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It is widely believed that life originated in water. However, there is no standard model about the origin of life. Some of the models without water (or having important substances other than water) are listed below. | It is widely believed that life originated in water. However, there is no standard model about the origin of life. Some of the models without water (or having important substances other than water) are listed below. | ||
The "deep-hot biosphere" model says that life first developed not on the surface of the Earth, but several kilometers below the surface. The discovery in the late 1990s of nanobes in deep rock might be seen as evidence. It is now well established that microbial life is plentiful up to 5km below the surface | The "deep-hot biosphere" model says that life first developed not on the surface of the Earth, but several kilometers below the surface. The discovery in the late 1990s of nanobes in deep rock might be seen as evidence. It is now well established that microbial life is plentiful up to 5km below the surface of the Earth.<ref name="nanobe">{{cite web | url=http://www.microscopy-uk.org.uk/index.html?http://www.microscopy-uk.org.uk/nanobes/nanobes.html | title=Nanobes–Intro | last= | first= | work= | publisher=microscopy-uk.org | accessdate=2008-01-14 }}</ref> | ||
The "Zn-World" model postulates that zinc salts have the unique ability to store radiation energy, e.g. provided by UV light which was 10 to 100 times more intense than now and provided the ideal energy conditions for the synthesis of informational and metabolic molecules. The primordial atmosphere was rich in carbon dioxide and the chemistry of water condensates and exhalations near geothermal fields would resemble that of modern cells. Ionic composition conducive to the origin of cells is shown to be more compatible with emissions of zones that have today become inland geothermal systems than with marine settings. The precellular stages of evolution may have taken place in shallow "Darwin-ponds" lined with porous silicates, metal sulfides, zinc, potassium, and phosphorus compounds.<ref>{{cite journal | last1=Mulkidjanian | first1=A. Y. | last2=Bychkov | first2=A. Y. | last3=Dibrova | first3=D. V. | last4=Galperin | first4=M. Y. | last5=Koonin | first5=E. V. | year=2012 | title=Origin of first cells at terrestrial, anoxic geothermal fields | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=109 | pages=E821–30 | doi=10.1073/pnas.1117774109 | issue=14 | pmid=22331915 | pmc=3325685 |bibcode=2012PNAS..109E.821M }}</ref><ref>For a deeper integrative version of this hypothesis see {{cite book | last=Egel | first=R. | editor-last=Lankenau | editor-first=D.-H. | editor2-last=Mulkidjanian, | editor2-first=A. Y. | year=2011 | title=Origins of Life: The Primal Self-Organization | publisher=Springer | isbn=978-3-642-21625-1}}, in particular {{cite book| last=Lankenau | first=D.-H. | chapter=Two RNA Worlds: Toward the Origin of Replication, Genes, Recombination and Repair | title=Origins of Life: The Primal Self-Organization| publisher=Springer | publication-date=2011 | isbn=978-3-642-21625-1 | pages=225–286 }}, interconnecting the "Two RNA worlds" concept and other detailed aspects; and {{cite journal | last1=Davidovich | first1=C. | last2=Belousoff | first2=M. | last3=Bashan | first3=A. | last4=Yonath | first4=A. | year=2009 | title=The evolving ribosome: from non-coded peptide bond formation to sophisticated translation machinery | journal=Res Microbiol | volume=160 | pages=487–492 | doi=10.1016/j.resmic.2009.07.004 | issue=7 }}</ref> | The "Zn-World" model postulates that zinc salts have the unique ability to store radiation energy, e.g. provided by UV light which was 10 to 100 times more intense in the distant past than now and provided the ideal energy conditions for the synthesis of informational and metabolic molecules. The primordial atmosphere was rich in carbon dioxide and the chemistry of water condensates and exhalations near geothermal fields would resemble that of modern cells. Ionic composition conducive to the origin of cells is shown to be more compatible with emissions of zones that have today become inland geothermal systems than with marine settings. The precellular stages of evolution may have taken place in shallow "Darwin-ponds" lined with porous silicates, metal sulfides, zinc, potassium, and phosphorus compounds.