Fireballs, camera networks and recovery

Modern camera networks can turn a few seconds of light into a meteorite in a museum within days. This lesson explains how, and how members of the public help.

From fireball to dark flight

A meteoroid enters at 11 to 72 km/s. Compressed air ahead of it becomes intensely hot; the surface melts and is swept away. Most of the mass is lost. Air pressure often breaks the body into fragments. Lower down, at roughly 30 to 10 km, the pieces slow to a few hundred kilometres per hour, stop glowing and fall in dark flight, drifting with the wind. They land at terminal velocity, cool inside, with a thin black fusion crust.

Triangulation

When two or more cameras record the same fireball from different places, its path can be reconstructed in three dimensions, with its speed and deceleration. That gives two results. Projecting the path backwards gives the orbit before it met Earth. Modelling dark flight with wind data gives a predicted strewn field on the ground, typically a few kilometres long, where searchers walk in lines.

The 2021 Winchcombe fall in England was found this way, with help from doorbell cameras, and dedicated networks in Europe, North America and Australia now recover several falls a year. In 2008 the small asteroid 2008 TC3 was even spotted in space about 20 hours before it struck over Sudan, and its fragments, called Almahata Sitta, were later collected from the desert.

How you can help

If you see a fireball, note the time, your location, the direction you were facing, where it started and ended in the sky, its colour, how long it lasted and any sound, then report it to a national meteor or fireball network. Dashcam and doorbell footage is especially valuable.

If you find a fresh meteorite after a fall, do not handle it with bare hands. Pick it up with clean foil or a clean bag, record the exact location with a photo and GPS position, keep it dry, and contact a museum or university. Always have the landowner's permission to search.

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