oceans

Ships have been damaging the oceans with noise for centuries. Germany is working on silent propellers to solve it

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Every time a boat crosses the seas, it is accompanied by a continuous noise underwater: that of the propellers that propel it. The noise problem of propellers in marine ecosystems is identified academically since 2004, but its reason for being is even older: the first time they analyzed its cause It was in 1893. What there is no solution to that disturbing low-frequency sound that spreads for kilometers, disturbing fish, cetaceans and other marine living beings. And its reason for being is even older: the first time cavitation was analyzed was in 1893. A team from the Kiel University of Applied Sciences has set out to remedy it with its project MinKav. Brief notes on cavitation. To understand the problem, we must first see what happens to the blades of a propeller when they rotate at high speed. With their movement, the blades generate a pressure difference between their faces. Thus, on the back side the pressure drops so much that the water changes state, going from liquid to gas. More specifically, thousands of small vapor bubbles. The problem is when these bubbles leave that low pressure zone: they then implode violently, returning to the liquid state, which causes pressure waves that are transmitted at high speed through the water. If the waves collide with a surface, they can deteriorate it considerably. The phenomenon of cavitation is accompanied by vibration and noise, as if it were gravel falling on a machine. This sound is broadband, with low frequency components capable of traveling long distances. Why is it important. Of all possible aquatic pollution, human-caused acoustics are the least mainstream, but their effects are documented. A couple of concrete examples of the importance of sound for aquatic species: whales They use sound to communicate, orient themselves and huntthe fish for such essential tasks how to detect predators or spawning and crustaceans are sensitive to vibration in the background. To get an idea of ​​the magnitude of the problem, according to the International Chamber of Navigation There are approximately 50,000 merchant ships operating continuously around the planet and they all emit that sound. It is not something specific. And the research team adds a twist: a propeller with less cavitation is not only less noisy, it can also potentially be more efficient (cavitation is wasted mechanical energy). Less noise and fewer emissions. The discovery. The HAW Kiel team has identified when the problem originates: the sound peak does not occur when the bubble forms, but right at the end of the collapse. And its intensity depends directly on the speed at which this collapse occurs. The faster you go, the stronger the blow. Illustration of human, marine animal and environmental sound sources in the marine environment, with proportional sound waves. National Office of Oceanic and Atmospheric Administration How are they doing it. The experiments are being carried out at the Naval Hydrodynamics Laboratory of the German university, in a kind of aquarium with a miniature propeller, so that they can reproduce the flow conditions around the propeller. Equipped with underwater microphones and high-speed cameras, they have determined where and when that noise peak occurs. The next step is computer simulations to experiment with designing different propeller geometries to reduce noise without sacrificing performance, efficiency or durability. The most obvious solution, lowering the rpm, is not an option: a commercial boat cannot afford to go slower. Pending subjects. However, MinKav started in January of this year, will last three years and have a budget of 390,000 euros, modest for a problem of global scale. Even if MinKav were to come to fruition, it would have to go from the laboratory to scale-up on a commercial ship. In Xataka | A Spaniard has patented a mast that transforms wind and waves into electricity: his invention challenges diesel in boats In Xataka | A “roomba” to clean rivers: the ship that the Three Gorges Dam has launched in China Cover | Pexels

The origin of the oceans on Earth has always been somewhat mysterious. Now we are clearer how it happened

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A team of scientists, analyzing the tiny and invaluable samples of the asteroid Ryugu brought to Earth by the Hayabusa2 missionhas made a discovery that shakes our understanding of water in the early solar system. The discovery, published in the prestigious magazine Naturereveals that liquid water flowed in Ryugu’s progenitor body more than a billion years after its formation. Something that changes our paradigms. Contradiction. This new discovery contradicts the belief that water activity on asteroids It was a phenomenon exclusive to the first moments of the history of our solar system. And most importantly, it could force us to recalculate how much water these bodies brought to a young Earth. Many doubts. The story of how our planet became an aquatic world still has gaps. One of the most accepted theories is that carbonaceous asteroidsformed from ice and dust in the confines of the Solar Systemacted as a cosmic “water delivery” service for the inner planets. JAXA’s Hayabusa2 mission has provided us with a unique opportunity to study this process by bringing back 5.4 grams of pure material from the asteroid Ryugu. And this is very important. While meteorites that fall to Earth are altered by contact with the atmosphere and environment, the Ryugu samples are a near-perfect time capsule. This is because a perfect record of water activity is preserved within it, proof that fluids moved through its rocks sooner than could be expected. This is something fundamental that changes the way we think about where the water in asteroids comes from and ends up on our planets. Isotopic clock. To reach this conclusion, the team turned to a “radiometric dating“based on isotopes: the radioactive decay of Lutetium-176 into Hafnium-176. Something that can be similar to the ‘Carbon-14’ test that is better known. In an object as old as Ryugu’s father, you would expect the proportion of these elements to follow a predictable line, known as isochronewhich dates back to 4,565 million years ago. But Ryugu’s data did not fit these models. The samples deviated from that ‘reference’ line showing an excess of hafnium (or a deficiency of lutetium). In order to understand why, it was first ruled out that it was due to accelerated disintegration or the effects of cosmic radiation. This made the conclusion point differently than that, at some point, a liquid ‘washed’ and took away some of the lutetium from the asteroid’s rocks. The reasons. The event that triggered this late flow of water was, most likely, a violent impact. While the first aqueous activity, which occurred in the first seven million years of the solar system, was driven by heat from the decay of radioactive elements, this second event was different. Specifically, we are talking about an impact on the body of Ryugu’s ‘father’ that would have generated enough heat to melt the ice that had remained frozen inside for eons, and at the same time, would have created fractures in the rock that emerged as channels for liquid water to flow. On the Primitive Earth. If asteroids like Ryugu’s father were able to retain not only hydrated minerals but also large amounts of water ice for more than a billion years, their potential to ‘water’ other planets is much greater than expected. Current models of the formation of terrestrial planets could be underestimating the amount of water contributed by these bodies. According to this study, Ryugu-like planetesimals could have entered two to three times more water into Earth than is commonly estimated. This would have direct implications on our understanding of the origin of the oceans, the atmosphere and in general the conditions that made it possible for us all to be living here. Images | NASA Hubble Space Telescope Carl Wang In Xataka | The last asteroid loaded with precious metals to graze the Earth escaped us. For the next one we already have a plan

