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‘Gold arrived on our planet as Earth was forming 4.5 billion years ago — it holds an extraordinary history'

Time of India

2 days ago

Science
Time of India

‘Gold arrived on our planet as Earth was forming 4.5 billion years ago — it holds an extraordinary history'

Jun Korenaga Jun Korenaga is Professor of Earth and Planetary Sciences at Yale University . He tells Srijana Mitra Das at TE about how gold got to Earth: It's a little surprising to connect to Jun Korenaga , not least because the scientist is sitting against the backdrop of a planetary surface that could be — but doesn't have to be — Mars. Speaking with purple rock and feathery clouds in a sunless sky behind him, Korenaga explains the origins of gold — and Earth. 'My work focuses on estimating early Earth's history. In the last few years, I've worked on the Hadean Eon which was about 4.5 billion years ago — this is the most mysterious part of our planet's history because we don't have a rock record for it. I work on the theoretical side and try to reconstruct what early Earth looked like.' Gold is part of early Earth's story, although in unexpected ways. A symbol of stability now, gold had quite a dramatic past. Supernovae or cataclysmic stellar explosions and star collisions occurred in the universe. The extreme pressure of such imploding stars was so high, subatomic protons and electrons got pushed into their core — these formed neutrons. Rapid neutron capture by iron then created heavy elements like uranium, lead, silver and gold. Interestingly, this process occurred very, very swiftly — and then, these elements were expelled into space. by Taboola by Taboola Sponsored Links Sponsored Links Promoted Links Promoted Links You May Like News For Jack Nicholson, 87, He Has Been Confirmed To Be... Reportingly Undo (Photos: Getty images) Thus, metals like gold and platinum arrived on Earth while our planet was still forming. Korenaga explains, 'About 4.5 billion years ago, Earth was hit by a Mars-sized rock and the moon formed as the debris from this collision went into an Earth-orbiting disk. More bombardment followed — there were plenty of leftover rocks orbiting the sun as well and several fell on young Earth. The landing of these objects is known as 'late accretion', comprising about the last 1% of planetary growth. In this period, some of the rocks which fell on Earth had metallic components like gold.' Importantly, gold and platinum are among highly siderophile elements (HSEs) — these are metals with an extremely strong affinity for iron. Korenaga smiles slightly and says, 'Now, if Earth was created with no funny twists in its story, we actually wouldn't have any gold on our planet's surface because, sticking to iron, this was heavy and should have gone straight down into the core which we cannot access. But we do have gold on the surface, which shows that part of Earth's mantle can retain metallic components.' Korenaga's research, conducted with Simone Marchi , posits the notion that there is a thin or 'transient' part of the mantle where shallow areas melt away and a deeper region stays solid. This part could hold falling metallic components and reach them to the mantle. In the simulations the scientists conducted, as a rock crashed onto Earth, it hit a localised liquid magma ocean where heavy metals sank to the bottom. As these reached the partially molten area underneath, the metal would start sinking further down — then, the molten mantle solidified, capturing the metal there. But how did this re-emerge to the part of Earth's surface humans could access? As Korenaga says, 'The part of the mantle which contains this metallic component is heavier and more chemically dense than the rest — to bring it up, you have to offset that density by being hotter than normal as hotter materials usually have lower density. Thus, thermal currents from Earth's core outweighed that compositional density and made these materials move up from the solid mantle to Earth's surface.' This process is called 'mantle convection', when hot mantle material rises as colder material sinks. Earth's mantle is almost totally solid — yet, over long geologic periods, it acts like a pliable material which can mix and move things within it. Those include the HSEs — like gold — which came to Earth from massive collisions billions of years ago and then reached the planet's surface through these enormous, yet intricate internal processes. Is gold found on other planets as well? Korenaga says, 'Gold is found on the moon — but its abundance there is much lower than on Earth. It is found on Mars too. Of course, we don't have direct samples from Mars but we have so-called Martian meteorites. These are found on Earth but because of their isotopic features, they are traced back to Mars. Analysing these rocks shows us the presence of highly siderophile elements there — again though, the abundance of these, like gold and platinum, is much lower than on Earth.' Do siderophiles contain a larger story of the formation of our solar system — and universe? Korenaga comments, 'We understand planetary formation in terms of silicate rocks and iron which makes up most of the core. Iron is a major element while silicate rocks are made of silicon, oxygen, magnesium, iron, etc. Highly siderophile elements exist in very small abundances — their presence by itself doesn't drive any major planetary formation processes but they stick with iron and by measuring such trace elements, we can study more details of planetary formation.' These abundances thus help us decipher the paths planets once took. The Golden Moon: This too has gold on it THE GOLDEN MOON: This too has gold on it Given its incredible history — arriving on Earth 4.5 billion years ago, seeping deep into its mantle, pushed to the top by extraordinary forces operating from within our planet — how should we think of gold the next time we see it? Korenaga replies, 'Gold is, of course, widely available as jewellery and other items from shops but when we look at it, we should actually think about its extraordinary origins — we shouldn't take gold for granted. Its presence helps us understand crucial details of the very existence of this metallic Earth and the formation of its unique atmosphere which is 78% nitrogen and 21% oxygen — why did our planet develop in this way? A simple everyday item like gold can hold big answers to that.' Korenaga concludes by remarking, 'Of course, my work explains why Earth's mantle has some amount of gold or platinum at the surface level but for humans to access pure gold, you need a concentrated form in a mine,' He adds, with a scientist's exactness, 'It is extremely inefficient otherwise to extract gold from rocks — but to understand the formation of gold mines, you need deeper knowledge about very local processes. And that is another story.'

