seismometers.

Water ice at the poles#

Because the Moon's spin axis tilts only about 1.5 degrees, the floors of some polar craters never receive direct sunlight. NASA's Lunar Reconnaissance Orbiter has measured temperatures there as low as about 25 kelvin, roughly -248 °C, in Hermite crater near the north pole, the coldest readings taken anywhere in the solar system.^[37] Cold traps that deep can hold water for billions of years. Hydrogen signals detected by Lunar Prospector in 1998, followed by a spectral detection of water and hydroxyl in 2009 by NASA's Moon Mineralogy Mapper aboard ISRO's Chandrayaan-1 orbiter, pointed to ice in these craters.^[33] Direct proof came on October 9, 2009, when the LCROSS mission steered a spent Centaur rocket stage into Cabeus crater near the south pole. NASA announced on November 13, 2009 that the plume contained water, and instruments on LCROSS and the Lunar Reconnaissance Orbiter found that as much as 20 percent of the ejected material was volatiles, including methane, ammonia, carbon dioxide, and carbon monoxide, alongside light metals.^[3][43] The mission team put the ice content of the excavated soil at roughly 5.6 percent by mass, and later work reconciling that figure with orbital neutron measurements bracketed it at 3 to 10 percent while concluding the deposits are patchy rather than evenly spread.^[23][44]

How much ice sits at the very surface is still contested. ShadowCam, an ultrasensitive NASA camera flying on South Korea's Danuri orbiter, imaged permanently shadowed regions at high resolution, and a March 2026 analysis in Science Advances reported no evidence of widespread surface ice above a detection limit of 20 to 30 percent by weight. Only a few small patches showed the brightness and scattering behavior consistent with more than 10 percent ice, far less than models predict and far less than Mercury and Ceres show. The authors note that buried or low-concentration ice would escape the technique entirely, and that settling the question needs instruments sensitive below 1 percent.^[22]

Ice matters because water is the heaviest consumable a lunar program would otherwise ship from Earth. Split into hydrogen and oxygen, it becomes breathable air and rocket propellant. That is why nearly every major mission now planned, from Artemis landings to Chang'e 7, targets the south polar region.

Luna, Apollo, and the long gap#

The Soviet Union opened lunar exploration: Luna 2 struck the lunar surface in September 1959, Luna 3 photographed the far side a month later, and Luna 9 achieved the first soft landing on February 3, 1966. The United States answered with the crewed Apollo program. Apollo 8 orbited the Moon in December 1968, and on July 20, 1969, Apollo 11 landed Neil Armstrong and Buzz Aldrin at Tranquility Base. Six landings through Apollo 17 in December 1972 put twelve astronauts on the surface and returned 382 kg of rock and soil in 2,196 individual samples, while Soviet robotic landers scooped up their own samples through Luna 24 in 1976.

Then interest collapsed. No spacecraft visited the Moon between 1976 and 1990, and nothing landed softly again until China's Chang'e 3 in December 2013. Orbiters led the return: Clementine in 1994, Lunar Prospector in 1998, and NASA's Lunar Reconnaissance Orbiter, mapping the surface since 2009. China's Chang'e 5 brought back 1,731 grams of basalt in December 2020, India's Chandrayaan-3 landed in the south polar region in August 2023, and JAXA's SLIM demonstrated precision landing in January 2024. Not every return succeeded: Roscosmos sent Luna 25 toward the south pole in August 2023, its first lunar mission since 1976, and lost it when an engine burn put the spacecraft into an unplanned orbit and it hit the surface on August 19.^[39]

