This article is the final piece to our original question, “What is the difference between a Meteorite and a Tektite?”  This second piece focuses on the specifics of meteorites. Click the link to learn about tektites.

According to National Geographic, meteorites are space rocks that fall to Earth’s surface. Meteorites are the last stage in the existence of these type of space rocks.

Before they were meteorites, the rocks were meteors. Before they were meteors, they were meteoroids. Meteoroids are lumps of rock or metal that orbit the sun. Meteoroids become meteors when they crash into Earth’s atmosphere and the gases surrounding them briefly light up as “shooting stars.”

While most meteors burn up and disintegrate in the atmosphere, many of these space rocks reach Earth’s surface in the form of meteorites. Dust-sized particles called micrometeorites make up 99 percent of the approximately 50 tons of space debris that falls on the Earth’s surface every day. Some meteorites, however, are as large as boulders. The largest meteorite found on Earth is the Hoba meteorite discovered in Namibia in 1920. The Hoba meteorite weighs roughly 54,000 kilograms (119,000 pounds). The Hoba meteorite is so big, and so heavy, it has never been moved from where it was found!

Most meteorites look very much like rocks found on Earth, except meteorites usually have a dark, burned exterior. This exterior is formed as friction from the atmosphere melts the meteorite as it crashes toward Earth. Known as thermal ablation, this process can also give meteorites a roughened, smooth, or thumbprint surface. Thermal ablation creates these different textures due to different chemicals present in the meteorite.

Meteorites crash through the atmospheres of all planets and moons in our solar system. Some planets and moons don’t have enough atmosphere to break apart meteors, resulting in large meteorites. These larger meteorites create deep, round impact craters that can be found all over our Moon, Mercury, and Mars.

In 2005, the first meteorite found on another planet was discovered by Opportunity, one of NASA’s Mars rover spacecraft. In 2014, Opportunity’s sister spacecraft, Curiosity, discovered a meteorite that was 2 meters (7 feet) wide, making it the largest yet discovered on Mars.

Types of Meteorites

More than 60,000 meteorites have been found on Earth. Scientists have divided these meteorites into three main types: stony, iron, and stony-iron. Each of these types has many sub-groups.

Stony Meteorites

Stony meteorites are made up of minerals that contain silicates—material made of silicon and oxygen. They also contain some metal—nickel and iron. There are two major types of stony meteorites: chondrites and achondrites.

Chondrites themselves are classified into two major groups: ordinary and carbonaceous. Ordinary chondrites are the most common type of stony meteorite, accounting for 86 percent of all meteorites that have fallen to Earth. They are named for the hardened droplets of lava, called chondrules, embedded in them. Chondrites formed from the dust and small particles that came together to form asteroids in the early solar system, more than 4.5 billion years ago. Because they were formed at the same time as the solar system, chondrites are integral to the study of the solar system’s origin, age, and composition.

Ordinary chondrites can be classified into three main groups. The groups indicate the meteorite’s quantity of iron.

The H chondrite group has a high amount of iron.

The L chondrite group has a low amount of iron.

The LL group has a low amount of iron and a low amount of metal in general.

Carbonaceous chondrites are much more rare than ordinary chondrites. Astronomers think carbonaceous chondrites formed far away from the sun as the early solar system developed. As their name implies, carbonaceous chondrites contain the element carbon, usually in the form of organic compounds such as amino acids. Carbonaceous chondrites also often contain water or material that was shaped by the presence of water. Like ordinary chondrites, carbonaceous chondrites can be more minutely classified based on their mineral composition.

All groups of carbonaceous chondrites are marked with a two- or three-letter code starting with C. Carbonaceous chondrites are often named after the first specimen of that type recovered. The CI group, for instance, is named after the Ivuna meteorite, which crashed into Tanzania in 1938. CI meteorites have a high amount of carbon, as well as clays. Carbonaceous chondrites can also be named after the place where the first specimen of the type was found. The CV group is named after a meteorite that crashed near the city of Vigarano, Italy, in 1910. The most famous CV meteorite is probably the Allende meteorite, which fell to Earth near Pueblo de Allende, Chihuahua, Mexico, in 1969. The Allende meteorite has thousands of tiny chondrules made of the mineral olivine. The Allende meteorite also has grains of a special kind of carbon—diamonds. These diamonds are actually older than the solar system, and astronomers think they were produced as blast material from a nearby, ancient supernova.

