title: Impacts and the origin of life.
abstract: As living creatures, all of us have some interest in the question of how life originated.  To some, the question is more religious than scientific; nonetheless, a small but dedicated group of scientists spend their careers trying to answer it from a rational standpoint.  Logically, the question can be broken down into the three standard divisions of any mystery:  When did life originate?  Where did it originate?  And how did it originate?  Of these three sub-questions the last is by far the most difficult and I will make no attempt to address it here.  I will however take a personal look at the two easier parts of the problem.  In particular, I will outline my current view of the physical environment of the early Earth, and I will try to show how observations of other solar system bodies, especially our own Moon, provide clues as to when and where life could have originated.
authors.affiliation: The Pennsylvania State University, College of Earth and Mineral Sciences, University Park, USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Kasting
mesh_terms: D001272:Atmosphere; D005075:Biological Evolution; D002245:Carbon Dioxide / Q000032:analysis; D002254:Carbonates / Q000032:analysis; D018534:Earth, Planet; D008962:Models, Theoretical; D016081:Moon; D009792:Oceans and Seas; D000069497:Origin of Life; D017640:Silicates / Q000032:analysis; D016082:Solar System; D013455:Sulfur / Q000032:analysis; D013696:Temperature
chemical_list: D002254:Carbonates; D017640:Silicates; D002245:Carbon Dioxide; D013455:Sulfur