Xenoforce

From the introduction:

Before an effective infiltration could be mounted, disaster struck. During one of the early reconnaissance probes of the Earth, one of the probe ships was struck by lightning over the deserts of New Mexico. The alien pilot became momentarily disoriented and the probe ship struck the ground. The bottom of the spacecraft was torn off, destroying its control circuitry. The craft bounced back into the air due to its inertia and flew on for a few kilometers more before striking the face of an exposed desert mesa. It was July, 1947, and the first time aliens had landed on our planet. It would not be the last time.