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Meteorite glossary

600 words used about meteorites, fireballs, craters and the Solar System, each explained in plain English. Every term is labelled with its level, from beginner to expert.

2 Δ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

2 Δ

2008 TC3 Enthusiast: 2008 TC3 was the first asteroid discovered before hitting Earth; its fragments were recovered as the Almahata Sitta meteorites.
Δ17O (cap delta O-17) Expert: Δ17O measures how far a sample's oxygen isotope composition lies from Earth's mass-fractionation line, and it identifies meteorite parent bodies.

A

Ablation Explorer: Ablation is the melting and vaporising of a meteoroid's surface as it speeds through the atmosphere.
Acapulcoite Expert: Acapulcoites are fine-grained primitive achondrites that experienced only small degrees of partial melting.
Achondrite Explorer: An achondrite is a stony meteorite that has been melted, so it has no chondrules.
Active asteroid Expert: An active asteroid is an asteroid that loses dust or gas, for any reason, making it look briefly like a comet.
Aerogel Enthusiast: Aerogel is an ultra-light, porous glass foam used by the Stardust mission to catch fast-moving comet dust.
Age of the Solar System Explorer: About 4.567 billion years, measured from the oldest solid grains found inside meteorites.
Airburst Explorer: An airburst is when an incoming space rock explodes in the atmosphere instead of hitting the ground in one piece.
Akaganeite Expert: Akaganeite is a chlorine-bearing iron oxyhydroxide that causes iron meteorites to crack and weep rust.
Akimotoite Expert: Akimotoite is a very dense high-pressure form of pyroxene chemistry discovered in a shocked meteorite.
Albedo Explorer: Albedo is the fraction of light that a surface reflects, from 0 for perfectly black to 1 for perfectly white.
Albite Expert: Albite is the sodium-rich end of the plagioclase feldspar series, found as small grains in equilibrated chondrites.
ALH 84001 Enthusiast: ALH 84001 is an ancient Martian meteorite found in Antarctica, famous for the 1996 claim of possible microfossils.
All-sky camera Explorer: A camera with a fisheye lens that watches the whole sky at once, automatically recording meteors and fireballs.
Almahata Sitta Enthusiast: Almahata Sitta is the meteorite from asteroid 2008 TC3, which fell in Sudan in 2008 and contains many meteorite types.
Aluminium foil handling Enthusiast: Fresh meteorites are often picked up with clean aluminium foil to avoid contaminating them with skin oils and organic matter.
Aluminium-26 Expert: A short-lived radioactive isotope of aluminium, now extinct in early solar-system materials, that dated and heated the first planetesimals.
Amino acids Enthusiast: Amino acids are small carbon-based molecules, the building blocks of proteins, and some meteorites contain ones made without life.
Amoeboid olivine aggregate Expert: An amoeboid olivine aggregate is an irregular, fine-grained clump of olivine with small calcium-aluminium-rich nodules that formed by condensation in the early solar nebula.
Amor asteroid Enthusiast: An Amor asteroid is a near-Earth asteroid that approaches Earth's orbit from outside without crossing it.
Angrite Expert: A rare, extremely old basaltic achondrite rich in calcium and aluminium and strongly depleted in volatile elements.
Anomalous meteorite Expert: An anomalous meteorite mostly fits a known group but differs from it in some important way.
Anorthite Expert: Anorthite is the calcium-rich end of the plagioclase feldspar series, common in CAIs, eucrites and the lunar highlands.
Anorthosite Enthusiast: Anorthosite is a pale igneous rock made almost entirely of plagioclase feldspar; it forms the Moon's bright highlands.
ANSMET Enthusiast: The Antarctic Search for Meteorites, a long-running United States programme that sends field teams to collect meteorites from the Antarctic ice.
Antarctic meteorite Explorer: A meteorite collected in Antarctica, where moving ice gathers fallen rocks into places that make them easy to find.
Antarctic Treaty Enthusiast: The Antarctic Treaty governs activities in Antarctica, where meteorites are collected only by scientific programmes.
Apatite Enthusiast: Apatite is a calcium phosphate that can contain water, fluorine and chlorine, making it a tracer of volatiles in meteorites.
Aphelion Explorer: Aphelion is the point in an orbit where an object is farthest from the Sun.
Apollo asteroid Enthusiast: An Apollo asteroid is a near-Earth asteroid whose orbit crosses Earth's and is larger than Earth's orbit.
Apollo samples Explorer: Apollo samples are the 382 kilograms of Moon rock and soil collected by astronauts between 1969 and 1972.
Apparent magnitude Explorer: A number that describes how bright an object looks from Earth; the smaller the number, the brighter it appears.
Aqueous alteration Enthusiast: Aqueous alteration is the chemical change of a meteorite's minerals by liquid water inside its parent asteroid.
Argon–argon dating Expert: A refinement of potassium–argon dating that measures argon isotopes after neutron irradiation, widely used to date heating and impact events.
Arrokoth Enthusiast: Arrokoth is a small, red, two-lobed Kuiper Belt object visited by New Horizons in 2019, the most distant body ever explored up close.
Asteroid Beginner: A rocky or metal-rich object, smaller than a planet, that goes around the Sun.
Asteroid belt Beginner: The wide ring of space between Mars and Jupiter where most known asteroids travel around the Sun.
Asteroid designation Enthusiast: An asteroid designation is the code or number given to an asteroid, such as 2008 TC3 or 101955 Bennu.
Asteroid family Enthusiast: A group of asteroids with similar orbits that are fragments of one larger body broken apart by a collision.
Asteroid spectral class Enthusiast: A label, such as C, S or V, given to an asteroid based on the pattern of sunlight it reflects, which hints at what it is made of.
Astrobleme Enthusiast: An old, heavily eroded scar left by an ancient impact, often no longer looking like a crater at all.
Astronomical unit Explorer: An astronomical unit is the average distance from Earth to the Sun, about 149.6 million kilometres.
Ataxite Enthusiast: A nickel-rich iron meteorite that shows no visible structure when etched.
Aten asteroid Enthusiast: An Aten asteroid is a near-Earth asteroid with an orbit smaller than Earth's that crosses Earth's path.
Atira asteroid Expert: An Atira asteroid orbits entirely inside Earth's orbit, never coming farther from the Sun than Earth does.
Atmospheric entry Explorer: Atmospheric entry is the fiery plunge of a meteoroid or spacecraft into a planet's air, where it slows and heats up.
Aubrite Enthusiast: A pale achondrite made almost entirely of iron-free enstatite pyroxene, formed under very oxygen-poor conditions.
Augite Enthusiast: Augite is a calcium-rich clinopyroxene common in basalts on Earth, the Moon and Mars.
Australasian tektites Expert: Australasian tektites are natural glass objects scattered across a tenth of Earth's surface by an impact about 788,000 years ago.

B

Barred olivine chondrule Enthusiast: A barred olivine chondrule is a chondrule made of parallel plates of olivine inside an olivine rim, like a grille inside a ring.
Basalt Explorer: A dark, fine-grained volcanic rock made mainly of pyroxene and plagioclase feldspar, found on Earth and on other worlds.
Basaltic eucrite Enthusiast: A basaltic eucrite is a lava rock from Vesta's crust, made of pigeonite and calcium-rich plagioclase.
Basaltic shergottite Enthusiast: A basaltic shergottite is a Martian lava rock made mainly of pyroxene and shocked plagioclase.
Bennu Enthusiast: A dark, rubble-pile near-Earth asteroid about half a kilometre across, sampled by NASA's OSIRIS-REx mission.
Beryllium-10 Expert: Beryllium-10 is a radioactive isotope made by cosmic rays, used to measure exposure and terrestrial ages of meteorites.
Binary asteroid Explorer: A binary asteroid is a pair of asteroids orbiting each other, often a large body with a small moon.
Bolide Explorer: A bolide is a very bright fireball, often one that explodes or breaks apart in the sky.
Brachinite Expert: Brachinites are olivine-rich primitive achondrites from an oxidised parent body.
Breccia Explorer: A breccia is a rock made of broken, angular fragments of older rocks stuck together into a new rock.
Breccia lens Expert: A breccia lens is a lens-shaped layer of broken rock that fills the bottom of a simple impact crater.
Bridgmanite Expert: Bridgmanite is the most abundant mineral inside Earth, first found in nature in the shocked Tenham meteorite.
Bulk composition Enthusiast: Bulk composition is the overall chemistry of a whole meteorite sample, rather than of its individual minerals.

