611 articles
Mercury's magnetic field
Mercury's magnetic field is a global dynamo field generated in Mercury's liquid iron core, about 1% as strong as Earth's, making Mercury the only other inner planet with one.
Meteor
A meteor, called a falling star or shooting star, is the streak of light produced when a meteoroid enters a planetary atmosphere at high speed and usually vaporizes.
Meteor shower
A meteor shower, also called a meteor swarm or star shower, is a recurring increase in meteors seen when Earth passes through dust streams shed mainly by comets.
Meteorite
A meteorite, also called an aerolite, is a natural solid object from space that survives its fiery passage through an atmosphere. Most come from asteroids, with a few from the Moon and Mars.
Meteoroid
A meteoroid is a small natural solid object moving through interplanetary space, typically a fragment of a comet or asteroid, defined by the IAU as 30 micrometers to 1 meter.
Meteoroid stream
A meteoroid stream is a population of dust to pebble-sized particles sharing similar orbits because they were released from the same parent body, usually a comet.
Methane on Mars
Methane on Mars refers to trace methane gas reported in the Martian atmosphere since 2004, from Curiosity and Mars Express, whose origins, geological or biological, remain debated.
Methone (moon)
Methone (Saturn XXXII) is a small moon of Saturn about 3 kilometers across that orbits between Mimas and Enceladus and was discovered in Cassini images in 2004.
Minor planet
A minor planet, also called a planetoid, is a body orbiting the Sun that is neither a planet nor a comet, including asteroids, centaurs, and trans-Neptunian objects.
Minor Planet Electronic Circulars
Minor Planet Electronic Circulars (MPECs) are electronic bulletins issued by the Minor Planet Center, generally daily since 1993, announcing discoveries, orbits, and identifications of minor planets and comets.
Minor-planet designation
Minor-planet designation, also called asteroid designation, is the formal identifier for an asteroid, consisting of a provisional designation, a permanent number, and optionally a name.
Miranda (moon)
Miranda (Uranus V) is the smallest and innermost of Uranus's five major moons, discovered in 1948 and found by Voyager 2 in 1986 to have unique patchwork terrain called coronae.
Miyake events
Miyake events are sharp, globally synchronous spikes in atmospheric radiocarbon recorded in tree rings, first identified by physicist Fusa Miyake in 2012, most plausibly caused by extreme solar particle bursts far larger than any observed.
Mneme
Mneme (Jupiter XL, S/2003 J 21) is a small retrograde irregular moon of Jupiter in the Ananke group, discovered February 9, 2003 by Sheppard and Gladman at Mauna Kea; about 1 km in radius, orbiting ~21 million km away in ~620 days, named for the Muse of memory.
Moment of inertia factor
The moment of inertia factor, or normalized polar moment of inertia, is a dimensionless measure of how mass is distributed inside a planet, equal to 0.4 for a uniform sphere.
Moon
The Moon is Earth's only natural satellite, a rocky body about one-fourth Earth's size that orbits 384,400 km away. It likely formed from debris of a giant collision with Earth.
Moonfall (film)
Moonfall is a 2022 science-fiction disaster film directed by Roland Emmerich, starring Halle Berry, Patrick Wilson, and John Bradley, released in the United States in February 2022.
Moonlight
Moonlight is sunlight reflected from the Moon's surface, which produces no light of its own; its phases cycle each month, and it calibrates satellites and guides nocturnal ecology.
Moonquake
A moonquake is a seismic event on the Moon, driven by Earth's tidal pull, global contraction as the Moon cools, and impacts, recorded by Apollo seismometers between 1969 and 1977.
Moons of Jupiter
The moons of Jupiter, also called Jupiter's satellites, are natural satellites ranging from the four planet-sized Galilean moons to small captured bodies, with 115 recognized as of 2026.
Moons of Mars
The moons of Mars, Phobos and Deimos, are two small, dark, tidally locked satellites discovered by Asaph Hall in 1877, whose origin, captured asteroids or impact debris, remains unresolved.
Moons of Neptune
Neptune's moons are the 16 known natural satellites of Neptune, led by captured Kuiper Belt object Triton, with Nereid, Hippocamp, and six moons revealed by Voyager 2's 1989 flyby.
Moons of Pluto
The moons of Pluto are five: large Charon, discovered in 1978, and the small satellites Styx, Nix, Kerberos, and Hydra, discovered between 2005 and 2012, orbiting the Pluto–Charon pair.
Moons of Saturn
Saturn's moons are the natural satellites of Saturn, the most of any planet at 285 confirmed, ranging from Titan, larger than Mercury, to tiny irregular fragments.
Moons of Uranus
The moons of Uranus are its natural satellites, 29 recognized as of 2026, with five major moons named for characters from Shakespeare, visited only by Voyager 2 in 1986.
Moonshot (2022 film)
Moonshot is a 2022 American science fiction romantic comedy directed by Christopher Winterbauer, starring Cole Sprouse and Lana Condor, released on HBO Max on March 31, 2022.
Morning Star
The Morning Star is the planet Venus seen in the eastern sky before sunrise; the same planet appears as the Evening Star after sunset, alternating every 19 months.
Murchison meteorite
The Murchison meteorite is a carbonaceous chondrite that fell near Murchison, Victoria, Australia, in September 1969, becoming one of the most studied meteorites for its organic compounds.
Mutual events of Pluto and Charon
Mutual events of Pluto and Charon were eclipses and occultations from late 1984 to late 1990. The resulting light curves mapped Pluto's surface and helped discover its atmosphere.
Naming of moons
Naming of moons, or naming of natural satellites, is the process by which newly found moons get provisional designations and permanent names approved by the IAU, arbiter since 1919.