How do scientists officially classify a new meteorite?
A qualified scientist studies a slice under the microscope, analyses its mineral chemistry and sometimes its isotopes, then submits the results to the Meteoritical Society's Nomenclature Committee. Once approved, the meteorite gets an official name and a classification published in the Meteoritical Bulletin.
Turning a promising stone into an officially recognised meteorite follows a well-trodden path. It begins in the laboratory. A researcher at a university, museum or research institute cuts off a small piece and prepares a thin section, a slice of rock ground so thin, about 30 micrometres, that light shines through it. Under a polarising microscope, the scientist identifies the minerals, looks for features such as chondrules, and estimates how much the rock was heated, shocked and weathered.
Next comes chemistry. An electron microprobe, an instrument that fires a fine beam of electrons at individual mineral grains, measures their exact composition. For ordinary chondrites, the amount of iron in minerals such as olivine and pyroxene reveals whether a stone belongs to the H, L or LL group. Unusual meteorites may also need oxygen isotope measurements, which act like a fingerprint for the parent body, or other specialised tests.
The scientist then writes up the results and submits them to the Nomenclature Committee of the Meteoritical Society, the international body that approves meteorite names. A key requirement is the type specimen: a reference sample, usually at least 20 grams or 20 per cent of the meteorite, whichever is smaller, must be deposited in an approved institutional collection so future researchers can study it.
If the committee is satisfied, it approves a name, normally taken from the place where the meteorite fell or was found, and records the classification, such as H5 or eucrite. The entry appears in the Meteoritical Bulletin and its online database. The process can take months, and laboratories may charge for their work. Only then can the stone properly be called a named meteorite.