We describe the geological, morphological, and climatic setting of the San Juan meteorite collection area in the Central Depression of the Atacama Desert (Chile). Our recovery activities yielded 48 meteorites corresponding to a minimum of 36 different falls within a 3.88 km(2) area. The recovery density is in the range 9-12 falls km(-2) depending on pairing, making it the densest among meteorite collection areas in hot deserts. This high meteorite concentration is linked to the long-standing hyperaridity of the area, the stability of the surface pebbles (> Ma), and very low erosion rates of surface pebbles (approximately 30 cm Ma(-1) maximum). The San Juan meteorite population is characterized by old terrestrial ages that range from zero to beyond 40 ka, and limited weathering compared with other dense collection areas in hot desert. Chemical weathering in San Juan is slow and mainly controlled by the initial porosity of meteorites. As in the Antarctic and other hot deserts, there is an overabundance of H chondrites and a shortage of LL chondrites compared with the modern falls population, suggesting a recent (< few ka) change in the composition of the meteorite flux to Earth

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We summarize the use of radiocarbon produced by spallation in meteorites in space to determine their terrestrial age or residence time. This "age" gives us important information as it can be compared to the rates of weathering and infall of meteorites. The processes that affect the collection of meteorites in a given area can be related to the rates of infall of new meteorites, and the rate of removal by chemical weathering and physical erosion.