If such bombardment has really been occurring, scientists would have to rethink the origins of the earth's oceans, terrestrial life, and the formation of the solar system. Our moon could not escape the icy-comet bombardment. Roughly 1,000 craters 50 meters in diameter and splashes of debris 150 meters in diameter must occur each . There is no evidence that the moon is thus afflicted.
Comets also carry the noble gases argon, krypton, and xenon.
These gases should accumulate in the atmosphere as the comets disintegrate. The amounts of these gases actually measured are 10,000 times less than those the postulated bombardment would produce. The icy comets should break up near the earth and produce clouds of ice crystals. Sunlight reflected from such 30-ton clouds would be brighter than Venus and easily visible before they disperse. Such objects are rarely seen, implying that small icy comets do not exist in the numbers claimed.