The current rush to the Moon#

Under NASA's Commercial Lunar Payload Services (CLPS) program, private companies deliver agency instruments to the lunar surface for fixed prices. The record so far is mixed. Astrobotic's Peregrine leaked propellant shortly after launch in January 2024 and never attempted a landing.^[32] Intuitive Machines' IM-1 made the first commercial soft landing on February 22, 2024, at Malapert A near the south pole, though it tipped onto its side.^[32] Firefly Aerospace's Blue Ghost Mission 1 achieved the first fully successful commercial landing on March 2, 2025, touching down near Mons Latreille in Mare Crisium.^[4][34] It worked through 346 hours of daylight and roughly five more into the lunar night, returned about 119 gigabytes of data from ten NASA payloads, and photographed a total lunar eclipse from the surface on March 14.^[34] Four days after Blue Ghost arrived, Intuitive Machines' IM-2 lander Athena came down on March 6 about 250 meters off target, inside a shadowed crater near Mons Mouton, and toppled onto its side. With its solar panels facing the wrong way in the cold, it could not recharge; NASA collected some data before the mission was called the next day.^[30][41] ispace's Resilience, flying outside CLPS, crashed in Mare Frigoris on June 6, 2025, after its laser rangefinder failed to return valid altitude readings during descent.^[31]

The 2026 manifest has slipped repeatedly. Astrobotic's Griffin, carrying Venturi Astrolab's FLEX Lunar Innovation Platform rover to the Nobile region of the south pole, moved from November 2025 to a window opening in July 2026 and is now expected later in the year.^[36] Intuitive Machines' IM-3, bound for the Reiner Gamma magnetic swirl, is targeted for the second half of 2026, and Firefly's Blue Ghost Mission 2 for late in the year.^[5] Blue Origin's cargo lander Blue Moon MK1, named Endurance, completed thermal vacuum testing at NASA's Johnson Space Center in May 2026 and has been designated for the first Moon Base delivery to the south pole, but its launch waits on New Glenn returning to flight after a booster exploded during a static fire on May 28, 2026.^[6][14] One mission dropped off the list entirely: NASA and Draper ended the CP-12 task order in July 2026 after lander redesigns pushed a far side delivery to Schrödinger basin out to about 2030. NASA said it would fly the already-built seismic and heat-flow instruments on a later CLPS mission.^[11]

The program is nonetheless expanding. In September 2025 NASA revived VIPER, the ice-prospecting rover it had cancelled the year before, assigning it to a Blue Moon MK1 flight targeted for late 2027 under a task order worth up to 190 million dollars; the rover is designed to work for about 100 days at the south pole.^[12] In July 2026 the agency awarded nearly 600 million dollars to Astrobotic, Firefly Aerospace, and Intuitive Machines for four more cargo landings in late 2028, each carrying the same three payloads: a camera set that films engine plumes hitting the surface, a laser retroreflector for navigation, and a radiation spectrometer.^[13]

Crewed flight resumed with Artemis II, launched April 1, 2026 on the Space Launch System. Astronauts Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen looped their Orion capsule around the Moon on April 6, traveled farther from Earth than any previous crew, and splashed down on April 10 after ten days.^[1] NASA plans Artemis III in 2027 as an Earth-orbit rendezvous and docking test with lander hardware, followed by Artemis IV, targeted for 2028 as the first crewed landing at the lunar south pole.^[7]

China's Chang'e 7, built by the China National Space Administration, arrived at the Wenchang spaceport in April 2026 for launch on a Long March 5. It combines an orbiter, a lander, a rover, and a legged hopper designed to fly into permanently shadowed craters, drill, and analyze ice with a mass spectrometer, and carries 18 science payloads in all, several of them contributed by Egypt, Italy, Russia, Switzerland, and Thailand. Launch is expected in the second half of 2026, with the landing targeted near the illuminated rim of Shackleton crater and communications routed through the Queqiao-2 relay satellite already in lunar orbit.^[2][8] China has also stated its intent to land astronauts before 2030.

