- 3419 - SUPERNOVAE - responsible for life on Earth? Supernova activity might be necessary for life to exist. Nucleo-synthesis occurs when supernova explosions forge heavy chemical elements necessary for life. Supernovae explosions create and spread elements like iron out into space to be taken up during the formation of stars and planets.
--------------------- 3419 - SUPERNOVAE - responsible for life on Earth?
- It’s almost impossible to comprehend a supernova explosion’s violent, destructive power. An exploding supernova can outshine its host galaxy for a few weeks or even months. That seems almost impossible when considering that a galaxy can contain hundreds of billions of shining stars.
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- Any planet too close to a supernova would be completely sterilized by all the energy released, its atmosphere would be stripped away, and it may even be shredded into pieces.
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- However, a certain amount of supernova activity might be necessary for life to exist. Nucleo-synthesis occurs when supernova explosions forge heavy chemical elements necessary for life. Supernovae explosions create and spread elements like iron out into space to be taken up during the formation of stars and planets. Without them, you wouldn’t be reading this.
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- Supernova activity in Earth’s neighborhood may have led to more oxygen in the atmosphere. And oxygen is necessary for complex life. The oxygen is at the end of a long chain of cause and effect, and it all begins with the “Galactic Cosmic Rays” (GCR) released by supernovae.
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- Life on Earth appears to have evolved under the influence of supernovae activity in the solar neighborhood. There is a connection between climate, clouds, and cosmic rays from supernovae. When heavy stars explode, they produce cosmic rays made of elementary particles with enormous energies.
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- Cosmic rays travel to our solar system, and some end their journey by colliding with Earth’s atmosphere. They are responsible for ionizing the atmosphere. The ionizing energy from those cosmic rays creates aerosols in Earth’s upper atmosphere.
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- That increases cloud formation. Clouds block solar radiation from reaching Earth’s surface, cooling the climate. A cooler climate has greater temperature differences between polar regions and mid-latitudes. Those differences create stronger winds and ocean currents, which in turn drive stronger nutrient cycles.
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- There is a correlation between supernova rates and trace elements, or nutrients, in the ocean. The nutrients are found in pyrite and are a proxy for nutrients in the ocean. The climatic warm periods , cold periods , glacial periods , and finally peak glaciations all contribute to life’s evolution.
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- Stronger nutrient cycles mean that more chemical elements necessary for life are delivered to the upper 200 meters of the ocean, near continental shelves, where bio-productivity is highest.
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- When there’s higher bio-productivity, more organisms live and die, and when they die, they fall to the ocean floor as organic matter, to be encased in sediments.
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- On geological time scales, supernovae activity can fluctuate wildly, by several hundred percent. So the effect on climate can be pronounced on long time scales. Supernova activity over time can be compared to the increased levels of organic matter that result from supernovae.
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- The frequency of supernova explosions comes from star cluster data and open cluster data from previous studies. The correlation is clearer for the last 500 million years and is less clear the further back they look.
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- So how does the increased organic matter lead to more oxygen? The organic matter in ocean sediments in the form of Carbon 12. Life prefers the lighter C12 isotope over C13, and the ratio of C12 to C13 in the sediments reveals the presence of life over geological timescales.
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- All of this activity has consequences for Earth’s oxygen. When organic matter moves into sediments, it becomes an indirect source of oxygen. If all of that organic matter were exposed to the atmosphere, then it would react with atmospheric oxygen as it decomposed and pull the oxygen out of the atmosphere. Instead, since the organic matter is buried, the oxygen remains in the atmosphere. And complex life needs oxygen.
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- This wouldn’t happen without nearby supernova and the cosmic rays they produce. Without enough nearby supernova activity, the climate would be warmer. The winds and ocean currents would be weaker, and would move fewer nutrients around.
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- The strong upwelling ocean currents required to deliver chemical nutrients to the ocean’s bioproductive zone would be absent. The consequence of a warmer climate would be less bioproductivity because ocean currents and atmospheric winds would be weaker.
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- Less bioproductivity would mean less organic material (C12) in the ocean sediments. The available kinetic energy in the ocean-atmosphere system determines the mixing and transport of nutrients in the oceans and atmosphere.
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- All those currents combine to create “thermohaline circulation“, also called the ocean conveyor belt. That belt, along with winds and surface run-off from rivers,. drives Earth’s nutrient cycle.
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- A consequence is that moving organic matter to sediments is indirectly the source of oxygen. Photosynthesis produces oxygen and sugar from light, water and CO2. However, if organic material is not moved into sediments, oxygen and organic matter become CO2 and water.
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- The burial of organic material prevents this reverse reaction. Therefore, supernovae indirectly control oxygen production, and oxygen is the foundation of all complex life.
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- Oxygenic photosynthesis and organic matter burial is the primary source of oxygen, and oxygen underpins the evolution of complex life. The new evidence points to an extraordinary interconnection between life on Earth and supernovae, mediated by the effect of cosmic rays on clouds and climate.
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- Clearly, supernova activity and life on Earth come down to dosage. Some supernovae have been close enough to Earth to contribute to partial extinction.
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- A supernova explosion may have triggered the Ordovician Extinction, the second-largest extinction in Earth’s history by number of species killed off. And if one were too close, it would sterilize Earth completely. But according to this research some supernovae activity helped drive life on Earth by stimulating the nutrient cycle and increasing atmospheric oxygen.
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- We’re accustomed to thinking of nearby supernovae as potentially devastating to life on Earth, and they are. If there were no supernova activity in our neighborhood, life on Earth might look much different than it does now. Did a supernova cause the Devonian mass extinction event?
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- 359 million years ago the Earth suffered one of its worst extinction events which might have be caused by a series of supernova explosions no more than 35 light years away.
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- Every once in a while something disastrous happens to life on Earth. The biggest episodes we call extinction events. The latest big one happened about 65 million years ago, and was a very rough time for dinosaurs.
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- But that extinction event was just the latest in a long series of interruptions in the multitude of life on the planet. One of the earliest extinction events happened at the boundary of the Devonian and Carboniferous periods about 359 million years ago.
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- We’re not exactly sure what triggered that extinction event. There’s no clear smoking gun like there is for the asteroid impact evidence of the one that killed most of the dinosaurs. The key piece of evidence leading to this hypothesis is the fact that fossils of plants remaining from that tumultuous era show signs of nasty sunburns, excess UV exposure.
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- The ozone layer of the Earth does a fantastic job of blocking almost all the UV radiation from the sun, so the fact that these critters were getting an extra dose means that our ozone layer had to be depleted. There are a lot of potential geological processes that can scrub away our ozone layer, and there’s also one celestial one.
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- The intense radiation from a close enough supernova blast can strip away our ozone, leaving the surface of the Earth exposed to the UV onslaught from the sun. Intense UV radiation is harmful for living beings causing an extinction event.
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- The researchers estimated that a single supernova blast within 65 light years could have been enough to suppress our ozone layer for about 100,000 years. The fossil record indicates that life was having a tough go at it for three times that length, however, so the researchers speculate that the supernova wasn’t alone. Stars do tend to cluster and big stars do tend to go off as supernova relatively close by.
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- Research is working to find evidence in those fossil layers of an excess of certain radioactive elements like plutonium-244. This element isn’t naturally produced on the Earth, and so the only way for it to exist in that layer of sediment is for it to have been put there as the shock-wave of the supernova washed over our planet.
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- The nearest supernova candidate to the Earth is the star Betelgeuse, which is located a safe 600 light years away.
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January 18, 2022 SUPERNOVAE - responsible for life on Earth? 3419
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