COULD AN ASTEROID IMPACT EVER CHANGE EARTH'S ORBIT?

Theoretically, any two objects colliding with each other will involve a transfer of momentum that alters their trajectories. So, even a micrometeorite, weighing less than a gram, could result in an imperceptible change in Earth's orbit around the Sun. However, things are not quite that simple.

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Generally, the larger the impacting object the larger the effect of its impact. But the effect depends on many things, for example: the density and tensile strength of the impactor; the geology of the impact point; and the angle and velocity of the impact.