The Small‐Comet Hypothesis

摘要: According to the small-comet hypothesis, small comets strike Earth approximately 20 times per minute, each comet nominally containing 100 tons (105 kg) of water-ice. The primary observations interpreted as evidence for these are dark spots in Earth's atomic-oxygen UV dayglow seen by imager on Dynamics Explorer (DE) satellite. These must disintegrate near and then sublimate within a few seconds, water vapor expanding form clouds vapor, 50 km diameter, that temporarily block spacecraft's view dayglow, thus producing spots. In this review we examine problems basic mechanisms underlying hypothesis. include inconsistencies with known geophysical phenomena, conflicting results from independent searches presence comets, hypothesis itself. No other interpretation can account DE has been advanced. only viable alternative literature is nongeophysical one—the instrument-artifact hypothesis—in which it proposed appear randomly pictures. Tests both qualitative statistical, show it, neatly economically, explains dark-spot data. Owing weight accumulated against lack credible supporting evidence, plausibility unlikely valid.