The Polar spacecraft carries two cameras which are capable of viewing Earth's far-ultraviolet dayglow. One of these two cameras was programmed into a special operating mode during 12 April and 30 July 1996 in order to obtain simultaneous images of transient decreases of dayglow emissions from atomic oxygen at 130.4 nm. During the 76 minutes of usable imaging the two cameras acquired five sets of frames for which a transient decrease was detected by each camera, and the transient decrease occurred at the same geographical position in the dayglow. These series of observations provide strong evidence for the identification of atmospheric holes as a geophysical phenomenon. ¿ 1997 American Geophysical Union