 
        
        	Is life common in the universe, or rare? Humans have pondered this question for millennia.
In this Astronomy Talk, Dr. Carl Pilcher, Interim Director of the NASA Astrobiology Institute, will help us study the four billion-year evolution of life and our planet to consider how habitable environments and life itself might arise elsewhere in the Universe.
 Widespread Mixing and Burial of Earth’s Hadean Crust by Asteroid Impacts
                    
                    Widespread Mixing and Burial of Earth’s Hadean Crust by Asteroid Impacts NASA Astrobiology Debates: Eastern Championship Live Webcast
                    
                    NASA Astrobiology Debates: Eastern Championship Live Webcast NASA Astrobiology Debates: Western Championship Live Webcast
                    
                    NASA Astrobiology Debates: Western Championship Live Webcast NASA/Library of Congress Astrobiology Symposium
                    
                    NASA/Library of Congress Astrobiology Symposium