Pre-atmospheric size
Pre-atmospheric size is the size of a meteoroid before it entered Earth's atmosphere and lost material to ablation and break-up.
A meteorite that reaches the ground is usually a small fraction of the meteoroid that entered the atmosphere. Most of the original material is lost to ablation, as the surface melts and vaporises, and to fragmentation into dust and small pieces. The pre-atmospheric size is the original size and mass in space.
Scientists estimate it in several ways. Fireball observations give brightness and deceleration, which relate to mass. Infrasound and satellite records give the energy released. Cosmogenic nuclides and fossil tracks in recovered samples show how deeply they were buried inside the original body.
Typical stony meteorites lose most of their mass in the atmosphere. The Chelyabinsk meteoroid of 2013 is estimated to have been about 18 to 20 metres across and around 12,000 tonnes, yet only a few tonnes were recovered, including the largest piece of about 650 kilograms from Lake Chebarkul. Knowing pre-atmospheric sizes helps estimate how much material reaches Earth each year.
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