It's exciting that a guy who was pretty badly pilloried is going to be vindicated, at least as far as the observations are concerned. Both Donahue and Meier caution that the new observations do not necessarily confirm Frank's original hypothesis, with all its sweeping implications. It is unclear, for instance, exactly what these objects are. These things look like comets, and they quack like comets. If the small objects were comets, their gradual evaporation should have added significantly to the amount of hydrogen in the space between Earth and Mars.
Scientists detect no such enrichment.
To circumvent this problem, Frank has proposed that the snowballs are covered with a carbon skin that keeps them from vaporizing until they get within 2,000 kilometers of Earth, close enough for gravity or electrical forces to tear them apart. The new data have not silenced all of Frank's former critics. Until an independent team confirms the observations, Dessler says, he will remain doubtful. For instance, scientists studying the moon have found no evidence of craters created by the impact of these snowballs. What's more, seismic detectors left on the moon by Apollo astronauts have not detected any crashes of the hypothesized bodies, even though each would equal a 15-kiloton blast, says Dessler.