<ref>{{cite journal | last1=Mulkidjanian | first1=A. Y. | last2=Bychkov | first2=A. Y. | last3=Dibrova | first3=D. V. | last4=Galperin | first4=M. Y. | last5=Koonin | first5=E. V. | year=2012 | title=Origin of first cells at terrestrial, anoxic geothermal fields | journal=Proceedings of the National Academy of Sciences of the United States of America | volume=109 | pages=E821–30 | doi=10.1073/pnas.1117774109 | issue=14 | pmid=22331915 | pmc=3325685 |bibcode=2012PNAS..109E.821M }}</ref><ref>For a deeper integrative version of this hypothesis see {{cite book | last=Egel | first=R. | editor-last=Lankenau | editor-first=D.-H. | editor2-last=Mulkidjanian, | editor2-first=A. Y. | year=2011 | title=Origins of Life: The Primal Self-Organization | publisher=Springer | isbn=978-3-642-21625-1}}, in particular {{cite book| last=Lankenau | first=D.-H. | chapter=Two RNA Worlds: Toward the Origin of Replication, Genes, Recombination and Repair | title=Origins of Life: The Primal Self-Organization| publisher=Springer | publication-date=2011 | isbn=978-3-642-21625-1 | pages=225–286 }}, interconnecting the "Two RNA worlds" concept and other detailed aspects; and {{cite journal | last1=Davidovich | first1=C. | last2=Belousoff | first2=M. | last3=Bashan | first3=A. | last4=Yonath | first4=A. | year=2009 | title=The evolving ribosome: from non-coded peptide bond formation to sophisticated translation machinery | journal=Res Microbiol | volume=160 | pages=487–492 | doi=10.1016/j.resmic.2009.07.004 | issue=7 }}</ref> | ||
There is also a "Primitive extraterrestrial organisms" model, which finds support in the studies of Martian meteorites found in Antarctica and in studies of some microbes' survival in outer space.<ref>{{cite web | url=http://www.newscientist.com/channel/life/evolution/dn2844 | title=Tough Earth bug may be from Mars | publisher=New Scientist |date=25 September 2002 }}</ref><ref>{{cite web | url=http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1992-049B-03 | title=Exobiology and Radiation Assembly (ERA) | year=1992 | work=[[ESA]] | publisher=NASA }}</ref><ref name="Gerda Horneck">{{cite journal | doi=10.1128/MMBR.00016-09 | title=Space Microbiology | year=2010 | last1=Horneck | first1=G. | last2=Klaus | first2=D. M. | last3=Mancinelli | first3=R. L. | journal=Microbiology and Molecular Biology Reviews | volume=74 | pages=121–56 | pmid=20197502 | issue=1 | pmc=2832349 }}</ref><ref name="Clancy">{{cite book | last1=Paul Clancy | title=Looking for Life, Searching the Solar System | publisher=Cambridge University Press | date=23 June 2005 }}{{page needed|date=November 2013 }}</ref><ref name="Rabbow">{{cite journal | title=EXPOSE, an Astrobiological Exposure Facility on the International Space Station – from Proposal to Flight | journal=Orig Life Evol Biosph | date=9 July 2009 | first=Elke | last=Rabbow | first2=Gerda | last2=Horneck | first3=Petra | last3=Rettberg | first4=Jobst-Ulrich | last4=Schott | first5=Corinna | last5=Panitz | first6=Andrea | last6=L'Afflitto | first7=Ralf | last7=von Heise-Rotenburg, | first8=Reiner| last8= Willnecker | first9=Pietro | last9=Baglioni | first10=Jason | last10=Hatton, | first11=Jan | last11=Dettmann | first12=René | last12=Demets | first13=Günther | last13=Reitz | doi=10.1007/s11084-009-9173-6 | volume=39 | issue=6 | pages=581–98 | pmid=19629743 | bibcode=2009OLEB...39..581R }}</ref><ref>{{cite journal | title=Survival of Rock-Colonizing Organisms After 1.5 Years in Outer Space | journal=Astrobiology | date=May 2012 | first=Silvano | last=Onofri | first2=Rosa | last2=de la Torre | first3=Jean-Pierre | last3=de Vera | first4=Sieglinde | last4=Ott | first5=Laura | last5=Zucconi | first6=Laura | last6=Selbmann | first7=Giuliano | last7=Scalzi | first8=Kasthuri J. | last8=Venkateswaran | first9=Elke | last9=Rabbow, | first10=Francisco J. | last10=Sánchez Iñigo | first11=Gerda | last11=Horneck | volume=12 | issue=5 | pages=508–516 | doi=10.1089/ast.2011.0736 | pmid=22680696 | bibcode=2012AsBio..12..508O }}</ref><ref name=Beer>{{cite news | last=Amos | first=Jonathan | title=Beer microbes live 553 days outside ISS | url=http://www.bbc.co.uk/news/science-environment-11039206 | publisher=BBC News | work=Science and Technology | date=23 August 2010 }}</ref> Studies which apply the equivalent of Moore's Law to evolution have proposed that life began 9.7 billion years ago, billions of years before the Earth was formed. Life may have started "from systems with single heritable elements."