C

C-type asteroid Explorer: A C-type asteroid is a dark, carbon-rich asteroid, linked to carbonaceous chondrite meteorites.
Calcite Enthusiast: Calcite is calcium carbonate, found in meteorites both from water on asteroids and from weathering on Earth.
Calcium-aluminium-rich inclusion (CAI) Enthusiast: CAIs are pale, irregular inclusions rich in calcium and aluminium that are the oldest dated solids formed in the Solar System.
Carbide Enthusiast: A carbide is a mineral made of a metal or silicon bonded to carbon, such as cohenite in iron meteorites.
Carbon-14 terrestrial dating Enthusiast: Measuring cosmic-ray-made carbon-14 left in a meteorite to estimate how many thousands of years ago it fell.
Carbonaceous chondrite Explorer: A carbonaceous chondrite is a rare, usually dark chondrite that contains water-bearing minerals and carbon-rich compounds.
Carbonates Enthusiast: Minerals containing carbon and oxygen, such as calcite, that form in meteorites when water flows through rock.
CB chondrite Expert: CB chondrites are extremely metal-rich carbonaceous chondrites whose chondrules and metal probably condensed from an impact-generated vapour plume.
CCAM line Expert: The CCAM line is a line on oxygen isotope plots defined by anhydrous minerals of carbonaceous chondrites, with a slope near 1.
Centaur Expert: A Centaur is a small icy body orbiting between Jupiter and Neptune, partway between a Kuiper Belt object and a comet.
Central peak Explorer: A mountain or cluster of hills in the middle of a complex crater, made of rock pushed up from deep below.
Ceres Explorer: The largest object in the asteroid belt, about 940 kilometres across, classed as a dwarf planet since 2006.
Certificate of authenticity Explorer: A certificate of authenticity is a document from a seller stating that a meteorite is genuine; it is only as reliable as its issuer.
CH chondrite Expert: CH chondrites are metal-rich carbonaceous chondrites dominated by tiny chondrules and fragments, with very little matrix.
Chalcophile element Expert: A chalcophile element prefers to combine with sulfur, such as copper, zinc, selenium and lead.
Chang'e 5 Enthusiast: Chang'e 5 was a Chinese mission that brought back 1.73 kilograms of young lunar rock and soil in 2020.
Chang'e 6 Enthusiast: Chang'e 6 was a Chinese mission that returned the first samples from the far side of the Moon in 2024.
Chassignite Expert: A very rare Martian meteorite made mostly of olivine, a cumulate rock known as a dunite.
Chemical group Enthusiast: A chemical group is a set of meteorites with closely matching chemistry, minerals and isotopes, believed to come from the same parent body.
Chlorine-36 Expert: Chlorine-36 is a cosmic-ray-produced isotope used to measure how long a meteorite has been on Earth.
Chondrite Beginner: A chondrite is a stony meteorite full of tiny round grains called chondrules, and almost unchanged since the Solar System formed.
Chondrite classes Enthusiast: Chondrites are divided into classes, mainly ordinary, carbonaceous and enstatite, and then into groups within each class.
Chondrule Beginner: A chondrule is a tiny round grain, often smaller than a grain of rice, that formed as a melted droplet in space before the planets existed.
Chromite Enthusiast: A hard, black iron-chromium oxide mineral found in most stony meteorites and remarkably resistant to weathering.
CI chondrite Enthusiast: CI chondrites are rare, very crumbly carbonaceous chondrites whose chemistry closely matches that of the Sun.
Citizen science Beginner: Citizen science is research in which members of the public help scientists by collecting or analysing data.
CK chondrite Expert: CK chondrites are oxidised, thermally metamorphosed carbonaceous chondrites rich in magnetite.
Clan Expert: A clan is a set of meteorite groups that share important features and probably formed in neighbouring regions.
Classification Explorer: Classification is the process of identifying exactly what kind of meteorite a specimen is and giving it an official type and group.
Classification fee Expert: Some labs charge for classifying a meteorite, though many still keep a type specimen sample instead of payment.
Clast Explorer: A clast is a single fragment of rock or mineral that is embedded in a larger rock, especially a breccia.
Clinopyroxene Enthusiast: Clinopyroxene is the group of pyroxene minerals with a monoclinic crystal structure, including augite and pigeonite.
Closure temperature Expert: The closure temperature is the temperature below which a mineral stops losing the daughter isotopes of a radioactive clock.
Cloudy zone Expert: The cloudy zone is a fine intergrowth of nickel-rich particles at the edges of taenite that records cooling rate and ancient magnetism.
CM chondrite Enthusiast: CM chondrites are water-altered carbonaceous chondrites that contain small chondrules and rich organic chemistry.
CO chondrite Enthusiast: CO chondrites are carbonaceous chondrites packed with very small chondrules in a modest amount of matrix.
Coesite Expert: Coesite is a dense, high-pressure form of silica (SiO2) that, in surface rocks, is usually a fingerprint of a meteorite impact.
Cohenite Expert: An iron-nickel carbide mineral, (Fe,Ni)₃C, found mainly in carbon-rich iron meteorites.
Coma Beginner: A coma is the fuzzy cloud of gas and dust that surrounds a comet's nucleus as it nears the Sun.
Comet Beginner: An icy, dusty object from the outer Solar System that grows a glowing head and tail when it comes near the Sun.
Comet break-up Enthusiast: A comet break-up is when a comet splits into fragments, often because of heating, spinning or tidal forces.
Comet Encke Enthusiast: Comet Encke, 2P/Encke, is a small comet with the shortest known orbit of any bright comet, about 3.3 years.
Comet Interceptor Expert: Comet Interceptor is a planned European mission designed to wait in space and then visit a pristine comet or interstellar object.
Comet nucleus Explorer: A comet nucleus is the solid icy body at the heart of a comet, usually a few kilometres across and very dark.
Comet tail Beginner: A comet's tails are long streams of dust and gas pushed away from the Sun by sunlight and the solar wind.
Complex crater Explorer: A larger impact crater whose floor has collapsed and rebounded, giving it a flat floor, terraced walls and a central peak or ring.
Concretion Explorer: A hard, often rounded lump that grows inside sediment when minerals slowly glue the grains together, and is often mistaken for a meteorite.
Condensation Enthusiast: Condensation is the formation of solid grains directly from a cooling gas, the first step in making planets.
Constellation Beginner: A constellation is a named pattern of stars and the region of sky around it; meteor showers are named after them.
Contact binary Enthusiast: A contact binary is a small body made of two lobes that have gently come together and touch.
Cooling rate Enthusiast: A cooling rate is how quickly a rock or metal lost heat, often measured in degrees per million years for meteorites.
Corundum Expert: Corundum is aluminium oxide, the first mineral predicted to condense from hot solar gas, and some meteoritic grains are presolar.
Cosmic-ray exposure age Enthusiast: An estimate of how long a meteoroid travelled through space as a small body, based on the effects of cosmic rays on its atoms.
Cosmogenic nuclide Enthusiast: A cosmogenic nuclide is an isotope created when cosmic rays strike atoms in a rock exposed in space or at the surface.
CR chondrite Expert: CR chondrites are metal-bearing carbonaceous chondrites with large chondrules rich in iron-nickel metal and exceptionally primitive organic matter.
Crater chain Expert: A crater chain is a line of craters, made by a broken-up comet or asteroid or by ejecta from a large impact.
Crater counting Enthusiast: A way of estimating how old a planetary surface is by counting how many craters it has: more craters means an older surface.
Crater ellipticity Expert: Most craters are round even when the impactor arrived at a slant; only very low-angle impacts make elongated craters.
Crater lake Beginner: A crater lake is a lake that fills an impact crater or volcanic crater.
Crater rim Beginner: The raised, circular edge that runs around the top of an impact crater.
Cristobalite Expert: Cristobalite is a high-temperature form of silica found in some eucrites, Martian and lunar rocks.
Cronstedtite Expert: Cronstedtite is an iron-rich serpentine mineral typical of mildly altered CM chondrites.
Crusted individual Explorer: A whole, unbroken meteorite that is still covered with the dark fusion crust it gained during its fall.
Cryptocrystalline chondrule Expert: A cryptocrystalline chondrule has crystals so small they cannot be seen with an ordinary microscope.
Crystal Beginner: A crystal is a solid in which atoms are arranged in a neat, repeating three-dimensional pattern.
Crystallisation Explorer: Crystallisation is the growth of crystals from a melt, a gas or a solution, or within a solid as it is heated.
Crystallisation age Enthusiast: A crystallisation age is the time since a rock solidified from melt, measured with radiometric dating.
Cultural heritage law Enthusiast: Cultural heritage laws in some countries treat meteorites as protected national property, limiting collection and export.
Cumulate Expert: A cumulate is an igneous rock formed when crystals settle and pile up in a body of magma.
Cumulate eucrite Expert: A cumulate eucrite is a coarse-grained Vesta rock formed when crystals settled out of magma.
Curation Enthusiast: The careful storing, cataloguing, protecting and sharing of meteorites and other samples so they stay useful for science.
CV chondrite Enthusiast: CV chondrites are carbonaceous chondrites with large chondrules and many white calcium-aluminium-rich inclusions.

