The difference between asteroids and meteorites
Then a light streaks across the sky and is gone. “Wow, a shooting star,” you think. “A meteor. Wait or is it a meteorite? Or a meteoroid?”. The only difference is were they are in the cycle. A Meteoroid is a rock still in space, and has not hit the atmosphere yet. A Meteor is the same rock falling through. They become meteors—or shooting stars—when they fall through a planet's Several times a year, Earth passes through a trail of debris creating meteor.
Murchison, Australia CM2 Similar to the mantles and crusts of the terrestrial planets. Most meteorites are chondrites. Salaices H4 Primarily iron and nickel. Similar to type M asteroids. Similar to type S asteroids. Iron meteorites consist almost entirely of a mixture of metallic nickel and iron. They are easier to spot on the ground because their highly unoxidized iron content stands out from background rocks.
The outer surface of iron meteorites often melts during their passage through the atmosphere resulting in a dark fusion crust.
Primary fusion crust forms while the meteoroid is incandescent.
How are meteoroids, meteors and meteorite related?
Secondary fusion crust forms on the broken surfaces of fragments which break free from the main mass during incandescent flight. They may also exhibit flow markings and interesting molten metal shapes. The interior of some iron meteorites displays a criss-cross pattern of different iron-nickel minerals.
Iron meteorites may originate in the cores of differentiated parent bodies at least km in diameter. The composition of some main-belt asteroids called M-type asteroids resembles that of iron meteorites.
These M-type asteroids may be the source of iron meteorites. Iron meteorites with weights of 50 to kg are not uncommon. The Hoba meteorite, at 60 tons, is the largest known iron meteorite to have landed without exploding.
It still lies where it was found.
Silicates are minerals containing silicon, oxygen, and one or more metals. Stony meteorites are difficult to find because they look like terrestrial rocks. The best places to find stony meteorites are in deserts or on the ice sheet of Antarctica. The meteorites stand out against the background of ice or sand. Like iron meteorites, stony meteorites often exhibit a dark fusion crust. There are three major subgroups of stony meteorites, Chondrites, Carbonaceous Chondrites, and Achondrites.
Chondrites are the most common type of stony meteorite. Chondrites are composed of small spherical chondrules. Chondrules are millimeter to centimeter sized glassy mineral spheres. Chondrules are composed of silicate material that has melted and then resolidified.
Chondrules formed early in solar system history. They were the most primitive "building blocks" of the solar system. Over time chondrules accreted to form larger and larger objects including asteroids, moons, and planets.
In some chondrites the chondrules are separated by patches of iron metal.
Different types of chondritic meteorites contain different amounts of metal. They have been heated to varying degrees. Chondrites are called primitive because they have changed very little since their initial formation early in the history of the solar system. Their composition resembles that of the Sun except that the lightest gases Hydrogen and Helium are missing from the meteorites.
Enstatite chondrites are metal rich meteorites in which the primary mineral is Enstatite. Enstatite chondrites may be fragments of asteroid 16 Psyche. Some scientists have suggested Mercury as the originating body.
Carbonaceous Chondrites are essentially just pieces of chondrules stuck together. They are very black because of their high carbon content. Some of their mineral grains predate the solar system -- probably fragments blown out from distant stars that became supernovae.
Carbonaceous chondrites also contain water and amino acids. Some types of carbonaceous chondrites may be cometary material. The building blocks of life on Earth may have been seeded by comets and carbonaceous meteorites early in Earth's history. For example, the Murchison meteorite, a fragment of which appears in the table above, was found in This carbonaceous chondrite contains 16 amino acids, 11 of which are rare on Earth.
It may represent the type of cosmic visitor which early in the Earth's history brought the raw materials needed to jump start life. In some stony meteorites called achondrites the chondrules have been partially or completely destroyed by metamorphic processes.
This took substantial time and pressure. Such meteorites must be fragments of the interior of larger bodies on which the weight of the overlying rock created enough pressure to obliterate the chondrules. Some achondrites resemble terrestrial igneous rocks and formed during volcanic eruptions on planets and asteroids. Some asteroids like Vesta heated up enough that their interiors melted and erupted lava onto their surfaces.
The lava hardened into a rock called basalt. Egerton meteorite see table above is a type of achondrite known as an aubrite. Fragments of DAG Mars Rock Some achondrites are composed of rock fragments broken and fused back together during an impact event.
