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#Solar System formation

What chondrites reveal about how the Sun and planets formed 4.6 billion years ago.

Chondrites are the least changed rocks in the Solar System. Their tiny round chondrules and white calcium-aluminium-rich inclusions (CAIs) formed in the disc of gas and dust around the young Sun, before any planets existed.

CAIs are the oldest solids known. They have been dated to about 4,567 million years ago, and that date is used as the age of the Solar System itself.

Because the bodies that chondrites come from never melted, they still hold this first material almost as it was, including microscopic dust grains that are older than the Sun and were made in other stars.

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Lessons (5)

Carbonaceous chondritesCarbonaceous chondrites are rare, often dark and crumbly, and scientifically priceless.
Chondrites: the oldest rocksChondrites are the most common meteorites of all, and some of the most important rocks in science.
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
Oxygen isotopes: the fingerprint of originOxygen makes up nearly half of most rocks by mass, and its three stable isotopes carry a signature that distinguishes parent bodies.
Petrologic types: from wet to hotThe number after a chondrite's group letter, as in H5 or CM2, is its petrologic type. It tells you what happened to the rock inside its

Courses (3)

Extinct radionuclides and the first few million yearsSome radioactive isotopes present when the Solar System formed have long since decayed away.
Chondrites and the birth of the Solar SystemChondrites are the least changed rocks we have. Their components formed in the disc around the young Sun and date the start of the Solar Sys
How the Solar System formedThe Sun and planets formed from a cloud of gas and dust about 4.6 billion years ago.

Famous meteorites (2)

AllendeThe meteorite that fell on a Mexican village months before Apollo 11 – and turned out to hold the oldest solids in the Solar System.
MuonionalustaAn iron meteorite from Arctic Sweden that fell long before the last ice age – and was carried by glaciers before anyone found it.

Meteorite types (7)

CB chondrites (bencubbinites)More than half metal, with chondrules made in a planet-sized collision. CB chondrites, named after Bencubbin in Australia, are more than 50%
CH chondrites'High metal' carbonaceous chondrites with tiny chondrules. CH chondrites are rich in iron-nickel metal, about 20% of the rock by vol
ChondritesPrimitive stones that never melted, made of the first solids of the Solar System. The most common meteorites of all.
CM chondritesWater-rich carbonaceous chondrites full of organic molecules, Murchison and Winchcombe among them.
CO chondritesSmall-chondrule carbonaceous chondrites, close relatives of the CMs. CO chondrites, named after Ornans in France, have very small chondrules
CR chondritesMetal-bearing carbonaceous chondrites with some of the most pristine organic matter known.
CV chondritesLarge chondrules and big white inclusions, the oldest solids in the Solar System. Allende is the classic.

Space missions (2)

GenesisA sample of the Sun itself, which survived a crash landing and rewrote the Solar System's oxygen story.
StardustThe first sample from a comet, and the surprise that it contained rock formed close to the Sun.

Meteorite minerals (22)