D

Dark adaptation Beginner: The way your eyes slowly become more sensitive in the dark, letting you see faint stars and meteors.
Dark flight Explorer: Dark flight is the last part of a meteorite's fall, after it has slowed down and stopped glowing.
Dark inclusion Expert: A dark inclusion is a fragment of darker, finer-grained chondritic rock embedded in a CV or other carbonaceous chondrite.
DART Enthusiast: DART was a NASA spacecraft that crashed into the asteroid moon Dimorphos in 2022 to test deflecting an asteroid.
Darwin glass Expert: Darwin glass is a natural impact glass found in Tasmania, formed by the impact that made Darwin Crater.
Dashcam footage Beginner: Dashcam footage is video from car cameras, which often captures bright fireballs and helps scientists trace them.
Daubréelite Expert: Daubréelite is an iron-chromium sulfide that forms thin plates in troilite in iron meteorites and enstatite meteorites.
Dawn mission Enthusiast: Dawn was a NASA mission that orbited the asteroid Vesta and the dwarf planet Ceres, using ion engines.
Daytime meteor shower Enthusiast: A daytime meteor shower has its radiant near the Sun, so its meteors are detected mostly by radio rather than seen.
Decay constant Expert: A decay constant is the fixed probability per unit time that a radioactive nucleus will decay.
Deep Impact Enthusiast: Deep Impact was a NASA mission that fired an impactor into comet Tempel 1 in 2005 to see what lay beneath its surface.
Deimos Explorer: Deimos is the smaller, outer moon of Mars, about 12 kilometres across and smoothed by dust.
Delta notation Expert: Delta notation expresses a small isotope ratio difference from a standard in parts per thousand, written δ.
Dense collection area Expert: A dense collection area is a region where so many meteorites are found that they are named with the area's name plus a number rather than separate place names.
Density Explorer: Density is how much mass is packed into a given volume, and most meteorites are denser than typical Earth rocks.
Desert varnish Explorer: Desert varnish is a thin, dark, shiny coating that builds up on rocks in deserts and can make Earth rocks look like meteorites.
Desiccant storage Explorer: Keeping meteorites in sealed containers with a moisture-absorbing material, such as silica gel, to stop them rusting.
Deuterium-to-hydrogen ratio Enthusiast: The deuterium-to-hydrogen ratio compares heavy hydrogen to ordinary hydrogen and is used to trace the source of water.
Didymos Explorer: Didymos is a near-Earth binary asteroid, about 780 metres across, whose moon Dimorphos was struck by DART.
Differentiation Explorer: The process by which a melted planet or asteroid separates into layers, with heavy metal sinking to form a core and lighter rock floating to form a crust.
Diogenite Enthusiast: An achondrite made mostly of magnesium-rich orthopyroxene, thought to come from deep in the crust of Vesta.
Diopside Expert: Diopside is a calcium-magnesium clinopyroxene found in CAIs, aubrites and many chondrites.
Dolomite Expert: Dolomite is a calcium-magnesium carbonate formed by water inside CI and some CM chondrite parent bodies.
Draconids Explorer: The Draconids are an October meteor shower from Comet Giacobini–Zinner, usually weak but capable of storms.
Dwarf planet Beginner: A dwarf planet is a body that orbits the Sun and is round, but has not cleared its orbit of other objects.

E

Eagle Station pallasite Expert: Eagle Station pallasites are a small pallasite grouplet with more iron-rich olivine and distinctive oxygen isotopes.
Earth's Moon Beginner: The Moon is Earth's natural satellite, about 3,475 kilometres across, and a few hundred meteorites have come from it.
Earthgrazer Enthusiast: A long, slow meteor that skims almost horizontally through the upper atmosphere, often seen when a shower's radiant is near the horizon.
Eccentricity Enthusiast: Eccentricity measures how stretched an orbit is, from 0 for a perfect circle towards 1 for a long, thin ellipse.
Ecliptic Enthusiast: The ecliptic is the path the Sun appears to follow across the sky in a year, marking the plane of Earth's orbit.
EH chondrite Enthusiast: An EH chondrite is an enstatite chondrite with high total iron and small chondrules, formed in very oxygen-poor conditions.
Ejecta Explorer: Rock and debris thrown out of a crater during an impact.
EL chondrite Enthusiast: An EL chondrite is an enstatite chondrite with lower total iron than EH chondrites and often more heating.
Electron microprobe Expert: An electron microprobe is an instrument that fires a focused electron beam at a polished sample and measures the X-rays produced to find the exact chemical composition of tiny spots.
Electrophonic sound Enthusiast: Electrophonic sound is a hiss or crackle heard at the same moment a bright fireball is seen, caused by radio waves.
End cut Explorer: A piece sawn from the end of a meteorite, with one flat cut face and the natural outer surface on the other side.
Enstatite Enthusiast: A magnesium-rich pyroxene that dominates enstatite chondrites and aubrites.
Enstatite chondrite Enthusiast: Enstatite chondrites are highly reduced chondrites made mostly of the iron-poor pyroxene enstatite, formed in an oxygen-starved environment.
Epsilon notation Expert: Epsilon notation expresses very small isotope differences in parts per ten thousand, written ε.
Equilibrated chondrite Enthusiast: An equilibrated chondrite is one heated enough inside its parent asteroid that its main minerals have evened out to nearly the same composition.
Eros Explorer: Eros is a large near-Earth asteroid, about 34 kilometres long, the first asteroid orbited and landed on by a spacecraft.
Escape velocity Explorer: Escape velocity is the speed an object needs to break free of a body's gravity without further push.
Eta Aquariids Explorer: The Eta Aquariids are a May meteor shower from Halley's Comet, best seen from the southern hemisphere.
Etching Enthusiast: Etching is treating a polished iron meteorite surface with weak acid so that its hidden crystal structure, such as the Widmanstätten pattern, becomes visible.
Eucrite Enthusiast: A basaltic achondrite, a frozen lava or shallow intrusive rock from the crust of the asteroid Vesta.
Export rules Enthusiast: Laws that control whether, and how, meteorites can be taken out of the country where they were found.
Exsolution Expert: Exsolution is the separation of one mineral out of another as a crystal cools and can no longer hold its mixed chemistry.
Extinct comet Expert: An extinct comet is a comet that has lost its surface ice or become buried in dust, so it no longer forms a coma.
Extinct radionuclide Expert: An extinct radionuclide is a short-lived radioactive isotope that has entirely decayed but left traces in meteorites.

F

Fake meteorite Explorer: A fake meteorite is an Earth rock or man-made object deliberately sold as a meteorite.
Fall Beginner: A fall is a meteorite that people saw coming down and then collected.
Fall probability Enthusiast: Over a year, an area the size of the UK probably receives a few tens of meteorites, though few are seen or found.
Fast rotator Expert: A fast rotator is an asteroid that spins once in less than about two hours, too fast for a loose rubble pile to hold together.
Fayalite Enthusiast: Fayalite is the iron-rich form of olivine, darker and denser than its magnesium cousin.
Fayalite content (Fa) Expert: Fayalite content (Fa) is the proportion of iron-rich fayalite in a meteorite's olivine, given in mole per cent, and is a key number for classifying chondrites.
Feldspar Beginner: Feldspar is a family of pale silicate minerals rich in aluminium, and the commonest mineral group in Earth's crust.
Feldspathic lunar meteorite Enthusiast: A feldspathic lunar meteorite is a Moon rock rich in plagioclase feldspar, coming from the lunar highlands.
Ferrihydrite Expert: Ferrihydrite is a poorly crystalline iron oxyhydroxide found in CI chondrites and in rusting meteorites.
Find Beginner: A find is a meteorite discovered on the ground without anyone having seen it fall.
Fine-grained rim Expert: A fine-grained rim is a coating of dusty material wrapped around a chondrule or inclusion in a primitive chondrite.
Fireball Beginner: A fireball is an extra-bright meteor, brighter than the planet Venus.
Fireball altitude Explorer: Fireballs usually begin glowing about 80 to 120 kilometres up and end about 20 to 50 kilometres up.
Fireball fragmentation Expert: Fireball fragmentation is the breaking apart of a meteoroid in the air, often seen as sudden flares in brightness.
Fireball network Enthusiast: A fireball network is a group of automatic cameras spread across a region that record bright meteors to calculate their paths and orbits.
Fireball network camera Expert: A fireball network camera is an automated sky camera that records fireballs, timing them precisely for tracking.
Fireball report Beginner: A description of a very bright meteor that a member of the public sends in to help scientists work out its path.
Fireball trajectory Enthusiast: A fireball trajectory is the path of a fireball through the atmosphere, worked out from several camera views.
Flow lines Enthusiast: Flow lines are thin streaks in a meteorite's fusion crust, left by melt that was pushed backwards across the surface during flight.
Flyby Explorer: A flyby is a mission or manoeuvre in which a spacecraft passes close to a body without stopping or orbiting it.
Formation age Enthusiast: The time since a meteorite or its components first formed as solid rock, as opposed to when it travelled through space or landed on Earth.
Forsterite Enthusiast: Forsterite is the magnesium-rich form of olivine, common in chondrules and the oldest dust of the Solar System.
Forward scatter Expert: Forward scatter is a method of detecting meteors by listening for distant radio signals briefly reflected by meteor trails.
Fossil meteorite Expert: A fossil meteorite is a meteorite preserved in ancient rock, whose minerals have mostly been replaced by Earth minerals.
Fossil tracks Expert: Fossil tracks are microscopic trails of damage left in crystals by heavy cosmic-ray nuclei or fission fragments.
Fractional crystallisation Expert: Fractional crystallisation is the step-by-step change in a magma's chemistry as early crystals form and are removed.
Fragmental breccia Expert: A fragmental breccia consists of rock and mineral fragments in a matrix of finer crushed debris, with no melt binding them.
Fragmentation Explorer: Fragmentation is the breaking up of a meteoroid into many pieces as it passes through the atmosphere.
Fusion crust Beginner: Fusion crust is the thin, dark skin that forms on a meteorite as its surface melts during its fall.
Fusion crust colour Explorer: Fresh fusion crust is usually black and may be matte or glossy; it turns brown as the meteorite weathers.

