The most feature of the orbits of Near Earth Asteroids(NEAs) is that the semi major axes of the orbits are nearly equal to that of the Earth or the perihelia distances are approximate to or even less than the mean distance between the Sun and the Earth,thus they could move into inside of the Earth s orbit,so that th.
近地小行星轨道的最大特点是其轨道半长径与地球轨道半长径相近 ,或近日距离接近甚至小于日地平均距离 ,其运动可深入到地球轨道的内部 ,这将导致该类小行星与地球 (还有金星、火星等 )十分靠近甚至发生碰撞 。