Far side science#

The Moon's far side is not dark (both hemispheres receive equal sunlight) but it is different. Gravity mapping by NASA's GRAIL mission put its crust at about 60 km thick against 40 km on the near side, which made it far harder for mantle magma to reach the surface, and it carries almost no maria.^[40] It hosts the South Pole-Aitken basin, an impact scar roughly 2,500 km across and up to 8 km deep, the largest confirmed in the solar system. Chang'e 6 samples dated the impact to about 4.25 billion years ago, giving lunar crater chronology its oldest calibration point.^[20]

China's Chang'e 4 made the first far side landing on January 3, 2019, in Von Kármán crater, and Chang'e 6 returned 1,935.3 grams of South Pole-Aitken material in June 2024, the first samples from the far hemisphere; both depended on Queqiao relay satellites because the Moon blocks direct radio contact.^[42] Analysis of the Chang'e 6 basalts has produced the first real picture of the far side interior. Eruptions there continued to at least 2.8 billion years ago, extending the known record by more than a billion years.^[19] The source mantle is drier than the near side's, holding roughly 1 to 1.5 micrograms of water per gram, and cooler by about 100 °C.^[21] Gravity modeling published in June 2026 by researchers at the Southwest Research Institute concluded that the basin formed from a low-angle impact by a differentiated body and scattered mantle-derived rock across the region, with traces of it plausibly within reach of crews landing near the south pole.^[26]

The far side is also shielded from Earth's radio chatter, which makes it prized ground for low-frequency radio astronomy. Blue Ghost Mission 2 is slated to deliver LuSEE-Night, a pathfinder low-frequency radio telescope built by NASA, the Department of Energy, and the University of California, Berkeley, while Firefly's Elytra orbiter places Lunar Pathfinder, a communications relay built by Surrey Satellite Technology in partnership with the European Space Agency, into lunar orbit.^[5][38]

Future bases and resources#

The United States and China both aim at permanent infrastructure near the lunar south pole. NASA replaced its Artemis Base Camp concept in March 2026 with a Moon Base program organized in three phases: robotic landings and technology tests through 2029, then power, communications, navigation, and cargo infrastructure with two crewed missions a year from 2029 to 2032, then habitats and long-range surface mobility after that.^[9][10] Nuclear power is central to the plan, since a base at the pole must survive periods without sunlight; NASA and the Department of Energy signed an agreement in January 2026 to field a lunar fission surface power system by 2030.^[35] NASA has contracted SpaceX's Starship lander and Blue Origin's Blue Moon MK2 for crewed landings, but after the 2026 replan it has not committed either vehicle to a specific mission, saying the first landings will fly on whichever lander is ready.^[7]

The China-led International Lunar Research Station follows a parallel track, with a basic facility at the south pole targeted for 2035 and more than a dozen partner countries signed on. Chang'e 8, planned for 2028 or 2029 at a plateau near Mons Mouton, is its main technology precursor: it will test in-situ resource use, including 3D printing bricks from lunar soil melted by concentrated sunlight, and carries payloads selected from eleven countries.^[29] India and Japan are preparing their own polar prospecting mission, LUPEX, which India counts as Chandrayaan-5. The two agencies signed the implementing arrangement in August 2025; ISRO builds the lander, JAXA the 350 kg rover and its 1.5-meter drill, and launch on an H3 rocket is no earlier than 2028.^[28]

Long-term plans depend on living off the land: cracking ice into propellant, extracting oxygen from regolith, and building shelter from lunar soil. The obstacles are concrete ones: 14-day nights, abrasive dust that degrades seals and equipment, radiation, and unproven mining economics. Helium-3 is the resource most often cited and the least settled. No power reactor exists that could burn it, so the near-term case rests on smaller markets such as cryogenics for quantum computing and medical imaging. NASA gave the idea its first formal backing in May 2026, awarding the Seattle company Interlune a 6.9 million dollar Small Business Innovation Research contract to build a payload that heats regolith and measures the helium-3 and hydrogen it releases, for flight on a commercial lander in 2028.^[27] Compared with Mars, though, the Moon is three days away, and that proximity keeps it the proving ground for everything meant to go deeper.