G

Gas retention age Expert: A gas retention age is the time since a rock last became cold enough to hold radiogenic helium or argon.
Geminids Beginner: The Geminids are a rich meteor shower each December, produced by debris from the asteroid Phaethon.
Genesis mission Expert: Genesis was a NASA mission that collected solar wind particles and returned them to Earth in 2004.
Genomict breccia Expert: A genomict breccia contains fragments of the same meteorite group but of different petrologic types or textures.
Geostationary Lightning Mapper Expert: The Geostationary Lightning Mapper is a weather-satellite camera that records lightning and also detects bright fireballs.
Giant impact hypothesis Enthusiast: The giant impact hypothesis says the Moon formed from debris after a Mars-sized body struck the young Earth.
Giotto Explorer: Giotto was a European spacecraft that flew past Halley's Comet in 1986 and took the first close images of a comet's nucleus.
Glass Explorer: Glass is a solid with no crystal structure, formed when melted material cools too fast for crystals to grow.
Goethite Explorer: Goethite is an iron oxyhydroxide that forms the brown rust on weathered meteorites.
GPS recording Beginner: GPS recording means noting the exact position where a meteorite is found, which makes it far more useful to science.
Graphite Enthusiast: A soft, black form of carbon found as nodules in some iron meteorites and as seams in ureilites.
Gravity assist Enthusiast: A gravity assist uses a planet's gravity during a flyby to change a spacecraft's speed and direction without fuel.
Grouplet Expert: A grouplet is a small set of related meteorites, usually fewer than five, too few to define a formal group.
Gypsum Enthusiast: Gypsum is a calcium sulfate mineral seen as veins in some CI chondrites, partly formed after they reached Earth.

H

H chondrite Enthusiast: H chondrites are ordinary chondrites with the highest content of iron and metal.
Hafnium–tungsten dating Expert: A dating method based on the extinct isotope hafnium-182, used to time metal–silicate separation and core formation in early planetesimals and planets.
Half-life Explorer: The time it takes for half of the atoms of a radioactive isotope in a sample to decay.
Halley's Comet Beginner: Halley's Comet is a famous comet that returns about every 76 years and is the parent of two meteor showers.
Hand lens Beginner: A small folding magnifying glass, usually making things look ten times bigger, that you hold close to your eye to inspect rocks.
Hand specimen Explorer: A hand specimen is a piece of rock or meteorite large enough to hold and examine by eye or with a hand lens.
Haxonite Expert: Haxonite is an iron-nickel carbide found in some iron meteorites and in metal grains of primitive chondrites.
Hayabusa Enthusiast: Hayabusa was a Japanese mission that brought back the first samples from an asteroid, Itokawa, in 2010.
Hayabusa2 Enthusiast: Hayabusa2 was a Japanese mission that returned about 5.4 grams of rock from the carbon-rich asteroid Ryugu in 2020.
Hayabusa2 extended mission Expert: After returning Ryugu samples, Hayabusa2 continued on an extended mission to fly past one asteroid and rendezvous with another by 2031.
Heat-affected zone Enthusiast: The heat-affected zone is a thin layer just beneath a meteorite's fusion crust whose structure was altered by the heat of atmospheric entry.
HED meteorites Enthusiast: The related family of howardites, eucrites and diogenites, thought to come from the asteroid Vesta.
Hematite Explorer: Hematite is a common iron oxide mineral that is heavy and dark and is often mistaken for a meteorite, but it leaves a red-brown streak.
Hera Enthusiast: Hera is a European mission launched in 2024 to study the Didymos asteroid pair after DART's impact.
Hexahedrite Enthusiast: An iron meteorite low in nickel, made of large kamacite crystals and showing no Widmanstätten pattern.
Hibonite Expert: Hibonite is a calcium-aluminium oxide among the first minerals to condense in the young Solar System.
High-pressure mineral Enthusiast: A high-pressure mineral is a denser form of a common mineral, created when a collision squeezes rock to extreme pressures.
Hot desert meteorite Explorer: A meteorite found in a hot, dry desert such as the Sahara, where little rain and few plants help rocks survive and stand out.
Howardite Explorer: A stony meteorite made of broken pieces of eucrite and diogenite rock, glued together on the surface of the asteroid Vesta.
Hubble Space Telescope Beginner: The Hubble Space Telescope is a large telescope orbiting Earth since 1990, which has studied asteroids, comets and many other objects.
Hydrocode Expert: A hydrocode is a computer program that simulates the shock waves, melting and flow of material during impacts.
Hypervelocity impact Enthusiast: A collision so fast that the object hits faster than sound can travel through rock, making the impact behave like an explosion.

I

IAB complex Expert: A large, chemically scattered family of iron meteorites, many carrying silicate, graphite and sulfide inclusions.
IC irons Expert: IC irons are a small magmatic group of iron meteorites, low in nickel and often coarse in structure.
Ice field stranding zone Expert: A stranding zone is a blue-ice area in Antarctica where flowing ice carries meteorites to the surface and concentrates them.
Iddingsite Enthusiast: Iddingsite is a reddish mixture of clay and iron oxides formed when water altered olivine, notably in Martian nakhlites.
Igneous rock Explorer: An igneous rock forms when molten rock cools and solidifies, such as basalt or the eucrite meteorites.
IIAB irons Expert: A magmatic iron-meteorite group of low-nickel hexahedrites and coarsest octahedrites.
IIC irons Expert: IIC irons are a small group of plessitic octahedrites rich in nickel and gallium relative to their structure.
IID irons Expert: IID irons are a magmatic group of medium to fine octahedrites rich in gallium and germanium.
IIE irons Expert: A non-magmatic iron group containing silicate inclusions related to H chondrites.
IIIAB irons Expert: The largest group of iron meteorites, mostly medium octahedrites formed in a once-molten asteroid core.
IIIE irons Expert: IIIE irons are a small group of coarse octahedrites closely related to IIIAB irons but containing haxonite.
Ilmenite Enthusiast: Ilmenite is an iron-titanium oxide that is abundant in some lunar basalts and present in many igneous meteorites.
Impact angle Enthusiast: Impact angle is the angle between an impactor's path and the ground; the most likely angle is 45 degrees.
Impact basin Enthusiast: An impact basin is a very large impact crater, usually more than about 300 kilometres across on the Moon.
Impact crater Beginner: A hole blasted in the surface of a planet, moon or asteroid when a fast-moving object from space crashes into it.
Impact energy Explorer: Impact energy is the energy of motion an asteroid or meteoroid carries, released when it hits a planet or its atmosphere.
Impact glass Enthusiast: Glass made when the heat and pressure of an impact melt rock so fast that it cools before crystals can grow.
Impact melt Enthusiast: Rock that was melted by the heat and pressure of an impact, then cooled to form glass or crystalline rock.
Impact melt breccia Expert: An impact melt breccia is a rock in which fragments are held in a matrix of rock melted by an impact.
Impact spherule Enthusiast: An impact spherule is a tiny droplet of melted rock thrown out by a large impact, which can travel around the world.
Impact structure Enthusiast: An impact structure is the remains of an impact crater, often eroded or buried so that the original bowl is no longer visible.
Impactite Enthusiast: Any rock created or changed by a meteorite impact, including shocked rocks, impact breccias, impact melt rocks and impact glasses.
Inclination Enthusiast: Inclination is the angle by which an orbit is tilted compared with Earth's orbital plane.
Individual Explorer: An individual is a complete meteorite that landed as a separate piece, usually crusted all over.
Infrasound Enthusiast: Infrasound is sound too low for humans to hear, which large fireballs produce and distant sensors can detect.
Ingenuity helicopter Beginner: Ingenuity was a small NASA helicopter that made the first powered flights on another planet, on Mars, from 2021 to 2024.
Interplanetary dust particle Expert: An interplanetary dust particle (IDP) is a microscopic grain of cosmic dust collected in Earth's upper atmosphere before it reaches the ground.
Interstellar object Enthusiast: An object passing through the Solar System that came from outside it, from the space between the stars.
Iodine–xenon dating Expert: Iodine–xenon dating uses the extinct isotope iodine-129, which decayed to xenon-129, to date early events.
Ion probe Expert: An ion probe fires a narrow beam of ions at a polished sample and measures the isotopes knocked out of a tiny spot.
Iridium anomaly Enthusiast: A layer of rock with far more of the rare metal iridium than normal, often a sign that an asteroid impact scattered its debris worldwide.
Iron meteorite Beginner: An iron meteorite is made mostly of iron and nickel metal.
Iron-60 Expert: Iron-60 is a short-lived radioactive isotope made in massive stars; its amount in the early Solar System is debated.
Iron-nickel metal Beginner: The shiny metal found in most meteorites, made of iron mixed with a little nickel.
Isochron Expert: A straight-line plot of isotope ratios measured in several cogenetic samples, whose slope gives an age and whose intercept gives the initial isotopic composition.
Isotope Explorer: One of two or more forms of the same chemical element whose atoms have different numbers of neutrons, and so different masses.
Isotopic dichotomy Expert: The isotopic dichotomy is the split of meteorites into two isotopic families, non-carbonaceous and carbonaceous, from the inner and outer Solar System.
Itokawa Enthusiast: A small, peanut-shaped near-Earth asteroid visited by Japan's Hayabusa spacecraft, which brought the first asteroid samples back to Earth.
IVA irons Expert: A magmatic iron group of fine octahedrites, low in gallium and germanium, with puzzlingly varied cooling rates.
IVB irons Expert: A small magmatic iron group of nickel-rich ataxites, very depleted in volatile elements.

J

James Webb Space Telescope Explorer: The James Webb Space Telescope is a large infrared space telescope launched in 2021, able to study the chemistry of asteroids and comets.
Jarosite Expert: Jarosite is a potassium iron sulfate that forms in acidic water, found in some Martian meteorites and on Mars itself.
Jupiter Beginner: Jupiter is the largest planet in the Solar System, whose gravity shapes the asteroid belt and steers meteoroids towards Earth.
Jupiter-family comet Enthusiast: A Jupiter-family comet is a comet with an orbital period of less than about 20 years, controlled by Jupiter's gravity.

