Small Comets and Our Origins: The Ecstacy and Agony of the Scientific Debate

Small Comets and Our Origins:  The Ecstacy and Agony of the Scientific Debate A Presidential Lecture given by University of Iowa Carver/James A. Van Allen
Professor of Physics
Louis A. Frank
 
It is a shocking notion. Radiation-blasted, black- jacketed snowballs the size of houses swarming out of the cosmic void every day, plowing into Earth's atmosphere and pancaking explosively into clouds of vapor that fall as gentle rains.
 

Over billions of years these invaders might have filled Earth's oceans and provided the seeds of life.

 
-Kathy Sawyer Astronomy(October 1998)