This Science magazine News article discusses a new scenario for early earth history that is claimed to explain the earth's surface metal distribution and that it could effect conditions affecting the origin of life. This was before the end of the heavy late bombardment (timeline diagram in article) when many large impactors are thought to have hit the earth. This is then claimed to result in a hydrogen rich atmosphere due to: Reducing conditions are often considered favorable for life origin conditions because they favor the production of increasingly more complex organic molecules which life depends upon. The article then elaborates on how this hydrogen atmosphere might have lead to the earlier production of RNA components and lead to an early "RNA world" which has been hypothesized to be the precede the current situation where DNA predominates as the information carrier of most life forms. Because RNA molecules can have both biological information properties as well as enzymatic properties (ribozymes), they are thought to be good candidates for early informational molecules. They would embody their own enzymatic properties instead of having to rely upon a complex system of making proteins from RNA sequence to produce the early enzymatic properties that life is thought to have required. I'm guessing a more reduced atmosphere would also favor the production of other kinds of organic molecules also, like lipids, amino acids, sugars. They also discussed alternative possible explanations: early stages of life could also have been based upon a combination of RNA's and proteins (RNA/protein world hypothesis?), and that some the early establishment of metabolism would have been important to initiating living processes (metabolism first hypothesis). There are several different issues of the origin of life problem, among which are: When and under what chemical conditions did life first form? Where did the origin of life "action" took place (warm pond, hot ocean vents, warm ocean vents (different chemistry), salt water laces that could under go wet-dry cycles, mineral rich fresh water places that could undergo wet-dry cycles, ocean bottom, on pyrite crystals, or in clay, and probably others)? What were the physical/chemical drivers of the proto-cell's metabolism? What was the molecular basis of early enzymatic activities (RNA, proteins, surfaces of crystals or ceramics, nickle/iron/sulfur/?? compounds)? What was the source and importance of the establishment of the cell membrane? What was the order in which these different traits evolved? Different scenarios have been proposed which deal with these issues in different ways. These are different competing hypotheses with potentially partially overlapping explanatory components which makes comparisons between the alternative scenarios difficult. Although interesting, some of the explanations in this article for certain aspects of the overall explanation are not the only proposed hypotheses to deal with the issues listed above.