<ref name="arXiv-20130328">{{cite journal |last1=Sharov |first1=Alexei A. |last2=Gordon|first2=Richard |title=Life Before Earth |url=http://arxiv.org/ftp/arxiv/papers/1304/1304.3381.pdf | format=PDF |date=28 March 2013 |journal=[[arXiv]] |arxiv=1304.3381v1 }}</ref><ref name="NIH-20060612">{{cite journal |last=Sharov |first=Alexei A. |title=Genome increase as a clock for the origin and evolution of life |journal=[[Biology Direct]] |volume=1 |pages=1–17 |date=12 June 2006 |issue= |doi=10.1186/1745-6150-1-17 |pmc=1526419 }}</ref> | There is also a "Primitive extraterrestrial organisms" model, which finds support in the studies of Martian meteorites found in Antarctica and in studies of some microbes' survival in outer space.<ref>{{cite web | url=http://www.newscientist.com/channel/life/evolution/dn2844 | title=Tough Earth bug may be from Mars | publisher=New Scientist |date=25 September 2002 }}</ref><ref>{{cite web | url=http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1992-049B-03 | title=Exobiology and Radiation Assembly (ERA) | year=1992 | work=[[ESA]] | publisher=NASA }}</ref><ref name="Gerda Horneck">{{cite journal | doi=10.1128/MMBR.00016-09 | title=Space Microbiology | year=2010 | last1=Horneck | first1=G. | last2=Klaus | first2=D. M. | last3=Mancinelli | first3=R. L. | journal=Microbiology and Molecular Biology Reviews | volume=74 | pages=121–56 | pmid=20197502 | issue=1 | pmc=2832349 }}</ref><ref name="Clancy">{{cite book | last1=Paul Clancy | title=Looking for Life, Searching the Solar System | publisher=Cambridge University Press | date=23 June 2005 }}{{page needed|date=November 2013 }}</ref><ref name="Rabbow">{{cite journal | title=EXPOSE, an Astrobiological Exposure Facility on the International Space Station – from Proposal to Flight | journal=Orig Life Evol Biosph | date=9 July 2009 | first=Elke | last=Rabbow | first2=Gerda | last2=Horneck | first3=Petra | last3=Rettberg | first4=Jobst-Ulrich | last4=Schott | first5=Corinna | last5=Panitz | first6=Andrea | last6=L'Afflitto | first7=Ralf | last7=von Heise-Rotenburg, | first8=Reiner| last8= Willnecker | first9=Pietro | last9=Baglioni | first10=Jason | last10=Hatton, | first11=Jan | last11=Dettmann | first12=René | last12=Demets | first13=Günther | last13=Reitz | doi=10.1007/s11084-009-9173-6 | volume=39 | issue=6 | pages=581–98 | pmid=19629743 | bibcode=2009OLEB...39..581R }}</ref><ref>{{cite journal | title=Survival of Rock-Colonizing Organisms After 1.5 Years in Outer Space | journal=Astrobiology | date=May 2012 | first=Silvano | last=Onofri | first2=Rosa | last2=de la Torre | first3=Jean-Pierre | last3=de Vera | first4=Sieglinde | last4=Ott | first5=Laura | last5=Zucconi | first6=Laura | last6=Selbmann | first7=Giuliano | last7=Scalzi | first8=Kasthuri J. | last8=Venkateswaran | first9=Elke | last9=Rabbow, | first10=Francisco J. | last10=Sánchez Iñigo | first11=Gerda | last11=Horneck | volume=12 | issue=5 | pages=508–516 | doi=10.1089/ast.2011.0736 | pmid=22680696 | bibcode=2012AsBio..12..508O }}</ref><ref name=Beer>{{cite news | last=Amos | first=Jonathan | title=Beer microbes live 553 days outside ISS | url=http://www.bbc.co.uk/news/science-environment-11039206 | publisher=BBC News | work=Science and Technology | date=23 August 2010 }}</ref> Studies which apply the equivalent of Moore's Law to evolution have proposed that life began 9.7 billion years ago, billions of years before the Earth was formed. Life may have started "from systems with single heritable elements."<ref name="arXiv-20130328">{{cite journal |last1=Sharov |first1=Alexei A. |last2=Gordon|first2=Richard |title=Life Before Earth |url=http://arxiv.org/ftp/arxiv/papers/1304/1304.3381.pdf | format=PDF |date=28 March 2013 |journal=[[arXiv]] |arxiv=1304.3381v1 }}</ref><ref name="NIH-20060612">{{cite journal |last=Sharov |first=Alexei A. |title=Genome increase as a clock for the origin and evolution of life |journal=[[Biology Direct]] |volume=1 |pages=1–17 |date=12 June 2006 |issue= |doi=10.1186/1745-6150-1-17 |pmc=1526419 }}</ref> |