March 11, 2004 — Spirit came across a surprise as it gazed upward: a streak across the sky. The streak, seen in the middle of this mosaic of images taken by the navigation and panoramic cameras, was probably the brightest object in the sky at the time. Scientists theorize that the mystery line could be either a meteorite or one of seven out-of-commission spacecraft still orbiting Mars. Of all of the Mars orbiters, only Viking 1 and 2 could produce motion as fast as that seen by Spirit.