  All near-Earth asteroids (NEAs) that reach sufficiently small perihelion
distances will undergo a so-called super-catastrophic disruption. The
mechanisms causing such disruptions are currently unknown or, at least,
undetermined. To help guide theoretical and experimental work to understand the
disruption mechanism, we use numerical simulations of a synthetic NEA
population to identify the resonant mechanisms that are responsible for driving
NEAs close to the Sun, determine how these different mechanisms relate to their
dynamical lifetimes at small heliocentric distances and calculate the average
time they spend at different heliocentric distances. Typically, resonances
between NEAs and the terrestrial and giant planets are able to dramatically
reduce the perihelion distances of the former. We developed an algorithm that
scans the orbital evolution of asteroids and automatically identifies
occurrences of mean motion and secular resonances. We find that most near-Sun
asteroids are pushed to small perihelion distances by the 3:1J and 4:1J
mean-motion resonances with Jupiter, as well as the secular resonances v6,
v5,v3 and v4. The time-scale of the small-perihelion evolution is fastest for
the 4:1J, followed by the 3:1J, while v5 is the slowest.~7% of the test
asteroids were not trapped in a resonance during the latest stages of their
dynamical evolution, which suggests that the secular oscillation of the
eccentricity due to the Kozai mechanism, a planetary close encounter or a
resonance that we have not identified pushed them below the estimated average
disruption distance.