Achondrites do not contain the lava droplets (chondrules) present in chondrites. They are very rare, making up about 3 percent of all known meteorites. Most achondrites form from the brittle outer layers of asteroids, which are similar to Earth’s crust. There are many classifications of achondrites. The “primitive achondrite” group, for instance, has a very similar mineral composition to chondrites. Lunar meteorites are achondrites that crashed to Earth from the Moon, while Martian achondrites crashed to Earth from our neighbor planet, Mars.

Very few meteorites, only about 0.2 percent, come from Mars and the Moon. These achondrites are the results of Mars and the Moon’s own meteorite impacts. Large meteorites hit the surface of Mars and the Moon, blasting off bits of rock. These rock bits rarely make their way to our atmosphere as meteors and even more rarely hit the Earth’s surface.

Iron Meteorites

Iron meteorites are mostly made of iron and nickel. They come from the cores of asteroids and account for about 5 percent of meteorites on Earth. Iron meteorites are the most massive meteorites ever discovered. Their heavy mineral composition (iron and nickel) often allows them to survive the harsh plummet through Earth’s atmosphere without breaking into smaller pieces. The largest meteorite ever found, Namibia’s Hoba meteorite, is an iron meteorite.

Stony-Iron Meteorites

Stony-iron meteorites have nearly equal amounts of silicate minerals (chemicals that contain the elements silicon and oxygen) and metals (iron and nickel). One group of stony-iron meteorites, the pallasites, contains yellow-green olivine crystals encased in shiny metal. Astronomers think many pallasites are relics of an asteroid’s core-mantle boundary. Their chemical composition is similar to many iron meteorites, leading astronomers to think maybe they came from different parts of the same asteroid that broke up when it crashed into Earth’s atmosphere.

 Meteorite Impact Craters

Meteorites crash through the Earth’s atmosphere with tremendous force. The largest meteorites leave enormous holes in the ground called impact craters. The best-preserved impact crater in the world is the Barringer Meteorite Crater, near Winslow, Arizona. There, more than 50,000 years ago, a meteorite weighing about 270,000 metric tons (300,000 tons) slammed into the Earth with the force of 2.5 million tons of TNT. The impact blasted a hole 1 kilometer (.6 miles) wide and about 230 meters (750 feet) deep. The fragments left of the space rock show that it was an iron meteorite.

More than a hundred impact craters have been identified on Earth. Perhaps the most famous is the Chicxulub Crater, in Yucatan, Mexico. The Chicxulub Crater can be identified on land, beneath dozens of meters of sediment, although about half of the feature is submerged in the Gulf of Mexico. It is one of the larges impact craters ever discovered on Earth. Despite its size, the Chicxulub Craber is famous for another reason. Many scientists think the large meteorite that created the Chicxulub Crater—measuring roughly 10 kilometers (6 miles) wide—triggered the extinction of the dinosaurs and other animal and plant life 65 million years ago.

Fossil meteorites

“Fossil” meteorites are sometimes discovered by geologists. They represent the highly weathered remains of meteorites that fell to Earth in the remote past and were preserved in sedimentary deposits sufficiently well that they can be recognized through mineralogical and geochemical studies. The Thorsberg limestone quarry in Sweden has produced an anomalously large number – exceeding one hundred – fossil meteorites from the Ordovician, nearly all of which are highly weathered L-chondrites that still resemble the original meteorite under a petrographic microscope, but which have had their original material almost entirely replaced by terrestrial secondary mineralization. The extraterrestrial provenance was demonstrated in part through isotopic analysis of relict spinel grains, a mineral that is common in meteorites, is insoluble in water, and is able to persist chemically unchanged in the terrestrial weathering environment. Scientists believe that these meteorites, which have all also been found in Russia and China, all originated from the same source, a collision that occurred somewhere between Jupiter and Mars.  One of these fossil meteorites, dubbed Österplana 065, appears to represent a distinct type of meteorite that is “extinct” in the sense that it is no longer falling to Earth, the parent body having already been completely depleted from the reservoir of near-Earth objects.

Terrestrial

Allende – largest known carbonaceous chondrite (Chihuahua, Mexico, 1969).

Allan Hills A81005 – First meteorite determined to be of lunar origin.

Allan Hills 84001 – Mars meteorite that was claimed to prove the existence of life on Mars.

