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METEORITES FOR SALE
About Meteorites
Meteorites are defined as chunks of space rock of any size that has breached the Earth’s atmosphere and collided with the surface. Space rock is constantly falling from the sky and has the potential to become a meteorite. Although unless the projectile is larger than the size of an American football field then it will disintegrate as it hits the atmosphere and is subjected to different pressures. This break up is why most of the meteors found are smaller than the size of a fist. Although the average meteorite is somewhere between the size of a coin and a baseball, there are some meteorites that kept a portion of their significant mass as they crashed down to earth with two 30+ ton meteorites in Greenland and Argentina, and a 60+ ton chunk lodged in the ground in Namibia.
A 60 ton meteorite is a staggering size considering that only about 5% of the original body makes it through the atmosphere when all is said and done. That equates to the meteoroid responsible for the Hoba meteorite to be at the very least ~1,300 tons in mass.
Many meteorites are rather unassuming and look a lot like any other Earth rock but may be slightly shinier. This shine is the product of the outer surface melting from the extreme heat of atmospheric entry and is referred to as, “fusion crust”. These rocks are often a dark red-brown, are pocked or “porous”, and quite hefty for their size. Meteorites are a lot more rock-like in appearance than the impact glasses that are associated with the meteorite impact, which are often much more colorful.
The overall smoothness of meteorites may be one of their dead giveaways. Granted many other stones may be smoothed by erosion either from sand abrasion, hydrological forces, or wind exposure. However, meteorites have a shiny, glossy look that resulted from superheating upon entry and crashing down. It’s a subtle difference, but it is observable. When all is said and done, most agree that the density of meteorites is the most remarkable and what most use as a physical indicator without intrusive chemical testing.
Where Do Meteorites Come From?
Put simply. Space. They come from space. More specifically 99.8% of the meteorites on Earth originated in the asteroid belt between Mars and Jupiter or from random asteroids and meteoroids floating around out there. However, the remaining 0.2% of the meteorites are consistent with material found on Mars and the moon. The meteorites from the moon and Mars are important to scientist’s understanding of how interstellar collisions happen between the planets and celestial bodies within the Milky Way.
Meteorites aren’t necessarily formed, so much that they are broken off of extraterrestrial bodies from impacts and collisions in space. Often these meteoroids will drift around in space as debris, asteroids, or comets before they enter the earth’s atmosphere, explode, and fall to the surface. One could say that meteorites are formed as a larger rocky mass disintegrates from high pressure and superheating of the rocks as they fall.
Meteorites are found all over the world. That said, some areas seem to experience more impacts than others. Maps that chart the 190 confirmed impacts with Earth show a trend of impact at northern and southern latitudes with little attention to areas nearest the equator. It’s easiest to find meteorites in large, flat, open areas like deserts where they are less difficult to spot. Another important thing to remember is that meteorites aren’t often found after meteor showers. This is simply because the material that makes up the comets responsible for the showers is quite fragile and will be too small to have a chance to enter the atmosphere. It is only significantly large extraterrestrial bodies that produce meteorites of viable entry size.
How Do They Classify Meteorites?
This is a rather complex topic, but here is a brief overview. Depending on who you ask, there are a few different classification schemes. The primary scheme divides meteorites into three types based on their composition: stony, iron, and stony-iron. These classifications are observable by physical differences in the texture and weight of the meteorite , which also gives clues about the age and origin of the meteorite. This is the traditional scheme that is further subdivided by the Rubin Catalog (2000) and its progenitor’s alternate schemes, Krot et al. (2003) and Weisberg et al. (2006). These schemes all operate on the basis of the traditional scheme with numerous ways to alternately subclassify based upon a variety of factors that change as information becomes available.
Meteorite Classifications
Stony meteorites are composed of rocky material and look a lot like porous stone. These bodies make up most of the meteorites we know about. The material that stony meteorites are made of is believed to have once been the crust of the planetary remnants that make up the asteroid belt. Stony meteorites can be further subdivided into two types called chondrites and achondrites. Chondrites are meteorites that contain grainy inclusions called chondrules which were once a part of the solar nebula that dates prior to the creation of, not only the Earth, but our solar system as well. Chondrites provide scientists with data about what the vastness of space was like before the solar system’s existence and contain the oldest material observable on Earth. Achondrites lack chondrules and are thought to be composed of volcanic rock created by the now obliterated planetary volcanoes of the asteroid belt.
Iron type meteorites are primarily composed of iron and other metals—primarily nickel. These metallic meteorites are often the easiest to identify after millions of years post-impact, because they are quite different from the surrounding material, especially when it comes to their mass-to-surface area ratio. They are exceptionally heavy for their size as iron is one of the metals with a high density. Extraterrestrial iron and nickel are believed to be chunks of the cores of the planetary devastation that is now the asteroid belt.
Unsurprisingly, stony-iron types are a mixture of rocky and metallic components. This class of meteorite has a lot of the appearance of the rocky material but the weight of the iron meteorites. These meteorites are a catch-all category that falls outside of the metal meteorites and anything that isn’t either a chondrite or achondrite.
Additionally, institutions generally well-informed on the happenings in space, such as NASA, have begun to classify meteorites as either undifferentiated or differentiated. This separation is demarcated by the process of differentiation which is when the individual components of the meteorite separate and gather by likeness within the molten body as it cools. This is why the iron content of stony-iron meteorites is in the center of the meteorite. Undifferentiated meteorites are composed of either a singular component or are too small to differentiate as they cooled faster than larger chunks during atmospheric entry. As it stands, chondrites are classified as undifferentiated meteorites, and iron, achondrites, and stony-iron types are differentiated meteorites.
Meteorite Classification Chart from Nasa.gov