Posted by Cole McElMurray
The origin of life is a hotly debated topic. Many competing theories still abound in the field of science over where and how the first living organism arose, whether on Earth or somewhere else in the universe. However, one recent discovery points to the possibility of life arising in extreme conditions: specifically, in terrestrial hot springs such as the ones found in Yellowstone National Park. Jack Lee of Science News reports that Drs. David Deamer and Bruce Damer of the University of California, Santa Cruz have found evidence that hot springs provide the necessary conditions for syntheses of organic molecules to proceed.
Figure 1: Hydrothermal hot spring, Hell’s Gate, New Zealand. This site was used by Damer for experimentation.
A condensation reaction is a simple organic reaction that removes water from any OOH group, such as a carboxylic acid or phosphate, and a neighboring hydroxyl group, to link them in an ester bond. Condensation reactions are important in biology to not only form lipid chains, but to link nucleotides in RNA and DNA. These reactions in living cells are catalyzed by enzymes, but Dr. Damer hypothesized that these reactions could occur in situ in a hot, wet environment such as a hot spring. To test the theory, he prepared vials with the precursors to RNA before placing them in a metal block which was then lowered into a hydrothermal pool at around 100 degrees Celsius. Measured quantities of hot spring water were transferred to the vials before letting the materials dry, simulating the tides of the primordial Earth. This pattern was repeated several times. At the end of the experiments, long chains of nucleotides had formed, lending support to Damer’s hypothesis that these reactions were likely to occur in hot springs such as the kind that were prevalent early in the Earth’s history.
Figure 2: Condensation reaction of a triglyceride, an important type lipid found in the body.
The scientists’ theory is not without its detractors. Dr. Laurie Barge of the Jet Propulsion Laboratory in Pasadena, California, finds that the conditions of underwater hydrothermal vents produces condensation reactions of RNA nucleotides. However, Deamer believes that the cycle of evaporation and saturation is the most important key to the natural formation of long-chain organic molecules, and contends that the dilution of molecules in the ocean as well as the high salt content inhibits the reactions that would drive the formation of the precursors to life.
The evidence of life’s origin under these conditions lends itself not only to the study of life on Earth, but to extraterrestrial life as well. Evidence has been found on Jupiter’s moon Europa and Saturn’s moon Enceladus of hydrothermal activity in the forms of plumes of water vapor erupting from underneath the icy surface. In addition, Barge postulates that the freezing and thawing of ice on these moons could emulate the cycle of dehydration and rehydration as an analogue to the tidal cycle of the primordial Earth that Deamer and Damer studied. The two, on the other hand, prefer to focus on Mars, where geological evidence suggests that hydrothermal hot springs were found millions of years ago.
Figure 3: Artist’s rendition of water vapor plumes on Europa.
The article in Science News, being written for a crowd of both scientists and laymen with a vested interest in interesting discoveries and new theories, takes an overall neutral view of the subject. It reports and details both Deamer and Damer’s hypothesis and research results, as well as competing theories like that of Barge, and does not endorse any particular view, instead leaving it up to the reader to decide. While the article makes note that the chemical reactions that drive the formation of important biological molecules are the key to the scientists’ discoveries, it does not go into extreme
detail about what the reactions are, instead preferring to explain them as simply as possible so as not to bore readers.
Sources:
https://www.sciencenews.org/article/life-earth-origins-hostile-hot-springs-microbes
https://resources.stuff.co.nz/content/dam/images/1/r/3/5/i/i/image.related.StuffLandscapeSixteenByN ine.710x400.1r30ig.png/1533337202027.jpg
Chemistry, 3rd edition (Tro) https://www.sciencealert.com/images/2019-11/processed/EuropaWaterPlumesConfirmed_1024.jpg
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