A group of asteroids that cross the orbit of Mars, but not that of Earth; also known as Earth-approaching (or Earth-grazing) asteroids. Their orbits have perihelia between 1.017 AU (Earth's aphelion distance) and 1.3 AU (the perihelion of Mars). Close approaches to Mars and Earth can turn Amors into Earth-crossers (see Apollo Group) temporarily, and vice versa (see also Near-Earth Asteroid). The group is named after (1221) Amor, diameter 1 km, discovered in 1932 by the Belgian astronomer Eugène Joseph Delporte (1882–1955). Amor's orbit has a semimajor axis of 1.921 AU, period 2.66 years, perihelion 1.09 AU, aphelion 2.76 AU, and inclination 11°.9. Amor group members show a broad variety of compositional types, evidently having originated from several sources. Asteroids may be perturbed into Amor-type orbits either by Jupiter, from near the 3 : 1 and 5 : 2 Kirkwood gaps in the main asteroid belt, or by Mars, from near the inner edge of the main belt. The two largest members of the Amor group are the S-class (1036) Ganymed, diameter 32 km, and Eros.
Subjects: Astronomy and Astrophysics.