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An accelerated video of a miniature hydrothermal chimney being formed in the laboratory, as in the early Earth Ocean. Natural vents can continue to form for thousands of years and reach a height of several tens of meters. Credit: NASA / JPL-Caltech / Flores
Scientists have reproduced in the laboratory how the ingredients of life could have formed at the bottom of the ocean 4 billion years ago. The results of the new study provide clues as to how life began on Earth and where we could find it elsewhere in the cosmos.
Astrobiologist Laurie Barge and her team at NASA's Jet Propulsion Laboratory in Pasadena, California, use to recognize life on other planets by studying the origins of life here on Earth. Their research focuses on how the building blocks of life are formed in hydrothermal vents at the bottom of the ocean.
To recreate the hydrothermal vents in the lab, the team created its own miniature seabed by filling cups with mixtures mimicking the Earth's primordial ocean. These laboratory oceans act as nurseries for amino acids, organic compounds essential to life as we know it. Like Lego blocks, amino acids build on each other to form proteins, which make up all living things.
"Understanding where one can go with just organic matter and minerals before having a real cell is really important to understand what types of environments life could emerge from," said Barge, the principal investigator and the first author of the new study, published in the newspaper Proceedings of the National Academy of Sciences. "In addition, examining the impact of factors such as the atmosphere, the ocean, and the minerals in the vents can help you understand the likelihood that this will occur on another planet."
Located around cracks in the seabed, hydrothermal vents are places where natural chimneys form, releasing heated fluid under the earth's crust. When these chimneys interact with the seawater that surrounds them, they create a constantly changing environment, essential to the evolution of life. This dark and hot environment powered by the Earth's chemical energy can be the key to forming life on more distant worlds in our solar system, away from the heat of the Sun.
"If we have these hydrothermal vents on Earth, similar reactions could possibly occur on other planets," said Erika Flores, co-author of the new study at JPL.
Barge and Flores used in their experiments ingredients that are commonly found in the first oceans of the Earth. They combined the water, the minerals and the "precursor" pyruvate and ammonia molecules needed to start the formation of amino acids. They tested their hypothesis by heating the solution to 70 ° C (the same temperature as that found near a hydrothermal vent) and adjusting the pH to mimic the alkaline environment. They also removed the oxygen from the mix because, unlike today, the early Earth had very little oxygen in its ocean. The team also used the mineral iron hydroxide, or "green rust," which was abundant on the early Earth.
Green rust reacted with small amounts of oxygen that the team injected into the solution, producing the amino acid alanine and the alpha-hydroxy acid lactate. Alpha-hydroxy acids are byproducts of amino acid reactions, but some scientists believe that they could also combine to form more complex organic molecules that can lead to life.
"We have shown that in geological conditions similar to those of the early Earth and perhaps to other planets, we can form amino acids and alpha-hydroxy acids from a simple reaction in soft conditions that would have existed on the seabed, "said Barge.
The creation by Barge of amino acids and alpha-hydroxy in the laboratory is the culmination of nine years of research on the origins of life. Previous studies have aimed to determine whether hydrothermal vents contain the right ingredients for life and to determine how much energy these vents can generate (enough to power a light bulb). But this new study is the first time his team observes an environment very similar to a hydrothermal vent and triggers an organic reaction. Barge and his team will continue to study these reactions in the hope of finding more ingredients for life and creating more complex molecules. Step by step, she slowly climbed the chain of life.
Laurie Barge, left, and Erika Flores, right, at the JPL Origins and Habitability Laboratory in Pasadena, California. Credit: NASA / JPL-Caltech
This line of research is important to the extent that scientists study the worlds of our solar system and beyond that can host habitable environments. The moon of Jupiter Europa and the moon of Saturn Enceladus, for example, could have hydrothermal vents in the oceans under their icy crusts. Understanding how life could begin in an ocean without sunlight would help scientists design future exploration missions, as well as experiments that can dig under the ice to look for traces of amino acids or other amino acids. other biological molecules.
Future missions on Mars could return samples of the rusty surface of the red planet, which could reveal traces of amino acids formed by iron minerals and ancient water. Exoplanets – worlds beyond our reach but still in the realm of our telescopes – can carry in their atmosphere signatures of life that could be revealed in the future.
"We have not yet concrete evidence of life elsewhere," Barge said. "But understanding the conditions that are necessary at the beginning of life can help to narrow the places where we think life could exist."
This research was funded by the JPL Icy Worlds team from the NASA Astrobiology Institute.
Explore further:
Experiments on hydrothermal vents bring Enceladus to Earth
More information:
Laura M. Barge et al. Gradients of redox and pH determine the amino acid synthesis in mineral iron oxide oxyhydroxide systems, Proceedings of the National Academy of Sciences (2019). DOI: 10.1073 / pnas.1812098116
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