Meteorites believed to originate from the Moon and Mars are achondrites that formed during impact events. The achondrite Dar al Gani see photo of fragments at right is a type known as a Shergottite. It probably originated as a fragment of the planet Mars blasted off the surface during a large impact event.
The difference between asteroids and meteorites
The heaviest known stony meteorite was Jilin which weighed 1. It fell in Jilin, China on March 8, as part of a meteorite shower see below which produced about four tons of meteoric material altogether. Witnesses of Jilin report a spectacular daytime fireball and several explosions. Jilin is classfied as an olivine-bronzite chondrite H5.
Because the Chinese leader Mao Zedung died three days after this fall, many Chinese took Jilin as an omen.
There are two main groups of stony iron meteorites. Asteroids Asteroids are found mainly in the asteroid belt, between Mars and Jupiter. Sometimes their orbits get perturbed or altered and some asteroids end up coming closer to the Sun, and therefore closer to Earth. In addition to the asteroid belthowever, there have been recent discussions among astronomers about the potential existence of large number asteroids in the Kuiper Belt and Oort Cloud.
Asteroids are sometimes referred to as minor planets or planetoids, but in general, they are rocky bodies that do not have an atmosphere. However, a few have their own moons. Our solar system contains millions of asteroids, many of which are thought to be the shattered remnants of planetesimals — bodies within the young Sun's solar nebula that never grew large enough to become planets.
The size of what classifies as an asteroid is not extremely well defined, as an asteroid can range from a few meters wide — like a boulder—to objects that are hundreds of kilometers in diameter. The largest asteroid is asteroid Ceres at about km miles in diameter, and Ceres is so large that it is also categorized as a dwarf planet. Most asteroids are made of rock, but as we explore and learn more about them we know that some are composed of metal, mostly nickel and iron.
According to NASA, a small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Recently, astronomers have discovered some asteroids that mimic comets in that gas and dust are emanating from them, and as we mentioned earlier, there appears to be a large number of bodies with asteroid-like compositions but comet-like orbits. An artists impression of an asteroid belt.
NASA While we know that some asteroids pass very close to Earth's orbit around the Sun, we've been lucky in the history of humanity that we haven't had a large asteroid hit Earth in the past several thousand years.
It wasn't until satellite imagery of Earth became widely available that scientists were able to see evidence of past asteroid impacts. One of the more famous impact craters on Earth is Meteor Crater in Arizona in the US, which was made by an impact about 50, years ago. But there are about known impact around the world — a few are quite large, like Vredefort Crater in South Africa which has an estimated radius of kilometers milesmaking it the world's largest known impact structure on Earth.
Meteors, Meteoroids, and Meteorites
Another notable impact site is off the coast of the Yucatan Peninsula in Mexico, and is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago. These days, asteroid impacts are less of a threat.
NASA estimates that about once a year an automobile-sized asteroid enters Earth's atmosphere, creates an impressive fireball and disintegrates before ever reaching the surface.
Studies of Earth's history indicate that about once every 5, years or so on average an object the size of a football field hits Earth and causes significant damage. Once every few million years on average an object large enough to cause regional or global disaster impacts Earth.
Meteors, Meteoroids and Bolides Space debris smaller than an asteroid are called meteoroids. A meteoroid is a piece of interplanetary matter that is smaller than an asteroid and frequently are only millimeters in size. Most meteoroids that enter the Earth's atmosphere are so small that they vaporize completely and never reach the planet's surface.
When they burn up during their descent, they create a beautiful trail of light known as a meteor, sometimes called a shooting star. Mostly these are harmless, but larger meteors that explode in the atmosphere — sometimes called bolides—can create shockwaves, which can cause problems.
In February a meteor that exploded over Chelyabinsk, Russia shattered windows with its air blast. This meteoroid or bolide was estimated to be 18 meters 59 feet in diameter. Ina rocky meteoroid less than meters in diameter is believed to have entered the atmosphere over the Tunguska region of Siberia in and the resulting shockwave knocked down trees for hundreds of square kilometers.
How often is Earth hit by meteroids? Because of the Chelyabinsk meteor inastronomers have acquired more information about the frequency of larger meteors that hit Earth, and there is now a growing consensus that the Earth gets hit by bigger space rocks more often than we previously thought.
- What’s the Difference Between a Meteoroid, a Meteor, and a Meteorite?
- Meteors, Meteoroids, and Meteorites