Wednesday, December 9, 2020

Formation of organic molecules & “Prebiotic chemistry”

“Prebiotic chemistry” can be understood to mean various things: chemistry which occurred before life began or the chemistry which led to life on Earth, and possibly on other planets. Workers in the field practically define it as naturally occurring, mainly organic, chemistry in planetary or other solar system environments, which may have contributed to the origin of life on Earth, or elsewhere. The terms “abiotic chemistry” (chemistry which takes place in the absence of biology) and “prebiotic chemistry” are in some senses synonymous. Since it is generally assumed that the universe is not goal directed, and since it is not known what processes led to the origin of life, the study of prebiotic chemistry almost certainly includes both productive and nonproductive chemical processes. This review places this chemistry in a historical and cosmic context and details some of the known reactions thought to be important. However, the interested reader is referred to more technical texts (Miller and Orgel 1974; Cleaves 2008; Cleaves and Lazcano 2009) and references therein.
How life on Earth began remains an unexplained scientific problem. This problem is nuanced in its practical details and the way attempted explanations feedback with questions and developments in other areas of science, including astronomy, biology, and planetary science. Prebiotic chemistry attempts to address this issue theoretically, experimentally, and observationally. The ease of formation of bioorganic compounds under plausible prebiotic conditions suggests that these molecules were present in the primitive terrestrial environment. In addition to synthesis in the Earth's primordial atmosphere and oceans, it is likely that the in fill of comets, meteorites, and interplanetary dust particles, as well as submarine hydrothermal vent synthesis, may have contributed to prebiotic organic evolution. The primordial organic soup may have been quite complex, but it did not likely include all of the compounds found in modern organisms. Regardless of their origin, organic compounds would need to be concentrated and complexified by environmental mechanisms.
"Scientists from Japan and the U.S. have confirmed the presence in meteorites of a key organic molecule which may have been used to build other organic molecules, including some used by life. The discovery validates theories of the formation of organic compounds in extraterrestrial environments.
The chemistry of life runs on organic compounds, molecules containing carbon and hydrogen, which also may include oxygen, nitrogen and other elements. While commonly associated with life, organic molecules also can be created by non-biological processes and are not necessarily indicators of life. An enduring mystery regarding the origin of life is how biology could have arisen from non-biological chemical processes, called prebiotic chemistry. Organic molecules from meteorites are one of the sources of organic compounds that lead to the formation of life on Earth."
"An international team of researchers has detected a poly heterocyclic organic molecule called hexamethylenetetramine in three carbonaceous meteorites: Murchison, Murray, and Tagish Lake. The presence of this molecule in carbon-rich meteorites promises its pivotal role to carry interstellar prebiotic precursors to the inner Solar System, which should contribute to the chemical evolution in the primordial stage on Earth.
Presence of organic molecules in extraterrestrial environments has been widely accepted thanks to recent successes in the detection of cometary molecules toward comet 67P/Churyumov-Gerasimenko, as well as long-standing astronomical observations and analyses of carbonaceous meteorites in laboratories.
However, despite extensive studies on the formation of organic molecules in various extraterrestrial environments such as molecular clouds, protosolar nebula and asteroids, it still remains under debate when, where, and how such extraterrestrial molecules were formed."
Thanks
Robert Stonjek, https://evolution-outreach.biomedcentral.com/articles/10.1007/s12052-012-0443-9

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