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From Darwin to Mars: Why life's origins are disputed

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Deutsche Welle

<div class="embed-wrap"><figure data-feedback="fb:likes,fb:comments"><img alt="This mosaic of Mars is composed of about 100 Viking Orbiter images. The images were acquired in 1980 during mid-northern summer on Mars. Image by NASA/JPL-Caltech/USGS" src="https://sa.kapamilya.com/absnews/abscbnnews/media/2023/life/08/31/mars-nasa-file.jpg"/><figcaption>This mosaic of Mars is composed of about 100 Viking Orbiter images. The images were acquired in 1980 during mid-northern summer on Mars. <em>Image by NASA/JPL-Caltech/USGS</em></figcaption></figure></div><p>Understanding how life began is one of the most profound areas of science.</p><p>The questions we ask and the answers we find don&#x27;t just help us understand the origins of species on Earth, but also how — or whether — life has existed on the moon or Mars, or extra-terrestrial life exists today farther away in the universe.</p><p>As far as we know, the earliest evidence of life on Earth is a cyanobacteria, dating back 3.7 billion years — about 800 million years after the planet was formed. That evidence was found in fossils in Australia.</p><p>We also know that all known species on Earth are carbon-based life forms.</p><p>Carbon is the primary component of our cells, used by plants to build leaves and stems and by animals for cellular growth and replication.</p><p>But if you&#x27;re wondering where these elementary building blocks of life originated — from space or a swamp? — the answer is manifold and disputed.</p><div><strong>What is Darwin&#x27;s &#x27;primordial soup&#x27; theory?</strong></div><p>Charles Darwin, the British naturalist, thought that life began in &quot;some little warm pond&quot; filled with inorganic chemicals that became complex organic chemicals or molecules. That led to the popular theory of a life-forming primordial soup.</p><p>These organic chemicals began to interact with one another, especially when stabilized and bound in a bag-like membrane.</p><p>Eventually, these cellular structures evolved to become life forms, such as the cyanobacteria found in Australia.</p><p>That&#x27;s the theory, but possibly not the whole truth.</p><ul class="op-related-articles">	<li><a href="https://news.abs-cbn.com/overseas/06/10/22/asteroid-samples-contain-clues-to-origin-of-life-scientists">Asteroid samples contain &#x27;clues to origin of life&#x27;: Japan scientists</a></li></ul><p>&quot;The truth is that those events are almost completely shrouded in mystery. No one knows what sequence of events produced life from non-life, but there are many ideas, ranging from hydrothermal vents on the ocean floor to warm ponds on islands to subsurface environments,&quot; said Silvia Holler, a biochemist at University of Trento, Italy.</p><div><strong>How did hydrothermal vents create early life forms?</strong></div><p>Holler has been studying the earliest beginnings of life, replicating the conditions of hydrothermal vents — hot springs fed by underwater volcanoes — in what she calls chemical gardens.</p><p>Using these chemical gardens, Holler can tweak chemical compositions in a simulated environment — including the amount of energy and level of acid (pH value) — to understand what may have created perfect conditions for the earliest forms of life, or proto-life.</p><p>Holler&#x27;s aim in a study published in the journal PNAS was to understand the stage just before life began, when inorganic chemical structures became organic molecules.</p><p>She found that the structure of hydrothermal vents is crucial for these &quot;chemical transitions.&quot;</p><p>Her research found that when fatty organic molecules are incorporated into the inorganic walls of hydrothermal vents, their structure changes to form vesicles — another bag-like structure that can contain other molecules.</p><p>&quot;Vesicles are similar to primitive cell membranes, or &#x27;proto-cells,&#x27;&quot; said Holler.</p><p>Nick Lane, a professor of evolutionary biology at University College London, UK, was not involved in the research, but said that the findings are important. It shows, said Lane, how cell-like vesicles may have emerged in specific conditions in hydrothermal vents.</p><div><strong>Why is the biology of life still a mystery?</strong></div><p>The vesicles that Holler created are too primitive to be defined as &quot;life&quot; — they didn&#x27;t have any of the recognized processes of life: movement, reproduction, sensitivity, nutrition, excretion, respiration, and growth (simplified in the acronym MRS NERG).</p><p>Lane explained there is a long continuum from very simple prebiotic chemistry to genes and molecular machines that form the complex processes of life. The vesicles in Holler&#x27;s study sit somewhere in the middle.</p><p>The evolution of simple cell-like vesicles, lacking genes, could have evolved relatively &quot;quickly,&quot; said Lane, suggesting a timeframe less than millions of years.</p><p>But the evolution of cells containing DNA genetic code — the stuff that makes us who we are as individuals — probably took hundreds of millions of years, said Lane. And that process would have included life developing ways to create proteins from DNA. Protein is another vital element of life.</p><p>And it&#x27;s this chain of events that remains a mystery.</p><p>Many experiments have tested whether life can arise spontaneously with the presence of organic molecules. But none of the experiments have succeeded in creating life from non-life, said Holler.</p><p>&quot;[W]e can surmise that the gap between organic molecules and life is large, or the molecules themselves are not the key ingredient that causes life to arise,&quot; she said.</p><p>That chimes with Lane&#x27;s view that organic molecules &quot;technically have nothing to do with life — they are just molecules containing hydrogen bound directly to carbon.&quot; Organic molecules may only &quot;appear to be necessary for life,&quot; he said.</p><div><strong>Did life on Earth come from space?</strong></div><p>Another way to test the primordial soup theory lies in our search for extra-terrestrial life.</p><p>Space is full of organic molecules. Molecules dubbed as &quot;probiotic&quot; have been detected in interstellar clouds in distant galaxies, as well as our own Milky Way.</p><ul class="op-related-articles">	<li><a href="https://news.abs-cbn.com/classified-odd/01/31/23/is-there-life-on-mars-maybe-and-it-could-have-dropped-its-teddy">Is there life on Mars? Maybe, and it could have dropped its teddy</a></li>	<li><a href="https://news.abs-cbn.com/spotlight/03/17/21/mars-missing-water-is-buried-beneath-surface-study">Mars&#x27; &#x27;missing&#x27; water is buried beneath surface: study</a></li></ul><p>These probiotic molecules are surprisingly complex, but researchers have yet to find vesicles or cell-like structures in space.</p><p>There is a hypothesis that life came to Earth from space via microscopic organisms that hitched a ride on meteorites or dust particles.</p><p>The idea, known as panspermia, is a fringe theory supported by few scientists, but nevertheless it is intriguing to think that the chemical building blocks required for life may not be unique to Earth.</p><div><strong>Edited by: Zulfikar Abbany</strong></div><p>FROM OUR ARCHIVES</p><figure class="op-interactive"><iframe height="315" src="https://www.youtube.com/embed/q40jpPR0yss?enablejsapi=1" width="560"></iframe></figure><div class="iwantbar">Watch more News on <a href="https://www.iwanttfc.com/#!/browse/Genres/News/tag_id_genres/id_news" target="_blank">iWantTFC</a></div>

Life is a mystery. If it all began in Darwin's earthly primordial soup, how do we explain evidence of the same in space?