Influx of small comets into Earth's atmosphere

摘要

Approximately 11 years ago unexpected transient decreases of Earth's dayglow intensities with spatial dimensions of approximately 50 km in diameter were detected in the first high-resolution global images from a high-altitude orbiting spacecraft, Dynamics Explorer 1. These decreases in dayglow intensities were measured in an ultraviolet spectral window that is very sensitive to absorption by water molecules and clusters along the camera's line-of-sight from the spacecraft to the sunlit atmosphere. These decreases exhibited several features that indicated an extraterrestrial source. Namely (1) preferential motion in the east-to-west direction across the sunlit face of Earth, (2) similar diurnal variations in occurrence rates as those for radar meters, (3) correlation of the occurrence rates with the nonshower rates as determined with forward scatter radar, and (4) larger angular diameters for these atmospheric holes as the altitude of the spacecraft decreases. The only viable interpretation of these atmospheric holes to date is the impact of incoming water clouds from small comets that have disrupted in the vicinity of Earth. The startling consequence of this interpretation is an influx of about 20 small comets each minute into our atmosphere, each with a mass of tens of tons. These measurements and interpretation inspired a heated debate which resulted in dismissing the small comets because the observations were generally obtained at the imager's threshold. A new ultraviolet imager with more than 100 times the resolution of the Dynamics Explorer-1 camera has been recently flown on the Polar spacecraft. These images from the Polar camera confirm the existence of the small comets. A mission to further investigate the composition and dynamics of these small comets is suggested.