'Space rainbow' captured by NASA's newest sun-studying spacecraft

Yahoo

23-05-2025

Science
Yahoo

'Space rainbow' captured by NASA's newest sun-studying spacecraft

The largest rainbowlike feature ever observed in the solar system was just captured by a newly launched spacecraft, as NASA scientists work to better understand the sun and forecast space weather. NASA's PUNCH mission, made up of four Earth-orbiting spacecraft, is focused on studying the sun's outer atmosphere, or corona. One of the first images from PUNCH, released earlier this month, appears to show a massive rainbowlike feature in the solar system. The rainbowlike feature in the image is very different from the rainbows most people are familiar with. On Earth, rainbows form when raindrops refract sunlight like a prism, creating an arc of colors across the sky. In space, this phenomenon was caused by sunlight reflecting off dust particles in the solar system-a glow known as zodiacal light. "The image is colorized to show the polarization (or angle) of the zodiacal light, a faint glow from dust orbiting the Sun. Hue indicates direction, and saturation indicates degree of polarization," NASA explained. "For example, a pastel green feature would be slightly polarized in the horizontal direction, while a deep blue feature would be strongly polarized in a diagonal direction." As mesmerizing as the image looks, it is the first step of the mission to study the sun. "These early images help the mission team confirm that PUNCH's cameras are in focus, working properly, and able to capture the quality observations needed to achieve the mission's goals." Once fully functional, PUNCH will help scientists monitor and predict space weather, including when the aurora could dance in the night sky.

Could the Sun Fry Earth with a Superflare?

Scientific American

02-05-2025

Science
Scientific American

Could the Sun Fry Earth with a Superflare?