K

K–Pg boundary Explorer: The thin layer of rock that marks the end of the Cretaceous period 66 million years ago, when a giant asteroid impact helped wipe out the dinosaurs.
Kakangari chondrite Expert: Kakangari chondrites, or K chondrites, are a small grouplet with chemistry and oxygen isotopes unlike other chondrite classes.
Kamacite Enthusiast: The nickel-poor form of iron-nickel metal in meteorites, forming the broad bands of the Widmanstätten pattern.
Kamacite bandwidth Enthusiast: Kamacite bandwidth is the width of the kamacite plates in an octahedrite, used to sort them from coarsest to finest.
Kilotonne of TNT Explorer: A kilotonne of TNT is a unit of energy equal to the explosion of 1,000 tonnes of TNT, used to describe impacts and airbursts.
Kirkwood gaps Expert: Narrow zones in the main asteroid belt with very few asteroids, cleared by orbital resonances with Jupiter.
Kosmochlor Expert: Kosmochlor is a bright green sodium-chromium pyroxene first discovered in iron meteorites.
KREEP Expert: KREEP is lunar material rich in potassium, rare earth elements and phosphorus, left over from the Moon's magma ocean.
Kuiper Belt Explorer: A huge ring of icy bodies beyond Neptune, including the dwarf planet Pluto.
Kuiper Belt object Explorer: A Kuiper Belt object is an icy body orbiting beyond Neptune in the Kuiper Belt, such as Pluto or Arrokoth.

L

L chondrite Enthusiast: L chondrites are ordinary chondrites with a lower iron and metal content than H chondrites.
Lagrange point Expert: A Lagrange point is a spot where the gravity of two large bodies balances so that a small object can stay in step with them.
Lander Explorer: A lander is a spacecraft designed to touch down on the surface of a planet, moon, asteroid or comet.
Landowner permission Beginner: Asking the person who owns or manages a piece of land before you go onto it to look for meteorites.
Lawrencite Enthusiast: Lawrencite is iron chloride, long blamed for making meteorites rust and crumble, though its role is now doubted.
Lead–lead dating Expert: A radiometric method that uses the ratio of two lead isotopes produced by two uranium decay chains to obtain very precise ages.
Leonids Explorer: The Leonids are a November meteor shower from Comet Tempel–Tuttle, famous for occasional spectacular storms.
Libyan Desert Glass Enthusiast: Libyan Desert Glass is a pale yellow natural glass found in the Sahara, formed by intense heat about 29 million years ago.
Light pollution Beginner: Unwanted artificial light that brightens the night sky and hides the stars and meteors.
Light-year Beginner: A light-year is the distance light travels in a year, about 9.46 trillion kilometres.
Limiting magnitude Enthusiast: The brightness of the faintest stars you can see, which shows how dark and clear your sky is.
Lithophile element Expert: A lithophile element prefers to sit in silicate rock rather than metal or sulfide, such as calcium, aluminium and potassium.
LL chondrite Enthusiast: LL chondrites are ordinary chondrites with the least iron and metal of the three groups.
Lodranite Expert: Lodranites are coarse-grained primitive achondrites that lost some of their metal–sulfide and basaltic melts.
Long-period comet Enthusiast: A long-period comet takes more than 200 years to orbit the Sun and comes from the distant Oort Cloud.
Lonsdaleite Expert: A form of carbon reported from meteorites and impact sites, described as hexagonal diamond.
Lucy mission Enthusiast: Lucy is a NASA mission launched in 2021 to fly past several Trojan asteroids that share Jupiter's orbit.
Luna samples Enthusiast: Luna samples are the small amounts of lunar soil brought back by three Soviet robotic missions between 1970 and 1976.
Lunar meteorite Beginner: A rock knocked off the Moon by an impact that later fell to Earth.
Lyrids Explorer: The Lyrids are an April meteor shower from Comet Thatcher, one of the oldest recorded showers.

M

M-type asteroid Explorer: An M-type asteroid has a moderately bright, featureless spectrum, and some are thought to be rich in metal.
Mafic Enthusiast: Mafic describes rock or minerals rich in magnesium and iron, such as basalt, olivine and pyroxene.
Magma ocean Enthusiast: A magma ocean is a deep global layer of molten rock thought to have covered the young Moon and possibly other bodies.
Magmatic iron Expert: An iron meteorite from a group whose chemistry records fractional crystallisation of a molten metal core.
Magnet test Beginner: The magnet test checks whether a rock is attracted to a magnet, because most meteorites contain iron metal.
Magnetite Explorer: A black, strongly magnetic iron oxide found in some meteorites and in many Earth rocks that are mistaken for meteorites.
Main mass Explorer: The main mass is the largest single piece recovered from a meteorite.
Main-belt comet Expert: A main-belt comet is an object in the asteroid belt that shows comet-like activity from ice turning to gas.
Main-group pallasite Enthusiast: Main-group pallasites are the largest pallasite group, with olivine crystals set in metal similar to IIIAB irons.
Majorite Expert: Majorite is a high-pressure garnet formed from pyroxene in strongly shocked meteorites.
Manganese–chromium dating Expert: Manganese–chromium dating uses the extinct isotope manganese-53, decaying to chromium-53, to date early processes.
Mare basalt Enthusiast: Mare basalt is the dark volcanic rock that fills the Moon's large lowland plains, the maria.
Mars Beginner: Mars is the fourth planet from the Sun, a cold, rocky world with ancient river valleys; some meteorites come from it.
Mars Sample Return Enthusiast: Mars Sample Return is a planned campaign to bring back rock cores collected by NASA's Perseverance rover.
Martensite Expert: Martensite is a hard, needle-like form of iron-nickel metal produced when taenite is cooled very quickly.
Martian meteorite Beginner: A rock that was blasted off Mars by an impact and later landed on Earth.
Maskelynite Expert: Plagioclase feldspar turned into glass by intense shock, while keeping the shape of the original crystals.
Mass spectrometer Enthusiast: A mass spectrometer is an instrument that separates atoms or molecules by mass to measure isotopes and elements.
Mass-dependent fractionation Expert: Mass-dependent fractionation is the sorting of isotopes by mass during processes such as evaporation and diffusion.
Mass-independent fractionation Expert: Mass-independent fractionation is isotope separation that does not follow simple mass rules, as seen in oxygen isotopes of meteorites.
Matrix Explorer: Matrix is the fine-grained material that fills the spaces between the larger grains in a meteorite, like the cement between pebbles.
Melilite Expert: Melilite is a calcium-aluminium-magnesium silicate that is a main mineral of many CAIs.
Melt pocket Expert: A melt pocket is a small patch of glass or fine crystals formed by local melting during a shock event.
Mercury Beginner: Mercury is the smallest planet and the closest to the Sun, heavily cratered and with a huge iron core.
Merrillite Expert: Merrillite is a calcium phosphate mineral common in meteorites and lunar rocks but almost unknown on Earth.
Mesosiderite Enthusiast: A stony-iron breccia made of iron-nickel metal mixed with broken basaltic and pyroxene-rich rock.
Mesostasis Expert: Mesostasis is the glassy or finely crystalline material filling the spaces between larger crystals in a chondrule or igneous rock.
Metal detector Explorer: An electronic device that senses metal buried in the ground and is used to find iron meteorites and metal-rich stones.
Metal flecks Beginner: Metal flecks are small shiny grains of iron-nickel metal visible on cut or broken surfaces of most stony meteorites.
Metallographic cooling rate Expert: A metallographic cooling rate is estimated from the way nickel is distributed in kamacite and taenite in meteoritic metal.
Meteor Beginner: A meteor is the streak of light you see when a meteoroid burns up in Earth's air.
Meteor colour Beginner: Meteors can glow green, orange, blue or red, depending on their speed, chemistry and the air they heat.
Meteor head echo Expert: A meteor head echo is a radar reflection from the cloud of plasma moving with a meteoroid, used to measure its speed.
Meteor photography Explorer: Meteor photography uses a camera on a tripod taking long exposures of the sky to catch meteors by chance.
Meteor rate Explorer: Meteor rate is the number of meteors seen per hour, which varies with the shower, sky darkness and time of night.
Meteor shower Beginner: A time each year when many more shooting stars than usual can be seen, all seeming to come from the same part of the sky.
Meteor spectrum Expert: A meteor spectrum is the light of a meteor split into colours, revealing which elements are glowing.
Meteor storm Explorer: An extraordinary display in which a meteor shower produces a thousand or more meteors an hour.
Meteor train Explorer: A meteor train is the glowing trail left behind after a meteor has passed, lasting from a fraction of a second to many minutes.
Meteor watching Beginner: Meteor watching needs no equipment, just a dark, open sky, warm clothes, patience and safety.
Meteorite Beginner: A meteorite is a piece of space rock that has survived its fall through the air and landed on Earth.
Meteorite dealer Explorer: A meteorite dealer buys and sells meteorites; good ones give clear names, classifications and provenance.
Meteorite hunter Beginner: A person who searches for meteorites on the ground, often after a bright fireball has been seen.
Meteorite name Explorer: A meteorite name is its official label, usually taken from the place where it fell or was found.
Meteorite ownership Explorer: The question of who legally owns a meteorite, which depends on where it landed and on the laws of that country.
Meteorite recovery Explorer: Meteorite recovery is the search for and collection of meteorites after a fall, or of finds in deserts and on ice.
Meteoritic diamond Enthusiast: Diamond found in meteorites, from tiny grains made around other stars to shock- or pressure-formed crystals.
Meteoritical Bulletin Enthusiast: The Meteoritical Bulletin is the Meteoritical Society's official record of newly approved meteorites, their names and their classifications.
Meteoroid Beginner: A meteoroid is a small piece of rock or metal travelling through space.
Meteoroid stream Enthusiast: A trail of dust and small particles spread along the orbit of a comet or asteroid, which produces a meteor shower when Earth passes through it.
Meteorwrong Beginner: A meteorwrong is an Earth rock or object that someone mistakes for a meteorite.
Micrometeorite Explorer: A micrometeorite is a tiny particle of space dust, usually smaller than a millimetre, that has reached Earth's surface.
Micromount Enthusiast: A tiny specimen fixed in a small box so it can be studied under magnification.
Mineral Beginner: A mineral is a natural solid with a fixed chemical recipe and an orderly inner arrangement of atoms.
Minimoon Enthusiast: A minimoon is a small asteroid temporarily captured into orbit around Earth for a few months or years.
Minor Planet Center Enthusiast: The Minor Planet Center is the international clearing house that collects observations and orbits of asteroids and comets.
MMX Expert: MMX is a planned Japanese mission to the Martian moons, aiming to return samples from Phobos.
Moissanite Expert: Moissanite is natural silicon carbide; meteoritic grains of it are among the best-studied stardust older than the Sun.
Moldavite Explorer: A bottle-green natural glass from the Czech Republic, made when an asteroid struck southern Germany about 15 million years ago.
Moldavite fakes Enthusiast: Moldavite fakes are pieces of green glass made to imitate moldavite, a natural tektite from central Europe.
Monomict breccia Expert: A monomict breccia is made of broken fragments of a single rock type, crushed and reassembled.
Moonlight Beginner: Moonlight brightens the night sky and can hide fainter meteors, so the Moon's phase matters for meteor watching.
Mosaicism Expert: Mosaicism is the breaking of a crystal into many slightly misaligned domains by intense shock.
Multi-ring basin Enthusiast: A huge impact structure surrounded by several concentric rings of mountains or cliffs.
Museum collection Beginner: The meteorites a museum keeps, studies and shows to visitors, so everyone can learn from them.

