Image of Earth's dayglow at ultraviolet wavelengths, primarily atomic oxygen emissions at 130.4 nm, showing several severe, transient decreases of intensities. One of these atmospheric "holes" is shown in expanded view in the inset. The ring of emission at the top of this image is the northern auroral oval. This image was taken with Dynamics Explorer 1 from an altitude of 18,500 km at 1640 UT on 20 October 1981. The geographic latitude and longitude of the spacecraft position are 41° and 242°, respectively. These atmospheric holes are interpreted in terms of the influx of comet-like objects with masses about 10⁸ gm, i.e., 100 tons, into Earth's upper atmosphere.