In our daily lives, the sun seems constant and quiet, sedately shining at a steady pace. But looks can be deceiving: our star can also blast out powerful solar storms, huge explosions of energy and subatomic particles. If these are directed toward us, they can trigger auroras and disrupt our power grids, as well as play havoc with Earth-orbiting satellites. These storms are magnetic in nature. A fundamental rule in physics is that charged particles create magnetic fields around them as they move. And the sun is brimming with charged particles because its interior is so hot that atoms there are stripped of one or more electrons, forming what we call a plasma. The superhot plasma closer to the core rises, whereas cooler plasma near the surface sinks, creating towering columns of convecting material by the millions, each carrying its own magnetic field. These fields can become entangled near the surface, sometimes snapping—like a spring under too much strain—to release enormous amounts of energy in a single intense explosion at a small spot on the sun. This sudden flash of light accompanied by a colossal burst of subatomic particles is called a solar flare. The most powerful flare we've ever directly measured occurred in 2003, and it emitted about 7 × 10 25 joules of energy in the span of a few hours. That's roughly the amount of energy the whole sun emits in one fifth of a second, which may not sound very impressive—until you remember it comes from just a tiny, isolated region on the sun's surface! On supporting science journalism If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today. We also know that, historically, our star has spat out much bigger flares. High-speed subatomic particles raining down from solar storms slam into the nitrogen in our atmosphere to create an isotope called beryllium 10, or Be-10, which can be captured in polar ice after falling to Earth's surface. By examining ancient ice cores, scientists are able to obtain accurate dates for spikes in Be-10 (and other related isotopes), which can then be used to track historic solar activity. Such isotopic spikes have revealed what may be the most powerful solar eruption in relatively recent history, an event that occurred in 7176 B.C.E. Scientists argued at first about the cause of these spikes; the sun's activity didn't seem powerful enough to create the amounts of isotopes seen. Supernovae or gamma-ray bursts could explain the spikes, too—but only by occurring rather close to our planet, and that should've left behind other forms of evidence that, so far, scientists haven't found. Consequently, the current consensus is that the sun is indeed responsible for these massive upticks in isotopes. Scientists now call these spikes ' Miyake events,' in honor of Japanese cosmic-ray physicist Fusa Miyake, a leader in discovering and understanding them. While these flares were huge, there are reasons to suspect the sun is capable of unleashing even bigger ones. Some stars undergo what are called superflares, which are ridiculously powerful, reaching a total energy of 10 29 joules, or the equivalent of what the sun emits over the course of 20 minutes. In more human terms, that's about 300 million years' worth of our global civilization's current annual energy usage—all squeezed into a brief burst of stellar activity. Superflares are relatively rare. Observing them in any given star would take a stroke of luck—unless you stack the odds in your favor. That's just what an international team of astronomers did. The Kepler spacecraft monitored about half a million stars over a period of a decade, looking for telltale signs of accompanying planets. But all those data can be used for other things, too. The astronomers looked for superflares arising from more than 56,000 sunlike stars in Kepler's observations—which added up to a remarkable 220,000 total observed years of stellar activity. The researchers published the results in Science in late 2024. By sifting through that vast dataset, the team found 2,889 likely superflares on 2,527 sunlike stars. That works out to roughly one superflare per sunlike star per century, which seems pretty terrifying because it would presumably mean the sun sends out an explosive superflare every hundred years or so. But let's not be so hasty. For one thing, a star's rotation can powerfully influence the development of flare-spewing magnetic fields, and the rotational period was unknown for 40,000 of the study's examined stars—so it's possible this part of the sample isn't representative of the actual sun. And 30 percent of the superflare-producing stars were in binary systems with a stellar companion, which could also affect the results. The list of potential confounding variables doesn't stop here—there are several other factors that might make a seemingly sunlike star more prone to producing superflares than our own sun is. Then again, as I already mentioned, Be-10 and other telltale isotopes can be produced in other ways that don't involve stellar flares. And, for that matter, it's not at all clear how well superflares would specifically make such particles. So although we've counted five sun-attributed Be-10 spikes across the last 10,000 years, that doesn't mean the sun has only produced that many strong flares in that time. Perhaps there were others that left more subtle, as-yet-unidentified records in the ice—or that weren't aimed at Earth and therefore produced no terrestrial isotopic signal at all. If the sun did blow off a superflare today, what would be the effects? The impacts to life on Earth would probably be pretty minimal; our planet's magnetic field acts as a shield against incoming subatomic particles, and our atmosphere would absorb most of the associated high-energy electromagnetic radiation (such as gamma and x-rays). Our technological civilization is another matter, though. A huge flare could fry the electronics on all but the most protected satellites and disrupt power grids to cause widespread and long-lasting blackouts. Engineers have devised safeguards to prevent damaging electrical surges from most instances of extreme space weather, but if a flare is powerful enough, there may not be much we could do to avoid severe damage. Should we worry? The takeaway from the study is that it's possible the sun produces superflares more often than we previously thought, but this conclusion is not conclusive. So consider this research a good start—and a good argument for getting more and better information. Don't panic just yet!

China's daytime laser ranging breakthrough takes moon race to new heights

South China Morning Post

30-04-2025

Science
South China Morning Post

China's daytime laser ranging breakthrough takes moon race to new heights

China's Tiandu-1 satellite has taken part in a laser ranging experiment in Earth-moon space under strong daylight conditions, which the satellite's developer says is the first test of its kind. Advertisement China's Deep Space Exploration Laboratory (DSEL) ran a laser ranging experiment on April 26-27 from the Earth to the Tiandu-1 experimental satellite, which has been orbiting the moon since its launch in March last year, according to state broadcaster CCTV. Satellite laser ranging measures the distance to orbiting satellites, which involves a laser at an observatory sending pulses of light to the satellite which then bounce back, allowing for distance to be calculated. While satellite laser ranging tracks Earth-orbiting satellites during the day, conducting these experiments in Earth-moon space has previously been limited to nighttime, as strong daylight can interfere with the laser signal and cause signals to be lost in background noise. This allows limited observation windows and data collection for satellites in Earth-moon and lunar orbit, which are vital to China's push for expanding its presence on the moon. The test, which DSEL told state media was the world's first Earth-moon laser ranging test under strong daylight conditions, expands the limits of the technology and will help with carrying out future deep space missions. Advertisement The Tiandu-1 satellite was launched into space alongside the Tiandu-2 and Queqiao-2 relay satellites in March last year. The mission was intended to help verify new technologies in the construction of an Earth-moon communication and navigation system.