Fragmentation
Fragmentation is the breaking up of a meteoroid into many pieces as it passes through the atmosphere.
A meteoroid ploughing through the atmosphere faces rising air pressure on its front. Rocks are rarely perfect: they contain cracks, weak veins and loosely stuck-together fragments. When the pressure outstrips the strength of the weakest parts, the body breaks. Each new piece may then break again, in a cascade called fragmentation.
Fragmentation shapes what reaches the ground. A single strong body may land as one stone, while a fragile one may shower down as thousands. On 30 January 1868, a meteoroid broke up over Pułtusk in Poland and scattered a huge number of small stones, many of them no bigger than peas, over a wide area. Fragmentation also causes the bright flares seen in many fireballs, because each burst exposes fresh surfaces to the heat.
Pieces that broke off late in flight may show a thin, less developed crust on one face, called secondary crust, while broken edges that formed after the glowing stopped have no crust at all. Collectors and scientists use these clues to piece together a meteorite's breakup history.
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Level: Explorer Ages 10 and up