The sizes, shapes, and surface or subsurface properties of Near Earth Objects (mostly asteroids, also inactive comet nuclei) are still poorly known, since any accurate determination requires in situ missions. It may nevertheless be estimated that the sizes of these irregular bodies range from a few tens of kilometres to a few tens of meters, with possibly about 1000 NEOs with sizes greater than 1 km. Their surfaces are estimated to be quite rough, and at least partially covered with regolith. To cite this article: A.C. Levasseur-Regourd et al., C. R. Physique 6 (2005).
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