Water, Thermodynamics and Insight
Water, life’s solvent, is the current yardstick by which scientists use to characterize earthly life and is in part the basis for understanding the “Goldilocks zone.” As a result of life’s watermark, it is often assumed that where there is life—water is nearby. That statement, by itself, is more complex than most can appreciate. Early earth did not have “enough” of life’s present necessities—one primary element comes to mind, reduced phosphorous. When one looks for phosphorus—the primary form that is found is in oxidized form. Chemistry, as we know it, needs reduced phosphorus to readily form the phosphate groups in RNA and DNA. The elementary chemistry of nucleotides (that of RNA and DNA) is notoriously difficult in the laboratory—so much so that science at present cannot hope to fully elucidate the origin of life. The oceans of the early earth were far more conducive to forming life’s early molecules and possibly even more so at or around hydrothermal vents (a source of heat energy).
Reduced phosphorus is found in sedimentary layers of the Earth’s crust—and is a predominant mineral found in SNC –meteorites (meteorites that are primarily carbonaceous chondrules that contain iron-nickel-phosphorus minerals). The chemical nature of phosphorus on earth is such that it is in the predominantly oxidized form—as chemical thermodynamics dictates. Thus, examination of phosphorus “thermodynamic phase diagrams” indicates that early earth conditions (specifically during the Archean)—favored the reaction of reduced phosphorus with prebiotic soup of the time period.
In papers by Pasek and others, mounting evidence may point toward the Late Heavy Bombardment of the Archean era as one likely source for reduced phosphorus. Through the sampling of “archean sedimentary rock” it seemed as if prebiotic conditions were conducive to RNA-world life. The reasons for the hypothesis are time of the Late Heavy Bombardment, and presence of schreibersite (nickel-iron-phosphorus containing) meteoritic material in the sedimentary layers. Although further evidence is warranted so as to be conclusive, layers of sediment from Australia are indicative of reduced phosphorus being present.
(At the time of this writing, Dr. Steven Benner at University of Florida announced the intriguing hypothesis that life may owe its origins to Mars due to the relative paucity of water, and readily available metal ions needed stabilize early nucleotides; e.g. RNA and DNA.)—It should be noted that most SNC-meteorites originate from Martian crust.
Pasek, Matthew a, Jelte P Harnmeijer, Roger Buick, Maheen Gull, and Zachary Atlas. 2013. “Evidence for Reactive Reduced Phosphorus Species in the Early Archean Ocean.” Proceedings of the National Academy of Sciences of the United States of America 110 (25) (June 18): 10089–94. doi:10.1073/pnas.1303904110. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3690879&tool=pmcentrez&rendertype=abstract.
Pasek, Matthew a. 2008. “Rethinking Early Earth Phosphorus Geochemistry.” Proceedings of the National Academy of Sciences of the United States of America 105 (3) (January 22): 853–8. doi:10.1073/pnas.0708205105. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2242691&tool=pmcentrez&rendertype=abstract.
Citations regarding Dr. Benner’s announcement:
Pale Blue Blog– Men are from Mars and Women are from Mars, too? By: S. DOMAGAL-GOLDMAN. http://www.astrobio.net/paleblueblog/?p=2067.
The Guardian– Life on earth ‘began on Mars’ Geochemist argues that seeds of life originated on Mars and were blasted to Earth by meteorites or volcanoes. By: Press Association. http://www.theguardian.com/science/2013/aug/29/life-earth-originated-mars