What is a meteorite?

Most “shooting stars”, or meteors, burn up in the earth’s atmosphere never to be seen again. When a piece survives the trip and impacts the surface of the Earth, it is known as a meteorite. Thousands of meteorites have been identified and cataloged, with many winding up in museums or research institutions. Luckily for us, many also wind up in the hands of collectors. Meteorite collecting can be a fascinating hobby – the specimens are interesting for their science, history, and aesthetic value. Like crystals and fossils, meteorites are a great way to bring a part of natural history into your home.

How do we know when a rock is a meteorite?

Hundreds of meteorites fall to the Earth each year, but most go unnoticed. Still, an average of 5 or 6 meteorite falls are witnessed and documented each year. By recovering these rocks and studying them, scientists have determined several differences between Earth rocks and meteorites. Of the 300 or so minerals found in meteorites, there are about 40 that are not normally found on Earth. In addition to these mineral cues, most meteorites display telltale characteristics including a blackened outside (known as fusion crust), attraction to a magnet (due to the presence of iron-nickel inclusions), and small spherical structures within the interior (known as chondrules).

Using this knowledge, “meteorite hunters” have combed the Earth and found thousands of previously unobserved meteorites. Many have also been found purely by accident – for example, by a farmer plowing their field. Before a suspect meteorite is made official, it must pass a series of stringent chemical tests. Only then can it be officially named and accepted as a true meteorite.

What are meteorites made of?

Most rocks that impact the Earth are thought to originate in the asteroid belt, between the planets Mars and Jupiter. When two asteroids collide, rock and metal is strewn into space. With each collision, many tons of material are sent out into space. These fragments may drift for millions of years before eventually impacting the Earth, Moon, or another planet.

Most meteorites are primarily stone, consisting of minerals like olivines and pyroxenes. The most abundant meteorites, known as chondrites, represent the solar system’s most primitive rocks. These specimens contain small spherical inclusions known as chondrules – the solar system’s first solid matter. Other meteorites come from parent bodies that are less primitive, having undergone igneous activity. These meteorites include achondrites, stony-irons, and irons – each originating from a different depth within an asteroid.

On rare occasions, impacts with a larger world are forceful enough to send planetary material out into space. Meteorites have been identified that are believed to be from the planet Mars, the Moon, and possibly even Mercury. In the case of Lunar meteorites, samples have been compared to rocks brought back by the Apollo missions and shown striking similarities. In Martian meteorites, trace elements have been identified that are in the correct proportions for the atmosphere of Mars, as measured by spacecraft like Viking 1 & 2, Pathfinder, and more recently by NASA’s Mars Exploration Rovers, Spirit and Opportunity.

How are meteorites named?

Each meteorite is named after the location where it is found. When a specific city name is not available, it is named after the region (such as NWA for Northwest Africa). Many have been found in desert regions such as the Sahara, where black meteorites stand out against the otherwise featureless terrain.