N

Nakhlite Enthusiast: A Martian meteorite made mainly of augite pyroxene crystals, formed in a lava flow or shallow intrusion on Mars.
NEAR Shoemaker Enthusiast: NEAR Shoemaker was the first spacecraft to orbit and land on an asteroid, 433 Eros, in 2000 and 2001.
Near-Earth asteroid Explorer: An asteroid whose orbit brings it fairly close to Earth's path around the Sun.
Near-Earth object Explorer: A near-Earth object is an asteroid or comet whose orbit brings it to within about 1.3 au of the Sun.
NEO Surveyor Expert: NEO Surveyor is a planned NASA infrared space telescope designed to find most of the hazardous near-Earth asteroids.
Neumann lines Enthusiast: Fine, straight parallel lines in kamacite caused by shock twinning, seen on etched iron meteorites.
New Horizons Explorer: New Horizons is a NASA spacecraft that flew past Pluto in 2015 and Arrokoth in 2019.
Nickel test Enthusiast: A nickel test is a chemical spot test that turns pink if nickel is present, helping to tell meteoritic metal from most man-made iron.
Nickel, gallium and germanium Expert: Nickel, gallium and germanium are the three elements whose concentrations, plotted against each other, classically define the chemical groups of iron meteorites.
Niningerite Expert: Niningerite is a magnesium-rich sulfide found in EH enstatite chondrites, a sign of very oxygen-poor formation.
Noble gases Enthusiast: Noble gases are the unreactive gases helium, neon, argon, krypton and xenon, whose isotopes record many events in a meteorite's history.
Nomenclature Committee Enthusiast: The Nomenclature Committee is the group of scientists within the Meteoritical Society that approves official meteorite names and classifications.
Northwest Africa (NWA) Enthusiast: A naming label, NWA plus a number, used for meteorites from north-western Africa whose exact find locations are not known.
Nucleosynthesis Enthusiast: Nucleosynthesis is the making of new atomic nuclei, in the Big Bang, in stars and in stellar explosions.
Nucleosynthetic anomaly Expert: A nucleosynthetic anomaly is a small isotopic difference inherited from material made in different stars.

O

Octahedrite Enthusiast: The most common structural class of iron meteorite, showing a criss-cross Widmanstätten pattern when etched.
Oldhamite Expert: A calcium sulfide mineral, CaS, found in enstatite chondrites and aubrites, which reacts readily with moisture.
Olivine Beginner: A green mineral that is very common in meteorites and makes the gem called peridot.
Olivine-phyric shergottite Expert: An olivine-phyric shergottite is a Martian basalt containing large olivine crystals in a finer groundmass.
Oort Cloud Explorer: A vast, distant shell of icy objects thought to surround the Solar System and send long-period comets towards the Sun.
Orbit Beginner: An orbit is the curved path one object follows around another under gravity, such as Earth around the Sun.
Orbital elements Enthusiast: Orbital elements are the six numbers that describe the size, shape and orientation of an orbit and where an object is on it.
Orbital resonance Enthusiast: A repeating gravitational nudge that happens when two bodies' orbital periods form a simple ratio, such as 2:1 or 3:2.
Orbiter Explorer: An orbiter is a spacecraft that goes into orbit around a planet, moon or asteroid to study it for a long time.
Ordinary chondrite Explorer: Ordinary chondrites are the most common meteorites, divided into H, L and LL groups by how much iron they contain.
Organic matter Enthusiast: Organic matter in meteorites is carbon-based chemistry, made without life, that ranges from simple molecules to large, tar-like solids.
Oriented meteorite Explorer: An oriented meteorite is one that kept the same face forward during its fall, giving it a cone or shield shape.
Orionids Explorer: The Orionids are an October meteor shower produced by dust from Halley's Comet.
Orthopyroxene Enthusiast: Orthopyroxene is a group of pyroxene minerals with an orthorhombic crystal structure, typically low in calcium.
Orthopyroxenite Expert: An orthopyroxenite is a rock made almost entirely of orthopyroxene, such as the Martian meteorite ALH 84001.
OSIRIS-REx Enthusiast: OSIRIS-REx was a NASA mission that returned about 122 grams of material from asteroid Bennu in 2023.
Outburst Enthusiast: A sudden, short-lived rise in a meteor shower's activity well above its normal level.
Oxide Explorer: An oxide is a mineral in which a metal is combined directly with oxygen, such as chromite or magnetite.
Oxygen isotopes Expert: Oxygen isotopes are the three stable forms of oxygen, whose ratios in a meteorite act like a fingerprint for its parent body.

P

Pairing Enthusiast: Pairing is recognising that meteorites recovered and named separately are actually pieces of the same fall.
Paleometeorite Expert: A paleometeorite is a meteorite that fell to Earth in the distant geological past and has been preserved in rock.
Pallasite Explorer: A stony-iron meteorite with green olivine crystals set in a network of shiny iron-nickel metal.
Parent and daughter isotopes Explorer: In radioactive decay, the parent isotope is the one that decays and the daughter isotope is the one it turns into.
Parent body Explorer: The asteroid, moon or planet that a meteorite was originally part of before it was knocked off into space.
Partial melting Expert: Partial melting is when only part of a rock melts, producing a melt with a different composition from the solid left behind.
Peak ring Enthusiast: A circle of mountains inside a large impact crater, found instead of a single central peak.
Pentlandite Expert: Pentlandite is an iron-nickel sulfide found in carbonaceous chondrites and some ordinary chondrites.
Perihelion Explorer: Perihelion is the point in an orbit where an object comes closest to the Sun.
Perovskite Expert: Perovskite is a calcium-titanium oxide found as tiny grains in CAIs, one of the earliest condensates.
Perseids Beginner: The Perseids are a popular summer meteor shower each August, made by dust from Comet Swift–Tuttle.
Perseverance rover Explorer: Perseverance is a NASA rover exploring Jezero crater on Mars since 2021 and collecting rock samples.
Persistent train Enthusiast: A faint glowing trail left behind by some bright meteors that stays visible for seconds, minutes or occasionally longer.
Petrologic subtype Expert: Petrologic subtypes divide type 3 chondrites from 3.00 to 3.9 according to how much heating they experienced.
Petrologic type Enthusiast: The petrologic type is a number from 1 to 7 added to a chondrite's group to show how much it was altered by water or heat on its parent body.
Phaethon Enthusiast: 3200 Phaethon is a near-Earth asteroid that is the parent of the Geminid meteor shower.
Philae Explorer: Philae was the small lander from the Rosetta mission that made the first landing on a comet in November 2014.
Phobos Explorer: Phobos is the larger of Mars's two small moons, a dark, cratered body about 22 kilometres across.
Phosphate Explorer: A phosphate is a mineral containing phosphorus bonded to oxygen, such as apatite and merrillite.
Phyllosilicate Expert: A sheet-structured silicate, such as serpentine or clay, formed in meteorites when water altered the rock.
Pigeonite Expert: Pigeonite is a low-calcium clinopyroxene that forms in quickly cooled basalts and is a hallmark of eucrites.
Plagioclase Explorer: A feldspar mineral, rich in calcium or sodium, that forms the pale grains in many achondrites and lunar rocks.
Planar deformation features Expert: Sets of very thin, straight, parallel lamellae of amorphous material in minerals such as quartz, formed by shock and diagnostic of impact.
Planar fractures Expert: Planar fractures are sets of parallel cracks in crystals formed by moderate shock.
Planet Beginner: A planet is a large, round body orbiting a star that has cleared its path of most other material.
Planetary defence Explorer: Finding, tracking and, if needed, deflecting asteroids and comets that might hit Earth.
Planetesimal Enthusiast: One of the countless small bodies, from about a kilometre to a few hundred kilometres across, that collided and merged to build the planets.
Plessite Expert: A fine-grained intergrowth of kamacite and taenite filling the spaces between Widmanstätten bands.
Pluto Beginner: Pluto is a dwarf planet in the Kuiper Belt, about 2,377 kilometres across, with ice mountains and a thin atmosphere.
Poikilitic shergottite Expert: A poikilitic shergottite is a Martian rock in which large pyroxene crystals enclose many smaller olivine grains.
Polarising microscope Enthusiast: A polarising microscope uses polarised light to identify minerals in thin rock slices by their colours and how they change as the slide is rotated.
Polymict breccia Enthusiast: A polymict breccia is a rock made of broken fragments of several different rock types cemented together.
Polymict eucrite Expert: A polymict eucrite is a breccia of different eucrite rocks with less than 10 per cent diogenite.
Porphyritic chondrule Enthusiast: A porphyritic chondrule contains large crystals of olivine or pyroxene set in fine-grained material or glass.
Potassium–argon dating Enthusiast: Potassium–argon dating measures argon-40 produced by the decay of potassium-40 to find when a rock last cooled.
Potentially hazardous asteroid Explorer: A fairly large asteroid whose orbit comes close enough to Earth's that it needs careful watching.
Pre-atmospheric size Enthusiast: Pre-atmospheric size is the size of a meteoroid before it entered Earth's atmosphere and lost material to ablation and break-up.
Predicted impact Enthusiast: A predicted impact is an asteroid strike on Earth forecast after the asteroid was spotted in space beforehand.
Presolar grains Expert: Presolar grains are microscopic dust particles that formed around other stars before the Sun existed and survived inside primitive meteorites.
Primitive achondrite Expert: Primitive achondrites are meteorites that were heated enough to recrystallise and partly melt, but still keep near-chondritic bulk compositions.
Protoplanetary disc Enthusiast: A flattened, spinning disc of gas and dust around a young star, where planets form.
Provenance Enthusiast: The documented history of a meteorite specimen, from where and when it was found to every owner it has passed through.
Psyche Explorer: 16 Psyche is a large, metal-rich asteroid about 220 kilometres across, target of NASA's Psyche mission.
Psyche mission Enthusiast: Psyche is a NASA mission launched in 2023 to orbit the metal-rich asteroid 16 Psyche.
Public land Enthusiast: Public land is land owned by a government; collecting meteorites on it is often restricted or needs a permit.
Pyroxene Explorer: A family of common rock-forming minerals made of silicon and oxygen chains, important in almost all stony meteorites.
Pyroxene pallasite Expert: Pyroxene pallasites are a tiny grouplet of pallasites that contain pyroxene as well as olivine in their metal.
Pyrrhotite Expert: Pyrrhotite is a slightly iron-deficient iron sulfide, often magnetic, found in carbonaceous chondrites and Martian meteorites.

