Did life begin with a bolt from the deep blue?
来源：未知 作者：空断崞 时间：2019-03-07 04:16:03
By Jon Evans LIFE may really have been created by a spark, one that came as a bolt from the deep blue. Hydrothermal vents on the deep ocean floor are believed by many to be the cradle for early life. Now a team led by Ryuhei Nakamura at the University of Tokyo in Japan have uncovered evidence that such vents can generate electrical currents. They say these currents could have helped generate the complex carbon-based molecules that came together to produce life, as well as provide it with a handy power supply. Vents bring minerals containing iron, copper and sulphur from deep inside the Earth’s crust to the seabed. The minerals possess an excess of electrons, so Nakamura’s team wanted to find out whether these electrons could generate an electric current in the vent. To do this, they carried out the first lab-based electrical experiments on a type of sulphur-rich chimney known as a black smoker. The chimney was extracted from a hydrothermal vent in the middle of the South Pacific Ocean. First, the team passed a current through the chimney wall to show that it could conduct electricity. Next, they simulated the conditions at a hydrothermal vent by pumping hot, sulphur-rich water past one side of a chimney wall, and cold, salty water past the other. This generated a weak but steady electrical current across the chimney wall (Angewandte Chemie, DOI: 10.1002/anie.201003311). Hot, sulphur-rich water flowing through a sea-floor vent generates a weak electrical current The team thinks that the chimney walls catalyse the conversion of sulphides into elemental sulphur as the hot vent fluid travels through them. The reaction releases electrons which pass through the wall to the salt water outside, where they convert dissolved oxygen into hydrogen peroxide. Nakamura postulates that this electrical current could provide a source of energy for bacteria. Nick Lane, a biochemist who studies hydrothermal vents at University College London, says the findings are “interesting and curious”, but points out that there was hardly any oxygen around in the primordial ocean to sustain the current. Nakamura suggests that carbon dioxide took the place of oxygen. If this was the case, then the CO2 would have been converted directly into carbon-based molecules, making complex organic molecules on the early Earth’s sea floors – perhaps the chemical precursors of life. The next step, they say, is to confirm that black smokers generate electricity when they are at the bottom of the ocean, not just in the lab. More on these topics: