The origin of life Presented by: Arzhang Davazdahemami

Overview: Introduction Spontaneous generation Scientific hypothesis  Reduced atmosphere  Meteorite compact  Hot sea vent conclusion

Introduction Earth; the only known place for living creatures He is ~4.5 billion years old ~500 million years subjected to bombardment of meteorites After a few million years the life began

Introduction The oldest microfossil ever seen is 3.5 years old Our investigate in rocks formation estimate the time of 3.8 million years ago What is the source of small organic molecules?

Overview: Introduction Spontaneous generation Scientific hypothesis  Reduced atmosphere  Meteorite compact  Hot sea vent conclusion

Spontaneous generation Until early 19th there was a believe that living creatures can form from non living matter Ignorance of spontaneous creation by Pastor experiments which comes up with evolution theory of Darwin Beginning of theoretical hypothesis about creation…

Overview: Introduction Spontaneous generation Scientific hypothesis  Reduced atmosphere  Meteorite compact  Hot sea vent conclusion

Reduced atmosphere A hypotheses which based on an atmosphere with small amount of oxygen in 3.8 million years ago It was a popular hypotheses in early 20th and attracted lots of scientist The most ingredients of atmosphere was: Methane, Water vapor, Ammonia, Hydrogen Miller and Urey started the new era of astrobiology by the means of an experiment which was a module for cycle of rain in 3.5 million years ago

Miller-Urey experiment

Result

Table Amount of amino acids in Murchison meteorite and products of Miller experiment are roughly the same

Facts… Although the modulus of Miller-Urey works properly to introduce the first step of appearance of life on earth by showing that sugars are made from formaldehydes, there was estimate in their experiment which is really small amount of oxygen. And in these days we believe that atmosphere was not that much reduced…

Overview: Introduction Spontaneous generation Scientific hypothesis  Reduced atmosphere  Meteorite compact  Hot sea vent conclusion

Meteorite 4 billion years ago earth was under meteorites bombardment One of those groups of meteorites are carbonaceous chondrites Interesting because of their organic carbon, standard amino acids and nucleic acid

Facts Supporter of this hypothesis think that there was enough organic carbon to start the process of prebiotic synthesis. But the question is would that organic materials survive according to intensive heat of entering the atmosphere? The result of this hypothesis is completely based on assumption about  Density of the atmosphere  Composition of the atmosphere  Size of the meteorite  Components of the meteorite  Etc.

Overview: Introduction Spontaneous generation Scientific hypothesis  Reduced atmosphere  Meteorite compact  Deep-sea vents conclusion

Deep-sea vents There is a ideal place for biological activity because of independency of sun light There is a reaction of iron(II) sulfide and hydrogen sulfide which release free energy necessary to reduction of carbon dioxide to organic molecules In this hypothesis there is a assumption that  This complex metabolism would organize itself  And the products of that metabolism never escape from surface

Deep-sea vents Stetter and colleagues showed that hydrogen sulfide with iron(II) would work as reducing agent  Acetylene to ethane  Mercaptoacetic acid to acetic acid  But no reduction of CO2 Afterward new studies show that there is a possibility to reduce carbon monoxide when FeS spiked with NiS Carbon monoxide might have been present in the gases escaped from vents If metal sulfides can be shown to catalyze the synthesis of organic molecules, the vent hypothesis would become popular as a origin of biomers…

Conclusion There are lots of hypothesis that introduce origin of life. some of them are popular, lots of them not. None of them are proven but also not expelled. The work nowadays is to use more than one source to show how does the life begin…

References Orgel, L. E. (1998) Trends in biochem. Sci. 12, Orgel, L. E. (1998) Origin of life evol. 1, Orgel, L. E. (1994) Sci. Am. 4, Kumar, A. (2008) Astrophys. Space Sci. 317,