Howardites
Topic

#Achondrites

Stony meteorites from bodies that melted: crust and mantle rocks from asteroids, the Moon and Mars.

Lessons (7)

  • Achondrites: rocks from melted worldsAchondrites are stony meteorites without chondrules. They come from worlds that melted, and many of them look surprisingly like volcanic roc
  • Classifying a new meteoriteThis final lesson brings the course together, following a new meteorite from arrival at the laboratory to an approved name in the Meteoritic
  • Early Solar System chronologyMeteorites let us build a timeline of the first few million years of the Solar System with a precision that seems almost impossible. Here is
  • Identifying a possible meteoriteMost suspected meteorites turn out to be Earth rocks. This lesson sets out a careful, non-destructive approach, and explains what only a lab
  • Primitive achondrites and ureilitesBetween chondrites and fully melted achondrites lie rocks caught in the act of melting. They reveal how differentiation begins.
  • The classification frameworkMeteorite classification is a hierarchy built on petrology, bulk chemistry and isotopes.
  • The NC–CC isotopic dichotomyNucleosynthetic isotope anomalies split meteorites into two great families that formed in separate regions of the disc.

Courses (2)

  • Igneous petrology of meteoritesMelting and crystallisation on asteroids, the Moon and Mars produced igneous rocks that geologists read with the same tools used on Earth.
  • How meteorites are classifiedTens of thousands of meteorites are sorted into a system of classes and groups. This lesson explains the main branches and what the labels o

Books (1)

Famous meteorites (6)

  • Almahata SittaThe first asteroid spotted in space before it hit the Earth – and the meteorites later collected from the Sudanese desert.
  • JuvinasA single basaltic stone that fell in southern France in 1821 and helped show that some asteroids once had volcanoes.
  • MillbillillieA eucrite that fell in the Western Australian outback in 1960, famous for its glossy black fusion crust.
  • Norton CountyA shower of pale, almost iron-free stones over the Kansas–Nebraska border in 1948, including the largest aubrite ever found.
  • StannernA shower of basaltic stones that fell on Moravia in 1808 and gave its name to a distinctive kind of lava from Vesta.
  • TatahouineA meteorite that shattered into green crystals in the Tunisian desert in 1931 – a fragment from deep inside the asteroid Vesta.

Meteorite types (28)

  • AcapulcoitesFine-grained rocks that only just began to melt. Named after Acapulco in Mexico, which fell in 1976, acapulcoites are fine-grained rocks of
  • AchondritesIgneous stones from bodies that melted: asteroids, the Moon and Mars. An achondrite is a stony meteorite without chondrules.
  • AngritesThe oldest volcanic rocks known, from a vanished early planetesimal. Named after Angra dos Reis in Brazil, which fell in 1869, angrites are
  • Asteroidal achondritesFully melted, differentiated rocks from the crusts and mantles of asteroids, Vesta above all.
  • AubritesPale, almost iron-free rocks made of enstatite, from an extremely oxygen-poor world.
  • BrachinitesOlivine-rich rocks from an asteroid whose melt drained away. Named after Brachina in South Australia, brachinites are made mostly of iron-ri
  • ChassignitesOlivine-rich Martian rocks; the first known fell in France in 1815. Chassignites are dunites, rocks made almost entirely of olivine, that fo
  • DiogenitesPyroxene-rich rocks from deep inside Vesta. Diogenites are coarse-grained rocks made mostly of orthopyroxene, sometimes with olivine.
  • EL chondritesLow-iron enstatite chondrites. EL chondrites have less metal than EH chondrites and contain alabandite, a manganese sulphide, instead of nin
  • Enstatite chondritesChondrites formed with almost no oxygen to spare, full of rare minerals unknown on Earth's surface.
  • EucritesVolcanic basalt from the crust of Vesta. Eucrites are basalts and gabbros from Vesta's crust, made mainly of pigeonite (a calcium-poor p
  • HED meteorites: pieces of VestaThe howardites, eucrites and diogenites: crust and mantle rocks from the giant asteroid 4 Vesta. The meteorites this site is named after.
  • HowarditesBroken rubble from the surface of asteroid Vesta, mixing crust and mantle rocks. Howardites are regolith breccias: rocks made from the broke
  • LodranitesCoarse-grained leftovers after melt drained away. Named after Lodran in Pakistan, which fell in 1868, lodranites are coarser-grained than ac
  • Lunar basalts and gabbrosDark volcanic rock from the lunar maria, the Moon's great lava plains. Lunar basalts are pieces of the dark lava plains, the maria, that
  • Feldspathic lunar meteoritesPale breccias from the ancient lunar highlands, the most common kind of Moon rock to reach Earth.
  • Lunar meteoritesRocks from the Moon, found mainly in deserts and Antarctica. Lunar meteorites are pieces of the Moon blasted off by impacts.
  • Mingled lunar brecciasBreccias that mix highland and mare rock, from the borders between the two. Mingled breccias contain both pale highland material and dark ma
  • Martian meteoritesRocks from Mars, recognised by gas from the Martian atmosphere trapped inside them.
  • ALH 84001 and other Martian rocksThe ancient Martian rock once claimed to hold fossils, and 'Black Beauty'. Allan Hills 84001, found in Antarctica in December 1984,
  • NakhlitesAugite-rich volcanic rocks from Mars, about 1.3 billion years old. Nakhlites, named after Nakhla in Egypt (fell 1911), are made mainly of au
  • Planetary achondritesRocks knocked off the Moon and Mars by impacts. A few achondrites come not from asteroids but from much larger worlds.
  • Primitive achondritesRocks that began to melt but were never fully processed: halfway between chondrites and igneous rocks.
  • ShergottitesThe most common Martian meteorites: young basaltic and olivine-rich rocks. Shergottites, named after Shergotty in India (fell 1865), make up
  • Stony meteoritesMeteorites made mostly of silicate minerals. They are by far the most common kind seen to fall.
  • Ungrouped achondritesMelted rocks that match no known group: each may be the only sample of its own world. Some achondrites fit none of the named groups.
  • UreilitesCarbon-rich rocks with diamonds, from an asteroid shattered by a giant impact. One was tracked in space before it hit Earth.
  • WinonaitesPrimitive achondrites related to the silicate inclusions in IAB irons. Named after the Winona meteorite, found buried in a Sinagua ruin in A

