一些证据表明,地球原始大气层中还原分子的含量可能比Miller-Urey实验时所认为的要少。有大量的证据表明,40亿年前的大型火山爆发会向大气中释放二氧化碳、氮、硫化氢(H<sub>2</sub>S)和二氧化硫(SO<sub>2</sub>) <ref name=Green>{{Cite journal|last=Green|first=Jack|title=Academic Aspects of Lunar Water Resources and Their Relevance to Lunar Protolife|journal=International Journal of Molecular Sciences|year=2011|volume=12|issue=9|pages=6051–6076|doi=10.3390/ijms12096051|pmid=22016644|pmc=3189768|ref=harv}}</ref>。除了最初的Miller-Urey实验中使用的气体之外,进一步使用这些气体的实验产生了更多样化的分子。该实验创造了一种外消旋体(包含L和D对映异构体)的混合物。此后的实验表明,“在实验室中,这两种化合物出现的可能性相等” <ref name="NS">{{Cite news |date=2006-06-02 |title=Right-handed amino acids were left behind |periodical=[[New Scientist]] |publisher=Reed Business Information Ltd |issue=2554 |pages=18 |url=https://www.newscientist.com/channel/life/mg19025545.200-righthanded-amino-acids-were-left-behind.html |accessdate=2008-07-09 |url-status=live |archiveurl=https://web.archive.org/web/20081024211531/http://www.newscientist.com/channel/life/mg19025545.200-righthanded-amino-acids-were-left-behind.html |archivedate=2008-10-24 }}</ref> ; 然而,在自然界中,L氨基酸占主导地位。后来的实验证实了不成比例的L或D取向对映异构体是可能的<ref>{{cite journal |last=Kojo |first=Shosuke |first2=Hiromi |last2=Uchino |first3=Mayu |last3=Yoshimura |first4=Kyoko |last4=Tanaka |date=October 2004 |title=Racemic D,L-asparagine causes enantiomeric excess of other coexisting racemic D,L-amino acids during recrystallization: a hypothesis accounting for the origin of L-amino acids in the biosphere |journal=Chemical Communications |volume= |issue=19 |pages=2146–2147 |pmid=15467844 |doi=10.1039/b409941a}}</ref> | 一些证据表明,地球原始大气层中还原分子的含量可能比Miller-Urey实验时所认为的要少。有大量的证据表明,40亿年前的大型火山爆发会向大气中释放二氧化碳、氮、硫化氢(H<sub>2</sub>S)和二氧化硫(SO<sub>2</sub>) <ref name=Green>{{Cite journal|last=Green|first=Jack|title=Academic Aspects of Lunar Water Resources and Their Relevance to Lunar Protolife|journal=International Journal of Molecular Sciences|year=2011|volume=12|issue=9|pages=6051–6076|doi=10.3390/ijms12096051|pmid=22016644|pmc=3189768|ref=harv}}</ref>。除了最初的Miller-Urey实验中使用的气体之外,进一步使用这些气体的实验产生了更多样化的分子。该实验创造了一种外消旋体(包含L和D对映异构体)的混合物。此后的实验表明,“在实验室中,这两种化合物出现的可能性相等” <ref name="NS">{{Cite news |date=2006-06-02 |title=Right-handed amino acids were left behind |periodical=[[New Scientist]] |publisher=Reed Business Information Ltd |issue=2554 |pages=18 |url=https://www.newscientist.com/channel/life/mg19025545.200-righthanded-amino-acids-were-left-behind.html |accessdate=2008-07-09 |url-status=live |archiveurl=https://web.archive.org/web/20081024211531/http://www.newscientist.com/channel/life/mg19025545.200-righthanded-amino-acids-were-left-behind.html |archivedate=2008-10-24 }}</ref> ; 然而,在自然界中,L氨基酸占主导地位。后来的实验证实了不成比例的L或D取向对映异构体是可能的<ref>{{cite journal |last=Kojo |first=Shosuke |first2=Hiromi |last2=Uchino |first3=Mayu |last3=Yoshimura |first4=Kyoko |last4=Tanaka |date=October 2004 |title=Racemic D,L-asparagine causes enantiomeric excess of other coexisting racemic D,L-amino acids during recrystallization: a hypothesis accounting for the origin of L-amino acids in the biosphere |journal=Chemical Communications |volume= |issue=19 |pages=2146–2147 |pmid=15467844 |doi=10.1039/b409941a}}</ref> |