Q

Quadrantids Explorer: The Quadrantids are an early January meteor shower with a short, sharp peak, named after an old constellation.
Quartz Beginner: Quartz is the common, hard form of silica that is abundant on Earth but rare in meteorites.
Quasi-satellite Expert: A quasi-satellite is an asteroid that orbits the Sun in step with a planet, appearing to loop around the planet.

R

R chondrite Expert: R chondrites are highly oxidised, metal-poor chondrites rich in iron-bearing olivine, with distinctive oxygen isotopes.
Radial pyroxene chondrule Enthusiast: A radial pyroxene chondrule has thin pyroxene crystals fanning out from one or more points, like the spokes of a wheel.
Radiant Beginner: The point in the sky that all the meteors in a shower seem to fly out from.
Radio meteor detection Enthusiast: Detecting meteors by catching radio signals that bounce off the trails of electrified air they leave behind.
Radioactive isotope Explorer: A radioactive isotope has an unstable nucleus that decays into another isotope at a steady, measurable rate.
Radiometric dating Explorer: A way of finding the age of a rock by measuring how much of a radioactive element has turned into another element.
Rampart crater Expert: A rampart crater has ejecta that flowed outwards like mud, ending in a raised ridge, common on Mars.
Ray crater Explorer: A ray crater has bright streaks of ejecta radiating outwards, a sign that it is relatively young.
Recrystallisation Enthusiast: Recrystallisation is the slow regrowth of crystals in a solid rock when it is heated without melting.
Refractory element Expert: A refractory element condenses into solid minerals at very high temperatures, such as calcium, aluminium and titanium.
Reg Expert: A reg is a flat, stony desert plain, an ideal surface for spotting and preserving meteorites.
Regmaglypts Explorer: Regmaglypts are shallow dents, like thumbprints, scooped into a meteorite's surface during its fiery fall.
Regolith breccia Enthusiast: A rock formed when loose surface soil on an airless body was pressed into solid stone.
Rheasilvia Enthusiast: Rheasilvia is an enormous impact basin, about 500 kilometres across, near Vesta's south pole and the likely source of many HED meteorites.
Rhenium–osmium dating Expert: Rhenium–osmium dating uses the decay of rhenium-187 to osmium-187 and is ideal for iron meteorites.
Ringwoodite Expert: A high-pressure form of olivine with a spinel structure, found in the shock veins of meteorites.
Rollover lip Expert: A rollover lip is a rim of melted crust that flowed over the edge onto the back of an oriented meteorite.
Rosetta Enthusiast: Rosetta was a European mission that orbited comet 67P/Churyumov–Gerasimenko from 2014 to 2016 and landed a probe on it.
Rubble pile Enthusiast: An asteroid made of many loose rocks and boulders held together only by their own weak gravity, rather than one solid lump.
Rubidium–strontium dating Expert: Rubidium–strontium dating uses the slow decay of rubidium-87 to strontium-87, usually with an isochron.
Rust bloom Explorer: Rust bloom is the patchy orange-brown rust that can break out on iron meteorites and metal-rich stones while they are being stored.
Ryugu Enthusiast: A dark, carbon-rich near-Earth asteroid shaped like a spinning top, sampled by Japan's Hayabusa2 mission.

S

S-type asteroid Explorer: An S-type asteroid is a stony asteroid of moderate brightness, the kind that supplies most ordinary chondrites.
Samarium–neodymium dating Expert: Samarium–neodymium dating uses the decay of samarium-147 to neodymium-143, well suited to igneous meteorites.
Sample return mission Explorer: A space mission that collects material from another world and brings it back to Earth for study.
Saponite Expert: Saponite is a clay mineral that, with serpentine, makes up much of CI chondrites and the Ryugu samples.
Satellite fireball detection Expert: Satellites designed for other purposes, such as lightning or missile detection, also spot large fireballs from orbit.
Satellite trail Explorer: A satellite trail is a line on a night-sky photograph left by sunlight reflecting off an orbiting satellite.
Scanning electron microscope Expert: An instrument that scans a finely focused beam of electrons across a sample to build highly magnified images and chemical maps.
Schreibersite Enthusiast: An iron-nickel phosphide mineral found in iron meteorites, often as bright plates or needles in the metal.
Secondary crater Expert: A secondary crater is made by a block thrown out of a larger impact crater, not by an object from space.
Secondary crust Expert: Secondary crust is a thinner fusion crust formed on surfaces exposed when a meteoroid broke apart late in its flight.
Serpentine Enthusiast: Serpentine is a water-bearing sheet silicate formed when water altered rock on carbonaceous chondrite parent bodies.
Shatter cone Enthusiast: A cone-shaped rock fracture with fanning, horsetail-like grooves, formed by the shock wave of a meteorite impact.
Shergottite Enthusiast: The most common kind of Martian meteorite: a basaltic or olivine-rich volcanic rock from Mars.
Shielding depth Expert: Shielding depth is how deep inside a meteoroid a sample sat, which affects how many cosmogenic nuclides it contains.
Shock darkening Expert: Shock darkening is the blackening of a chondrite when an impact forces tiny droplets of metal and sulfide into its silicate grains.
Shock stage Enthusiast: The shock stage is a grade, usually S1 to S6, describing how strongly a meteorite was shocked by impacts on its parent body.
Shock vein Enthusiast: A shock vein is a thin, dark streak of rock that melted for an instant when a powerful impact shock wave passed through a meteorite's parent body.
Shocked quartz Enthusiast: Quartz whose crystal structure carries microscopic damage that only the extreme pressures of an impact can produce.
Shoemaker–Levy 9 Explorer: Shoemaker–Levy 9 was a comet that broke apart and crashed into Jupiter in July 1994.
Short-lived radionuclide Expert: A short-lived radionuclide has a half-life of millions of years or less and was present only in the early Solar System.
Siderophile element Enthusiast: A siderophile element prefers to dissolve in iron metal, such as nickel, cobalt, iridium, platinum and gold.
Silica Explorer: Silica is silicon dioxide, which forms quartz, cristobalite, tridymite and other minerals and glasses.
Silicate Beginner: A silicate is a mineral built around silicon and oxygen, the main ingredient of rocky planets and stony meteorites.
Silicate inclusion Expert: A silicate inclusion is a piece of stony material enclosed in the metal of an iron meteorite.
Simple crater Explorer: A small, bowl-shaped impact crater with a smooth, rounded floor and no central mountain.
Sky survey Explorer: A sky survey is a systematic search that photographs large areas of the sky repeatedly to find moving or changing objects.
Slag Beginner: Slag is the glassy, often bubbly waste left behind when metal is made from ore, and it is the most common rock mistaken for a meteorite.
Slice Explorer: A thin flat piece cut from inside a meteorite, with sawn faces on both sides.
Solar nebula Explorer: The cloud and disc of gas and dust from which the Sun, planets, asteroids and comets formed about 4.6 billion years ago.
Solar wind gases Expert: Solar wind gases are atoms from the Sun implanted into the surfaces of grains exposed on asteroids, the Moon and other airless bodies.
Sonic boom Explorer: A sonic boom is the thunder-like bang made by a meteoroid moving faster than sound through the air.
South Pole–Aitken basin Enthusiast: The South Pole–Aitken basin is a giant, ancient impact basin on the Moon's far side, about 2,500 kilometres across.
Southern Delta Aquariids Explorer: The Southern Delta Aquariids are a summer meteor shower peaking in late July, best seen from the southern hemisphere.
Space probe Beginner: A space probe is a robotic spacecraft sent to explore other worlds, with no people on board.
Space weathering Expert: The slow alteration of airless surfaces by solar wind, cosmic rays and micrometeorite impacts, which darkens and reddens their spectra.
Spallation Expert: Spallation is the splitting off of fragments, either of rock near an impact or of atomic nuclei struck by cosmic rays.
Specimen label Explorer: A specimen label records a meteorite's name, type, mass and history, and it should always stay with the specimen.
Spinel Expert: Spinel is a magnesium-aluminium oxide that forms tiny hard crystals in CAIs and some impact rocks.
Sporadic meteor Explorer: A meteor that does not belong to any known shower, arriving at random from any direction.
Stable isotope Explorer: A stable isotope is a form of an element whose nucleus does not decay over time.
Stardust mission Enthusiast: Stardust was a NASA mission that collected dust from comet Wild 2 and returned it to Earth in 2006.
Stishovite Expert: Stishovite is an extremely dense form of silica that forms at very high shock pressures and is a strong indicator of meteorite impact.
Stony meteorite Beginner: A stony meteorite is one made mostly of rocky minerals, with little or no metal.
Stony-iron meteorite Beginner: A stony-iron meteorite is made of roughly equal amounts of metal and rocky minerals.
Streak test Beginner: The streak test means rubbing a rock on the back of a ceramic tile to see the colour of its powder.
Strewn field Explorer: A strewn field is the area of ground over which the pieces of a single meteorite fall are scattered.
Strewn field map Explorer: A strewn field map shows where the pieces of a meteorite fall were found, often in an ellipse with the largest at one end.
Suevite Expert: A polymict impact breccia containing fragments of glass or melt, alongside shocked rock and mineral clasts, in a fine-grained matrix.
Sulfide Explorer: A sulfide is a mineral made of a metal combined with sulfur, such as troilite in meteorites.
Sungrazer Expert: A sungrazer is a comet that passes extremely close to the Sun, often skimming through its outer atmosphere.
Superbolide Enthusiast: A superbolide is an extraordinarily bright bolide, usually defined as reaching magnitude −17 or brighter.
Supernova Explorer: A supernova is the explosion of a star, which creates new elements and scatters them into space.
Swathing kamacite Expert: Swathing kamacite is a band of kamacite that surrounds inclusions such as schreibersite or troilite in iron meteorites.

