How do Jupiter’s gravitational resonances help send asteroid fragments toward Earth?

Jupiter’s gravitational influence sends asteroid fragments toward Earth primarily through mean-motion resonances, which create regions of low density in the asteroid belt known as Kirkwood gaps.12

When an asteroid fragment enters one of these gaps—such as the prominent 3:1 resonance—it completes a simple fraction of orbits for every single revolution made by Jupiter. Because the asteroid and Jupiter return to the same relative positions at regular intervals, the asteroid experiences repeated gravitational "nudges" in a fixed direction.132

These consistent perturbations cause the fragment's orbit to become chaotic, gradually shifting its perihelion (the point in its orbit closest to the Sun) until it crosses Earth’s orbit. This process is a highly efficient mechanism for injecting material into Earth-crossing paths, far exceeding the effectiveness of direct collisional ejection. To maintain this supply of material, other processes, such as the Yarkovsky effect, help drift smaller fragments into these resonant zones.341