The Bacubirito Meteorite (Meteorito de Bacubirito) – A meteorite estimated to weigh 20–30 short tons (18–27 t).

Campo del Cielo – a group of iron meteorites associated with a crater field (of the same name) of at least 26 craters in West Chaco Province, Argentina. The total weight of meteorites recovered exceeds 100 tonnes.

Canyon Diablo – Associated with Meteor Crater in Arizona.

Cape York – One of the largest meteorites in the world. A 34-ton fragment called “Ahnighito”, is exhibited at the American Museum of Natural History; the largest meteorite on exhibit in any museum.

Gibeon – A large Iron meteorite in Namibia, created the largest known strewn field.

Hoba – The largest known intact meteorite.

Kaidun – An unusual carbonaceous chondrite.

Mbozi meteorite – A 16-metric-ton ungrouped iron meteorite in Tanzania.

Murchison – A carbonaceous chondrite found to contain nucleobases – the building block of life.

Nōgata – The oldest meteorite whose fall can be dated precisely (to 19 May 861, at Nōgata)

Orgueil – A famous meteorite due to its especially primitive nature and high presolar grain content.

Sikhote-Alin – Massive iron meteorite impact event that occurred on 12 February 1947.

Tucson Ring – Ring shaped meteorite, used by a blacksmith as an anvil, in Tucson AZ. Currently at the Smithsonian.

Willamette – The largest meteorite ever found in the United States.

2007 Carancas impact event – On 15 September 2007, a stony meteorite that may have weighed as much as 4000 kilograms created a crater 13 meters in diameter near the village of Carancas, Peru.

2013 Russian meteor event – a 17-metre diameter, 10 000 ton[96] asteroid hit the atmosphere above Chelyabinsk, Russia at 18 km/s around 09:20 local time (03:20 UTC) 15 February 2013, producing a very bright fireball in the morning sky. A number of small meteorite fragments have since been found nearby.

Extraterrestrial

Bench Crater meteorite (Apollo 12, 1969) and the Hadley Rille meteorite (Apollo 15, 1971) − Fragments of asteroids were found among the samples collected on the Moon.

Block Island meteorite and Heat Shield Rock – Discovered on Mars by Opportunity rover among four other iron meteorites.[100] Two nickel-iron meteorites were identified by the Spirit rover. 

Large impact craters

Acraman crater in South Australia (90 kilometres (56 mi) diameter)

Ames crater in Major County, Oklahoma 16 kilometres (9.9 mi) diameter

Brent crater in northern Ontario (3.8 kilometres (2.4 mi) diameter)

Chesapeake Bay impact crater (90 kilometres (56 mi) diameter)

Chicxulub crater off the coast of Yucatán Peninsula (170 kilometres (110 mi) diameter)

Clearwater Lakes a double crater impact in Québec, Canada (26 and 36 kilometres (16 and 22 mi) in diameter)

Lonar crater in India (1.83 kilometres (1.14 mi) diameter)

Lumparn in Åland, in the Baltic Sea (9 kilometres (5.6 mi) diameter)

Manicouagan Reservoir in Québec, Canada (100 kilometres (62 mi) diameter)

Manson crater in Iowa (38 kilometres (24 mi) crater is buried)

Meteor Crater in Arizona, also known as “Barringer Crater”, the first confirmed terrestrial impact crater. (1.2 kilometres (0.75 mi) diameter)

Mjølnir impact crater in the Barents Sea (40 kilometres (25 mi) diameter)

Nördlinger Ries crater in Bavaria, Germany (25 kilometres (16 mi) diameter)

Popigai impact structure in Russia (100 kilometres (62 mi) diameter)

Siljan Ring in Sweden, largest crater in Europe (52 kilometres (32 mi) diameter)

Sudbury Basin in Ontario, Canada (250 kilometres (160 mi) diameter).

Ungava Bay in Québec, Canada (260 by 320 kilometres (160 by 200 mi))

Vredefort impact structure in South Africa, the largest known impact structure on Earth (300 kilometres (190 mi) diameter from an estimated 10 kilometres (6.2 mi) wide meteorite).

Disintegrating meteoroids

Tunguska event in Siberia 1908 (no crater)

Vitim event in Siberia 2002 (no crater)

Chelyabinsk event in Russia 2013 (no known crater)