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Why can Amor asteroids become Earth crossers over time?

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The Chicxulub asteroid — Earth impact hazard An artist's rendering of the impact of a near-Earth object 66 million years ago in what is today the Caribbean region. Many scientists think that the collision of a large asteroid or comet nucleus with Earth triggered the mass extinction of dinosaurs and many other species near the end of the Cretaceous Period.

Amor asteroids are a class of near-Earth asteroids characterized by perihelion distances between 1.017 AU (Earth's aphelion) and 1.3 AU. While they do not currently cross Earth's orbit, they can become Earth-crossers over time due to strong gravitational perturbations caused by their close approaches to Earth.

These gravitational interactions cause the orbital elements of these asteroids to change appreciably on timescales as short as years or decades. Consequently, about half of the known Amor asteroids are considered part-time Earth-crossers. This dynamic evolution is a significant factor in the study of the Earth impact hazard, as these objects may eventually transition into orbits that intersect with Earth's path, potentially leading to a collision or ejection from the solar system.6