Meteorite "Falls" vs. "Finds"
There is also a major caveat when extrapolating from meteorites to asteroids. Most meteors break apart, disperse or burn up in Earth's atmosphere. Volatile rich meteors usually explode due to heating during the fiery atmospheric entry. Soft and crumbly chondrites would be expected to break apart often, even if they were volatile poor. Irons and stony irons punch through intact much more commonly than other meteors.
Those which wind up in laboratories come in two categories: "finds" and "falls":
"Finds" are meteorites which were found on the ground unrelated to any sighting, due to the finder recognizing them to be clearly identifyable as being of nonterrestrial origin.
"Falls" are meteorites which were seen to fall from the sky and which were tracked down successfully. Meteorites found on top of the snow in Antarctica are also classified as finds. Some finds come from rooftops and the like. A few have come from cars and the street.
The main advantage of Antarctic meteorites is that everything on the snow must be a meteorite, not an Earth rock, which eliminates bias of recognition of an object. The Antarctic Meteorite Research Center (see link below) has statistics on meteorite types found in the Antarctic. As of 2012, this is 86% chondrites, 7% achondrites, 6% irons, and 1% stony irons.
There have been well organized efforts to collect Antarctic meteorites over the decades, especially from the 1970s to date. Of particular interest is areas where the ice is melting, evaporating, or just getting blown away, leaving a concentration of meteorites behind.
The only way to eliminate bias according to soft meteors (such as from extinct comets) disintegrating up in the atmosphere vs. hard ones reaching the ground is by going to asteroids themselves with a space probe.
Before going to asteroids, analysts must rely on studies performed by analyzing the light reflected off the surfaces of asteroids.
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