The origin of Apollo-Amor objects.

Although Apollo-Amor asteroids have been regarded as plausible candidates for extinct comets, their aphelia are well inside Jupiter's orbit, unlike those of short-period comets. This aphelion reduction is difficult to explain by Whipple's jet effect. Hence the author hypothesis that encounters with the earth or Venus have reduced the aphelion distances. It is found that there is a remarkable agreement between the Jacobi constants of A-A objects and those of hypothetical comets that dip inside or graze the orbits of the earth or Venus.