AnorthiteCalcium-rich plagioclase, the mineral of the Moon's first crust and of the oldest solids in chondrites.
BrearleyiteA chlorine-bearing calcium aluminate formed when fluids altered an ancient inclusion.
CorundumAluminium oxide, the mineral of ruby and sapphire, found as tiny grains in chondrites, some made in other stars.
DavisiteA scandium-rich pyroxene from an ultra-refractory inclusion in Allende. Davisite is a pyroxene related to diopside in which scandium and alu
DiamondCarbon in its hardest form, found as shock-made crystals in ureilites and as nanodiamonds that may be stardust.
DiopsideA calcium–magnesium pyroxene found in the oldest solids of the Solar System and in many chondrules.
DmitryivanoviteA dense form of calcium aluminate found in the oldest inclusions of carbonaceous chondrites.
GrossiteA calcium aluminium oxide found in rare, extremely refractory inclusions in CH and CR chondrites.
GrossmaniteA pyroxene containing titanium in an unusual state, found in the oldest inclusions in Allende.
HexamolybdenumA tiny alloy of molybdenum and platinum-group metals from the oldest inclusions in Allende.
Hibonite-(Fe)An iron-rich hibonite that formed when an ancient inclusion in Allende was altered.
HiboniteA calcium aluminium oxide, among the very first minerals to condense in the Solar System.
HutcheoniteA titanium-bearing garnet that grew when a CAI in Allende was altered on its parent asteroid.
KrotiteA calcium aluminium oxide found in an unusual refractory inclusion, until then known only from cement.
KushiroiteAn aluminium-rich pyroxene, long known only from laboratory experiments, found in refractory inclusions.
MeliliteA calcium aluminium silicate series, gehlenite to åkermanite, that makes up much of the white inclusions in Allende.
MoissaniteSilicon carbide; its microscopic grains in chondrites are stardust older than the Sun. Moissanite is silicon carbide, almost as hard as diam
NephelineA sodium aluminium silicate that replaces melilite and anorthite in CAIs that were later altered.
PerovskiteA calcium titanium oxide found in the oldest inclusions in chondrites and giving its name to a family of structures.
RhöniteA titanium-bearing chain silicate found in some CAIs and in the oldest basalts from asteroids.
SodaliteA chlorine-bearing sodium aluminium silicate formed by alteration in the CAIs of CV chondrites.
SpinelA hard magnesium aluminium oxide that is one of the first minerals to form around the young Sun. Spinel is an oxide of magnesium and alumini

Questions and answers (15)

Can meteorites tell us how the Sun was born?Yes. Isotopes in meteorites suggest the Sun formed in a cluster of stars, possibly near massive stars that added short-lived radioactive ele
Do meteorites contain stardust older than the Sun?Yes. Primitive meteorites contain tiny presolar grains that formed around other stars before the Sun existed.
How can I teach the solar nebula with a demonstration?Show how spinning causes flattening, using a spinning pizza dough video or a rotating bowl, then model dust clumping into planetesimals with
How do scientists date a meteorite?Scientists measure the products of natural radioactive decay in a meteorite's minerals, using several 'clocks' such as uranium-l
How long did it take to form the planets?Asteroid-sized bodies formed within about the first few million years, Mars largely within about 10 million years, and Earth over roughly 30
How old are meteorites?Most meteorites formed about 4.56 billion years ago, at the birth of the Solar System, making them older than any rock on Earth.
What are short-lived radioactive isotopes and why do they matter?They are radioactive isotopes with half-lives of millions of years or less that existed in the early Solar System.
What can meteorites tell us about the early Solar System?Meteorites act as a time capsule, recording when the first solids formed, how quickly asteroids and planets grew and melted, which stars con
What is a calcium-aluminium-rich inclusion (CAI)?A CAI is a pale inclusion in some chondrites made of high-temperature minerals. CAIs are the oldest solids formed in the Solar System, about
What is a chondrite?A chondrite is a stony meteorite that was never melted after it formed, so it preserves the original mixture of dust and grains from the ear
What is a chondrule?A chondrule is a small, rounded grain, usually less than a few millimetres across, that formed as a molten droplet floating in space in the
What is a CV chondrite?A CV chondrite is a carbonaceous chondrite with large chondrules and abundant CAIs, such as Allende, the source of many key discoveries abou
What is the Allende meteorite?Allende is a large carbonaceous chondrite that fell in Mexico on 8 February 1969, providing tonnes of material rich in CAIs, the oldest soli
What is the oldest thing in a meteorite?The oldest things are tiny grains of stardust that formed around other stars before the Sun existed.
Why do chondrites contain both hot and cold ingredients?Chondrites mix high-temperature chondrules and CAIs with low-temperature dust and organics, showing that materials from different places in

Micrometeorites (2)

What micrometeorites reveal about the early Solar SystemMicrometeorites carry material from many more comets and asteroids than the meteorites in our museums, including fragile, carbon-rich bodies
Catching space dust in the stratosphereThe smallest space dust can be caught before it ever touches the ground. Since the 1970s, high-flying aircraft have collected interplanetary

People (1)

Ernst ZinnerThe physicist who measured single grains of stardust inside meteorites, showing which kinds of stars made them. Ernst K.