Changes

Amino acid yield in spark discharge experiments depends critically on the pH of the aqueous phase since at lower pH, amino acid production is greatly reduced and hydroxy acids in greatly increased.<ref name="Bada2013" /> Hydrothermal vents have been proposed as an alternative prebiotic chemistry source but they face severe limitations and actual synthesis have never been demonstrated using plausible geochemical conditions.<ref name="Bada2013" />

Amino acid yield in spark discharge experiments depends critically on the pH of the aqueous phase since at lower pH, amino acid production is greatly reduced and hydroxy acids in greatly increased.<ref name="Bada2013" /> Hydrothermal vents have been proposed as an alternative prebiotic chemistry source but they face severe limitations and actual synthesis have never been demonstrated using plausible geochemical conditions.<ref name="Bada2013" />

====Limited time frames for prebiotic synthesis====

===Limited time frames for prebiotic synthesis===

Scientists believe that there was a time limit for meteorites for form simple to slightly more complex compounds: greater than 1,000 to less than 1,000,000 years.<ref name="Bada2013" /> This poses a problem for hydrothermal vents since they have a very short life span of 100-10,000 years.<ref name="Bada2013" /> Leading Miller-Urey experiment researcher Jeffrey Bada admits:<ref name="Bada2013" />  

Scientists believe that there was a time limit for meteorites for form simple to slightly more complex compounds: greater than 1,000 to less than 1,000,000 years.<ref name="Bada2013" /> This poses a problem for hydrothermal vents since they have a very short life span of 100-10,000 years.<ref name="Bada2013" /> Leading Miller-Urey experiment researcher Jeffrey Bada admits:<ref name="Bada2013" />  

{{Cquote|"An important issue is whether these timescales are compatible with the time required for the transition from abiotic to biotic chemistry. As noted, in carbonaceous meteorites the timescale for amino acid production is between >10³ to <10⁶ years, perhaps even as short as 1–10 years, and there is no evidence that the prebiotic chemistry that took place on the meteorite parent bodies during this aqueous alteration period produced anything beyond simple monomeric compounds. It has been suggested that catalysts such as metal sulfides present in vent systems would promote more rapid synthesis, but by the principle of microscopic reversibility, these must also catalyze the decomposition of any synthesized compounds. Moreover, if this was the case there are certainly potential metal catalysts present on meteorite parent bodies and, as has been indicated, nothing beyond simple molecules were apparently synthesized."}}

{{Cquote|"An important issue is whether these timescales are compatible with the time required for the transition from abiotic to biotic chemistry. As noted, in carbonaceous meteorites the timescale for amino acid production is between >10³ to <10⁶ years, perhaps even as short as 1–10 years, and there is no evidence that the prebiotic chemistry that took place on the meteorite parent bodies during this aqueous alteration period produced anything beyond simple monomeric compounds. It has been suggested that catalysts such as metal sulfides present in vent systems would promote more rapid synthesis, but by the principle of microscopic reversibility, these must also catalyze the decomposition of any synthesized compounds. Moreover, if this was the case there are certainly potential metal catalysts present on meteorite parent bodies and, as has been indicated, nothing beyond simple molecules were apparently synthesized."}}