T

Taenite Enthusiast: The nickel-rich form of iron-nickel metal in meteorites, often seen as thin bright ribbons in etched irons.
Taurids Explorer: The Taurids are long-lasting autumn meteor showers known for slow, bright fireballs, linked to Comet Encke.
Tektite Explorer: A piece of natural glass made when a large impact melted rocks on Earth and threw the molten droplets far away.
Terminal velocity Explorer: Terminal velocity is the steady top speed an object reaches when air resistance balances its weight as it falls.
Terrestrial age Enthusiast: The length of time a meteorite has been on Earth since it fell.
Terrestrial fractionation line Expert: The terrestrial fractionation line is the line on an oxygen isotope graph along which all Earth and Moon rocks plot.
Terrestrial weathering Explorer: Terrestrial weathering is the slow breakdown of a meteorite by air, water and temperature changes after it lands on Earth.
Tetrataenite Expert: An ordered iron-nickel alloy, close to half iron and half nickel, that forms only in very slowly cooled metal.
Thermal metamorphism Enthusiast: Thermal metamorphism is the slow heating of rock inside an asteroid, below its melting point, which recrystallises minerals and blurs original textures.
Thermoluminescence Expert: Thermoluminescence is light given off by a mineral when heated, used to measure petrologic subtype and terrestrial age.
Thin section Enthusiast: A thin section is a slice of rock ground so thin, about 0.03 millimetres, that light can shine through it under a microscope.
Thumbprints Beginner: Thumbprints is a common name for regmaglypts, the shallow dents on a meteorite's surface that look as if pressed by thumbs.
Tianwen-2 Expert: Tianwen-2 is a Chinese mission launched in 2025 to collect samples from the small near-Earth asteroid Kamoʻoalewa.
Tissintite Expert: Tissintite is a high-pressure calcium-aluminium silicate first discovered in the Martian meteorite Tissint.
Tochilinite Expert: Tochilinite is an unusual layered mineral of iron sulfide and magnesium hydroxide common in CM chondrites.
Transient crater Expert: The short-lived cavity excavated during an impact before collapse and modification produce the final crater.
Trapped gases Expert: Trapped gases are noble gases incorporated into a meteorite when it formed or during later events, rather than made inside it.
Treasure trove Enthusiast: Treasure trove is an old legal idea about valuable finds; in most places it does not cover meteorites.
Tridymite Expert: Tridymite is a high-temperature, low-pressure form of silica common in eucrites and mesosiderites.
Troilite Enthusiast: An iron sulfide mineral, FeS, common in meteorites and often seen as bronze-coloured nodules in irons.
Troilite nodule Enthusiast: A troilite nodule is a rounded or elongated lump of iron sulfide in an iron meteorite.
Trojan asteroid Enthusiast: A Trojan asteroid shares a planet's orbit, sitting about 60 degrees ahead of or behind it.
Twinning Expert: Twinning is when two or more parts of a crystal grow or deform in mirror-image orientations.
Type I and type II chondrules Expert: Type I chondrules are poor in iron oxide and often contain metal; type II chondrules are rich in iron oxide.
Type specimen Enthusiast: A type specimen is the officially archived portion of a meteorite, kept in a research collection as the reference sample for its classification.

U

Undulatory extinction Expert: Undulatory extinction is a wavy, sweeping pattern of darkness across a crystal under crossed polars, caused by mild shock.
Unequilibrated chondrite Enthusiast: An unequilibrated chondrite is one heated so little on its parent body that its minerals still vary in composition from grain to grain.
Ungrouped meteorite Enthusiast: A meteorite that does not fit into any recognised group, often marked with the abbreviation "ung".
Uranium–lead dating Enthusiast: Uranium–lead dating uses the decay of uranium-238 and uranium-235 into lead to measure ages of billions of years.
Ureilite Enthusiast: A carbon-rich achondrite made mostly of olivine and pyroxene, with graphite and tiny diamonds squeezed between the grains.
Ursids Explorer: The Ursids are a small meteor shower around the winter solstice, radiating from the Little Bear.

V

V-type asteroid Enthusiast: A V-type asteroid has a spectrum like the basaltic crust of Vesta and is linked to the HED meteorites.
Vega missions Expert: Vega 1 and 2 were Soviet spacecraft that visited Venus and then flew past Halley's Comet in March 1986.
Venus Beginner: Venus is the second planet from the Sun, almost Earth's size but with a crushing, scorching atmosphere.
Vera C. Rubin Observatory Explorer: The Vera C. Rubin Observatory in Chile is a large survey telescope expected to discover millions of new asteroids.
Vesicles Enthusiast: Vesicles are small holes in a rock left behind by gas bubbles trapped as molten material solidified.
Vesta Explorer: The second-largest object in the asteroid belt and the likely home of the howardite, eucrite and diogenite meteorites.
Volatile element Expert: A volatile element condenses only at low temperatures and is easily lost when rock is heated, such as sodium, zinc, lead or water.

W

Wadsleyite Expert: Wadsleyite is a high-pressure form of olivine found in shock veins in meteorites and deep in Earth's mantle.
Weather radar Expert: Weather radar can detect falling meteorites in dark flight, helping searchers find where they landed.
Weathering grade Enthusiast: The weathering grade is a code, usually W0 to W6, that records how much a meteorite has rusted and decayed since landing on Earth.
Widmanstätten pattern Explorer: The criss-cross pattern of metal bands that appears when many iron meteorites are cut, polished and etched.
Window Explorer: A window is a small ground and polished patch on the outside of a rock, made to show what the inside looks like.
Winonaite Expert: Winonaites are primitive achondrites closely related to the silicate inclusions found in IAB iron meteorites.
Witnessed fall Beginner: A witnessed fall is a meteorite whose arrival was seen or heard by people.

X

Xenolith Expert: A xenolith is a fragment of foreign rock enclosed in a different meteorite.

Y

Yarkovsky effect Expert: A tiny thrust on a spinning asteroid caused by it giving off absorbed sunlight as heat in a slightly lopsided direction.
YORP effect Expert: The YORP effect is a slow change in an asteroid's spin caused by uneven heating and cooling by sunlight.

Z

Zenithal hourly rate (ZHR) Explorer: The number of meteors one observer would see in an hour under perfect conditions, with the radiant directly overhead.
Zodiacal light Enthusiast: Zodiacal light is a faint glow of sunlight reflected by dust in the plane of the Solar System.
Zoning Expert: Zoning is a gradual or stepwise change in a crystal's chemistry from its core to its edge.