The journey to have a suspected space rock officially recognized as a meteorite is a precise process that transforms an interesting find into a scientifically validated and cataloged object. Classification provides the meteorite with an official name, a detailed scientific description, and a permanent record within the international community. This formal validation is granted by the Meteoritical Society’s Nomenclature Committee after rigorous analysis. The process ensures the discovery contributes meaningfully to planetary science and distinguishes the find from countless similar terrestrial rocks.
Initial Assessment of Potential Meteorites
The first step for any finder is to conduct simple, non-destructive tests to determine if the rock is a likely candidate. Most meteorites contain iron and nickel metal, meaning they will be strongly attracted to a powerful magnet, which is the most straightforward preliminary test. Meteorites are also noticeably denser than most common Earth rocks of comparable size.
A fresh meteorite typically exhibits a dark, thin exterior coating called a fusion crust, which forms when the surface melts from intense heat upon entering the Earth’s atmosphere. This crust can be matte or slightly glossy black, and sometimes the surface shows shallow, thumbprint-like indentations known as regmaglypts. Conversely, most Earth rocks mistakenly identified as meteorites often have small holes or bubbles called vesicles, characteristic of volcanic rocks but absent in most meteorites. A simple streak test on an unglazed ceramic surface can help rule out common iron ores like magnetite or hematite, which leave a dark or reddish-brown streak, whereas a stone meteorite typically leaves no streak.
Submitting the Sample for Scientific Review
Once preliminary tests suggest a genuine extraterrestrial origin, the next phase involves formal scientific review, requiring the submission of a sample to an accredited institution. Classification work is typically conducted by a Principal Investigator at a university or museum laboratory approved by the Meteoritical Society. The finder must provide a small, representative submission sample, which should be approximately 20 grams or a minimum of 20% of the total mass, whichever is less.
The laboratory process begins with meticulous sample preparation, including the creation of a petrographic thin section. This is a slice of the meteorite so thin that light can pass through it, allowing scientists to examine its internal structure under a high-powered microscope. Microscopic analysis identifies key features, such as chondrules, which are tiny, spherical mineral grains found in the most common type of stony meteorites called chondrites.
The scientific classification relies heavily on quantitative chemical analysis using an Electron Probe Micro-Analyzer (EPMA), often called a microprobe. This specialized instrument determines the precise mineral composition and chemical ratios of individual mineral grains within the sample. For stony meteorites, scientists measure the iron-to-nickel ratios within minerals like olivine and pyroxene, as these values are distinct for different meteorite groups. This detailed compositional data provides the scientific fingerprint necessary to definitively classify the specimen.
Understanding the Scientific Designation
Upon successful classification, the meteorite receives a permanent, unique designation following a standardized nomenclature system. This designation begins with an acronym identifying the geographic region of the find, such as NWA for Northwest Africa or ALH for Allan Hills in Antarctica. The acronym is then followed by a unique number assigned sequentially as meteorites are classified from that region.
The classification places the new find within one of the three main categories: stony, iron, or stony-iron meteorites.
Stony Meteorites
Stony meteorites, the most common type, are further divided into chondrites, which contain chondrules, and achondrites, which lack them and resemble terrestrial volcanic rocks. Achondrites include rare samples from the Moon and Mars.
Iron and Stony-Iron Meteorites
Iron meteorites consist primarily of iron-nickel metal. Stony-iron meteorites are a mixture of metal and silicate minerals, such as pallasites, which feature olivine crystals embedded in a metal matrix.
This designation is a permanent scientific record that allows researchers globally to understand the material’s origin and characteristics. The precise chemical and petrographic details define the specimen’s unique place in the meteorite family tree.
Registering the Find and Ethical Guidelines
The final step is the submission of all classification data to the Meteoritical Bulletin Database, the official international catalog of all recognized meteorites. The scientist who conducted the analysis is responsible for submitting the classification details, including the find location, date, total mass, and the full scientific description.
A fundamental requirement for official classification is the permanent archiving of a portion of the material, known as the “type specimen,” in a scientific institution. The finder must donate at least 20 grams or 20% of the total known mass, whichever is less, to a recognized repository for long-term study and preservation. This ensures the scientific community has access to a piece of the meteorite for future research. Although the finder retains ownership of the remaining material, classification and registration provide the ethical foundation for any subsequent sale or donation.