We are clogging the ocean’s carbon toilet and it is something that is only going to cause us problems

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The ocean right now is acting as a big ‘carbon toilet’. An essential natural system that removes carbon dioxide from the atmosphere and locks him in the deep sea, helping regulate global climate. However, the recent heat waves we have experienced at sea are altering this critical process, which could have serious consequences for the climate of the entire planet. The ‘carbon toilet’. On the surface of the ocean we can now find organisms called phytoplanktonwhich have the ability to absorb CO₂ and produce oxygen through a simple photosynthesis mechanism with the help of sunlight. The problem is that we live in a life cycle that constantly advances, and that is why these organisms are food for small marine animals. called zooplanktonwhich generate feces in the form of small pellets that they sink to the seabed. This phenomenon, called the “biological carbon pump,” transports carbon from the atmosphere to the bottom of the sea, where it can remain isolated for centuries. In this way, the seabed can be seen as a large ‘cemetery’ of CO₂ stored in the feces of these animals. Something that in the long term is helping us clean the atmosphere and mitigate global warming. Heat waves. In the Pacific Northwest, two major episodes of marine heat waves that occurred in the periods 2013-2015 and 2019-2020 are changing everything. Temperature increases drastically altered the composition of phytoplankton and zooplankton, generating a “clogging” effect on the carbon toilet we have in the ocean. The lack of deep mixing and nutrients, caused by warming and stratification of the water, favored smaller species that produce feces that tend to float rather than sink, slowing the transport of carbon to the depths. A new layer. If the feces float, this simply means that the organic carbon now accumulates in the superficial layers of the water instead of reaching the deep areas where it was sequestered. This is also added to a greater bacterial proliferation in warm waters that decomposed more organic matter, releasing CO₂ again into the water and subsequently into the atmosphere itself. This is something that weakens the role of ‘buffer’ to try to compensate for the concentration of CO₂ in our atmosphere. Consequences. These changes not only affect the carbon cycle, but also the very base of the marine food chain. The decline in large phytoplankton reduces oxygen production and limits the feeding of larger marine species, including whales and commercial fish relevant to humanity. Zooplanktons are also responding to warming with changes in size and distribution, further impacting the efficiency of the carbon cycle since the smaller their size, the less CO2 they will capture and the less O2 they will produce. How it was done. In order to draw these conclusions, the research was based on a decade of data that was obtained through Argo biogeochemical floats. These are autonomous devices that have the ability to explore the ocean layers by measuring chemical and biological parameters without the need for constant human presence. This has allowed changes in marine ecosystems to be monitored in detail during extreme events, revealing hitherto invisible patterns and providing an essential tool for future studies and mitigation strategies. The future. These episodes of marine heat waves are increasingly frequent in our oceans due to global warming, as we are also experiencing in Spain. This means that if greenhouse gas emissions are not quickly reduced, the ocean could lose much of its ability to absorb atmospheric carbon. In Xataka | The question is not when it will stop raining, the question is how much more water will fall this fall

The oceans of the Earth were green for thousands of years. More and more scientists believe they will be again

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On February 14, 1990, 6,000 million kilometers from Earth, the Voyager 1 He took a photo. There, sustained in space by the mysterious forces of. Space-time, our planet is nothing more than a light blue motor between the sunlight reflected by the camera. Four years later, Carl Sagan baptized that photo as “that pale blue point.” What we just discovered is that it was not always the case. 3,000 million years ago, that point would have been green. Wasn’t it blue? Actually, according to Taro Matsuo and his team from the University of Nagoya in Japan explain in Japanduring most of the history of the earth its surface would not have been blue. For about 3,000 million years and until 600 million years ago (just when complex life begins on the planet) the predominant color seems to have been green. (No) take iron from the matter … The first is that, at that time, the indications tell us that the oceans were full of iron hydroxide. This inorganic compound absorbs blue light. In addition, naturally, water absorbs red light. That means that taking into account that chemical composition, the only free light was the green color. The other reason is the cyanobacteria. It’s about One of the first photosynthetic beings of history and not only used chlorophyll to absorb sunlight, but used fuses to absorb red and green light. The sum of these two things caused the seas to have a characteristic green color. And they had it for billions of years. It is true that it was not a pure green color. After all, blue is “a consequence of dispersion Rayleight of sunlight in the atmosphere. “So the color would tend to blue, but without a doubt it would be something much greener than current. What is the use of all this research? First, to understand that when The MIT explained in 2019that the sea will return green in the mid -century, we are talking about something very plausible. It is not just that A follow -up study In 2023 he confirmed that more than half of the land surface had gained greenery in recent years. It is that, for a long time, it was so. On the other hand, it allows us to answer one of the great questions of astrobiology: “Does only the blue tone of a planet serve as an indicator of its potential to house life?“And the answer, of course, is no: not a ‘non -radical’ is true; but one that reminds us that there are more things out there that can still dream our biology. Image | Georgetan#5 In Xataka | UFOs are a distraction: how astrobiology is our best asset to find extraterrestrial life

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