Bombardment of the Hadean Earth: Wholesome or deleterious?

Graham Ryder died in January 2002 at the age of 53. He was a Staff Scientist at the Lunar and Planetary Science Institute in Houston, TX for most of his professional life, studying lunar petrology and planetary impacts. For many years he was the senior editor of the Proceedings of the Lunar and Planetary Science Conference, and he was the senior editor of Geological Society of America Special Paper 307, The Cretaceous-Tertiary Event and Other Catastrophes in Earth History. He was the major advocate for the 3.8 Ga lunar impact cataclysm and was just beginning to publish on correlations of the early lunar impact record to that of the other inner planets at the time of his death. Graham's abstract to the Rubey Colloquium was never presented. Although Graham made many of the points in this abstract to lunar science audiences, he certainly would have wanted these views to be shared with the Astrobiology community. We have taken the liberty of publishing this abstract with the Rubey proceedings, with only a few minor revisions to include reference to some recently published papers. These revisions were recommended by Gary R. Byerly, who reviewed this abstract for publication.