Meteorite minerals (10)

  • CaswellsilveriteA sodium chromium sulphide from enstatite meteorites. Caswellsilverite is a layered sulphide of sodium and chromium.
  • DiamondCarbon in its hardest form, found as shock-made crystals in ureilites and as nanodiamonds that may be stardust.
  • EnstatiteThe magnesium pyroxene that dominates enstatite chondrites and aubrites, and many chondrules.
  • GraphiteSoft, layered carbon, found as nodules in iron meteorites, in ureilites and in primitive chondrites.
  • KirschsteiniteA calcium–iron olivine-group mineral typical of angrites, the oldest basalts in the Solar System.
  • OldhamiteCalcium sulphide, which exists only where there was almost no oxygen, as in enstatite meteorites. Oldhamite is calcium sulphide.
  • OsborniteTitanium nitride, golden cubes found in enstatite meteorites and in comet dust. Osbornite is a compound of titanium and nitrogen, extremely
  • PerryiteA nickel silicide-phosphide found in the metal of enstatite chondrites and aubrites. Perryite is a compound of nickel and iron with silicon
  • RhöniteA titanium-bearing chain silicate found in some CAIs and in the oldest basalts from asteroids.
  • SuessiteAn iron silicide formed in ureilites, where carbon stripped oxygen from silicates. Suessite is a compound of iron and silicon.

Glossary (17)

Questions and answers (14)

Impact events (1)

  • Asteroid 2024 BX1A predicted fall that brought down one of the rarest kinds of meteorite. On the evening of 20 January 2024 Krisztián Sárneczky, who had foun

Asteroids (2)

  • 2008 TC32008 TC3 was the first asteroid ever found in space before it hit the Earth. Richard Kowalski spotted it on 6 October 2008 with a survey tel
  • ŠteinsŠteins is a small asteroid with an unusual make-up. It belongs to the rare E-type asteroids, which are very bright because their surfaces ar

People (3)

  • Lincoln LaPazThe director of the Institute of Meteoritics in New Mexico, who tracked fireballs from eyewitness reports and recovered the giant Norton Cou
  • Muawia ShaddadThe University of Khartoum astronomer who led students across the Nubian Desert to recover Almahata Sitta in 2008. Muawia H.
  • Richard KowalskiThe Catalina Sky Survey astronomer who discovered 2008 TC3, the first asteroid ever found before it hit the Earth. Richard A.

Museums and collections (2)

Meteorites (the 60 largest of 2,129)