- 3469 - LIFE - a mystery to behold? The origin of life on Earth began more than 3,000,000,000 years ago, evolving from the most basic of microbes into a dazzling array of complexity over time. But how did the first organisms on the only known home to life in the universe develop from the primordial soup?
--------- Life in a drop of water
------------------------------ 3469 - LIFE - a mystery to behold?
- Science remains undecided and conflicted as to the exact origin of life, also known as “abiogenesis“. Even the very definition of life is contested and rewritten, with one study published in the Journal of Biomolecular Structure and Dynamics, suggesting uncovering 123 different published definitions.
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- Lightning may have provided the spark needed for life to begin. Electric sparks can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia and hydrogen, as was shown in the famous Miller-Urey experiment in 1952.
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- The experiment's findings suggested that lightning might have helped create the key building blocks of life on Earth in its early days. Over millions of years, larger and more complex molecules could form.
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- Although research since then has revealed the early atmosphere of Earth was actually hydrogen-poor, scientists have suggested that volcanic clouds in the early atmosphere might have held methane, ammonia and hydrogen and been filled with lightning as well.
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- The first molecules of life might have met on clay. Clay crystals preserve their structure as they grow and stick together to form areas exposed to different environments and trap other molecules along the way and organize them into patterns much like our genes do now.
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- The main role of DNA is to store information on how other molecules should be arranged. Genetic sequences in DNA are essentially instructions on how amino acids should be arranged in proteins. Mineral crystals in clay could have arranged organic molecules into organized patterns. After a while, organic molecules took over this job and organized themselves.
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- The deep-sea vent theory suggests that life may have begun at submarine hydrothermal vents spewing elements key to life, such as carbon and hydrogen. Hydrothermal vents can be found in the darkest depths of the ocean floors, typically on diverging continental plates.
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- These vents erupt fluid which is superheated by the Earth’s core as it passes up through the crust, before being ejected at the vets. During its journey through the crust it collects dissolved gases and minerals, such as carbon and hydrogen.
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- Their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reactions. Even now, these vents, rich in chemical and thermal energy, sustain vibrant ecosystems.
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- Abiogenesis by way of hydrothermal vents continues to be investigated as a plausible cause of life on Earth. In 2019, scientists at University College London, successfully created protocells (non-living structures that help scientists understand the origins of life) under similar hot, alkaline environmental conditions to hydrothermal vents.
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- Ice might have covered the oceans 3 billion years ago and facilitated the birth of life. Key organic compounds thought to be important in the origin of life are more stable at lower temperatures.
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- At normal temperatures these compounds, such as simple sets of amino acids, are sparsely populated in water, but when frozen become concentrated and facilitate the emergence of life.
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- Ice also might have protected fragile organic compounds in the water below from ultraviolet light and destruction from cosmic impacts. The cold might have also helped these molecules to survive longer, enabling key reactions to happen.
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- DNA needs proteins in order to form, and proteins require DNA to form, so how could these have formed without each other? The answer may be RNA, which can store information like DNA, serve as an enzyme like proteins, and help create both DNA and proteins. Later DNA and proteins succeeded this "RNA world," because they are more efficient.
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- RNA still exists and performs several functions in organisms, including acting as an on-off switch for some genes. The question still remains how RNA got here in the first place. Some scientists think the molecule could have spontaneously arisen on Earth, while others say that was very unlikely to have happened.
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- Instead of developing from complex molecules such as RNA, life might have begun with smaller molecules interacting with each other in cycles of reactions. These might have been contained in simple capsules akin to cell membranes, and over time more complex molecules that performed these reactions better than the smaller ones could have evolved, scenarios dubbed "metabolism-first" models, as opposed to the "gene-first" model of the "RNA world" hypothesis.
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- Could life have been delivered to Earth from space? Perhaps life did not begin on Earth at all, but was brought here from elsewhere in space, a notion known as “panspermia“.
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- For instance, rocks regularly get blasted off Mars by cosmic impacts, and a number of Martian meteorites have been found on Earth that some researchers have controversially suggested brought microbes over here, potentially making us all Martians originally.
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- Other scientists have even suggested that life might have hitchhiked on comets from other star systems. However, even if this concept were true, the question of how life began on Earth would then only change to how life began elsewhere in space. God only knows?
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February 18, 2022 LIFE - a mystery to behold? 3469
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