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Published online by Cambridge University Press: 12 April 2016
Close-approach asteroids, members of the so-called Apollo and Amor groups, are of considerable current interest as potential targets for probes and also in connection with the question of identification of the parent bodies of the meteorites. The possibility that some of these asteroids may be surviving comet nuclei has been suggested earlier. (See, e.g., Öpik, 1963.) Relatively few objects of this type are known; all are small bodies found accidentally in the course of work not always related to investigations of minor planets. The known Apollo and Amor asteroids, and notes as to their present observational status, are listed in table I. (See also table II of Marsden.) Except when they are relatively close to Earth (many can approach within 0.10 AU), these objects are faint and often in very awkward positions as well, low in the evening or morning sky at twilight.