References#

1. NASA Welcomes Record-Setting Artemis II Moonfarers Back to Earth - NASA.
2. China's Chang'e-7 arrives at spaceport for lunar south pole exploration mission - SpaceNews, April 10, 2026.
3. NASA Missions Uncover the Moon's Buried Treasures - NASA.
4. Touchdown! Carrying NASA Science, Firefly's Blue Ghost Lands on Moon - NASA, March 2, 2025.
5. Moon rush: These private spacecraft will attempt lunar landings in 2026 - Space.com.
6. Blue Origin Moon Lander Completes Testing at NASA Vacuum Chamber - NASA.
7. NASA Marches Toward Artemis III Mission in 2027, Names Crew Members - NASA.
8. Hopping robot will hunt for moon water on China's Chang'e 7 lunar mission in 2026 - Space.com.
9. Moon Base Phases - NASA.
10. NASA outlines ambitious $20 billion plan for moon base - Spaceflight Now, March 25, 2026.
11. NASA terminates Draper lunar lander mission - SpaceNews, July 2026.
12. NASA Selects Blue Origin to Deliver VIPER Rover to Moon's South Pole - NASA, September 2025.
13. NASA Awards More Moon Base Science, Previews New Opportunities - NASA, July 2026.
14. After New Glenn anomaly, Blue Origin keeps focus on upcoming Blue Moon and Mars missions - NASASpaceflight, June 2026.
15. Tidally driven remelting around 4.35 billion years ago indicates the Moon is old - Nature, December 2024.
16. Moon Facts - NASA Science.
17. The lunar solid inner core and the mantle overturn - Nature, May 2023.
18. Passive Seismic Experiment (Apollo) - NASA Space Science Data Coordinated Archive.
19. Lunar farside volcanism 2.8 billion years ago from Chang'e-6 basalts - Nature.
20. South Pole-Aitken massive impact 4.25 billion years ago revealed by Chang'e-6 samples - National Science Review, 2025.
21. A relatively cool lunar farside mantle inferred from Chang'e-6 basalts and remote sensing - Nature Geoscience, 2025.
22. Searching for surficial water ice in lunar permanently shaded regions (PSRs) with ShadowCam - Science Advances, March 18, 2026.
23. Reconciling LCROSS and Orbital Neutron Water Abundance Estimates in Cabeus Crater - NASA Technical Reports Server.
24. The Apollo Experiment That Keeps on Giving - NASA Jet Propulsion Laboratory.
25. What is LADEE, the Lunar Atmosphere and Dust Environment Explorer? - NASA.
26. SwRI team uncovers clues about what future astronauts may find on the Moon - Southwest Research Institute, June 15, 2026.
27. Interlune wins NASA contract for helium-3 extraction payload - SpaceNews, May 2026.
28. Lunar Polar Exploration (LUPEX) - JAXA.
29. China selects international payloads for Chang'e-8 lunar south pole mission - SpaceNews.
30. NASA Receives Some Data Before Intuitive Machines Ends Lunar Mission - NASA, March 2025.
31. ispace's Resilience lander crash lands on the Moon - Spaceflight Now, June 6, 2025.
32. Commercial Lunar Payload Services (CLPS) Deliveries - NASA Science.
33. NASA Instruments Reveal Water Molecules on Lunar Surface - NASA Jet Propulsion Laboratory.
34. Firefly Aerospace wraps up successful Blue Ghost 1 mission - SpaceNews, March 2025.
35. NASA, Department of Energy to Develop Lunar Surface Reactor by 2030 - NASA, January 13, 2026.
36. Astrobotic delays Griffin-1 Moon mission to NET July 2026 - Spaceflight Now.
37. Moon Craters Could Be Coldest Place in Solar System - Space.com.
38. Lunar Pathfinder - European Space Agency.
39. The Russian space agency says its Luna 25 spacecraft has crashed into the moon - NPR, August 20, 2023.
40. Moon Composition - NASA Science.
41. Intuitive Machines' IM-2 Moon mission ends with lander on its side - Spaceflight Now, March 7, 2025.
42. China's Chang'e-6 collects 1935.3 grams of samples from the moon's far side - China National Space Administration.
43. LCROSS - NASA Science.
44. Detection of Water in the LCROSS Ejecta Plume - Science, October 2010.
45. Moon Phases - NASA Science.