Antarctica’s gravity hole is getting stronger

 Scientists reveal that Antarctica’s gravity hole is growing stronger

Although Earth is approximately spherical, its gravity field doesn't adhere to the same geometry. In visualizations, it more closely resembles a potato, with bumps and divots. For decades, scientists have been studying intriguing “gravity holes,” which are enormous depressions in the Earth’s crust where the effects of gravity are significantly lower than average. One of the strongest of these depressions, where the gravity field is weaker, lies under Antarctica. Now, new models of how the so-called Antarctic Geoid Low evolved over time have shown that it's only getting stronger, driven by the long, slow movement of rock deep below Earth's surface, like a giant shifting in its sleep. "If we can better understand how Earth's interior shapes gravity and sea levels, we gain insight into factors that may matter for the growth and stability of large ice sheets," says geophysicist Alessandro Forte of the University of Florida. It’s an especially pertinent phenomenon in the Antarctic, a region which has seen significant changes not just due to global warming, but far longer-term climate changes spanning tens of millions of years, long before the emergence of humans and their environmentally disastrous footprint on the planet. The effects of gravity are particularly weak beneath the icy continent when accounting for our planet’s rotation, the result of slow rock movements deep beneath the ice.

Earth's geoid, the bumpy potato shape of the gravitational field, is uneven because gravity is linked to mass, and the mass distribution inside the planet is uneven, due to different rock compositions having different densities. It's not a huge difference that you'd notice at the surface. Maps tend to exaggerate it so we can see what's going on; if you weighed yourself at a geoid low and a geoid high, the difference would be just a few grams. Nevertheless, the geoid represents a window into processes deep inside Earth that we can't observe directly. University of Florida geophysics professor Alessandro Forte and Paris Institute of Earth Physics researcher Petar Glišović found that these rock movements are correlated to major changes in Antarctica’s climate, suggesting how the area’s gravity shifts may have allowed its ice sheets to grow. The pair created a detailed map of the Antarctic’s “gravity hole” to study how it changed over millions of years, using a wealth of global earthquake recordings from across the planet. “Imagine doing a CT scan of the whole Earth, but we don’t have X-rays like we do in a medical office,” said Forte. “We have earthquakes. Earthquake waves provide the ‘light’ that illuminates the interior of the planet.”

Forte and his colleague, generated a detailed map of the Antarctic Geoid Low using another window into Earth's interior: earthquakes. Seismic waves from earthquakes travel through the planet, changing speed and direction as they encounter materials with different compositions and densities. Using the earthquake data, the researchers constructed a 3D density model of Earth's mantle and extrapolated it into a new map of the entire planetary geoid. They compared this map with the gold-standard gravity data collected by satellites and found it to be a close match. This was the easy part. The next step was to try to turn back the clock to assess how the geoid has evolved since the early Cenozoic. Using computer models, the team reconstructed the state of Antarctic’s gravity hole 70 million years ago, when dinosaurs still roamed the Earth. They determined that the hole has gained strength over tens of millions of years, coinciding with major changes in the continent’s climate system and the widespread formation of glaciers, which in turn, had sweeping effects on sea levels the acidity of our planet’s oceans. While the findings aren’t a definitive causal link between the two, rock movements and shifting gravity causing ice to grow, Forte and Glišović are hoping to test whether sea level changes may be directly influenced by this strengthening gravity hole.

Forte and Glišović fed their map into a physics-based model of Earth's mantle convection, rewinding Earth's interior geological activity to see how the geoid evolved over that timeframe. Then, from their starting point, they let the model run forward to see if it could reproduce the geoid we see today. They also checked whether their model reproduced real changes in Earth's rotational axis known as True Polar Wander. It arrived at the current geoid and matched the polar wander, suggesting it also provides an accurate representation of the geoid's evolution. “How does our climate connect to what’s going on inside our planet?” Forte asked rhetorically in the statement. “If we can better understand how Earth’s interior shapes gravity and sea levels, we gain insight into factors that may matter for the growth and stability of large ice sheets.” The results showed that the Antarctic Geoid Low is not a new development; a gravitational depression has been sitting near Antarctica since ages. But it hasn't remained static. About 50 million years ago, its position and strength started to change dramatically, timing that matches a sharp bend in the polar wander.

According to the model, the anomaly formed as tectonic slabs sub ducted beneath Antarctica and sank deep into the mantle, altering the planet's gravity field at the surface. Meanwhile, a broad region of hot, buoyant material rose upward, becoming more influential over the past 40 million years and strengthening the geoid low. Interestingly, this may be linked to the glaciation of Antarctica, which began in earnest around 34 million years ago. It's only a speculative link, but here's the interesting thing about the geoid: it shapes sea level. So, as the geoid shifted downward around Antarctica, the local sea surface would have lowered with it, potentially influencing the growth of the ice sheet. That's obviously a hypothesis which requires further testing. However, the work does show that different geodynamic processes, from mantle convection to the geoid to the motion of the poles, can all be connected and influence each other. The gravity hole under Antarctica may be subtle, but it is a reminder that even the slowest processes deep inside Earth can leave a lasting impression on the world above for us.

Muhammad (Peace be upon him) Name

 

ALLAH Names

 

Discovery of a new planet named Enaiposha

New Kind of Planet named Enaiposha unlike anything discovered in our solar system

An object we thought belonged to the most common category of planet in the galaxy has turned out to be something we've never seen before. The exoplanet Enaiposha, or GJ 1214 b, is a hazy world orbiting a red dwarf star about 47 light-years from Earth. Previously likened to a mini-Neptune, in-depth observations obtained using JWST now suggest the exoplanet is more like Venus, only much larger. This would make it the first known of its kind, a category astronomers are calling 'Super-Venus'. It started as another exoplanet in a group labeled “ordinary.” No one expected that a world, once thought to be a mini-Neptune, would reveal traits of a super-Venus and change how we see certain planetary types. Astronomers used JWST data to learn more about an unusual place called Enaiposha, which orbits a red dwarf star. Enaiposha is one of the most studied exoplanets in the sky. It was discovered in 2009, with a mass and radius that put it somewhere between Earth and Neptune. Subsequent observations revealed a substantial atmosphere.

Enaiposha, that also goes by the identifier GJ 1214 b, was first placed in a category that normally describes small, gas-rich worlds. New observations, however, suggest that it is more like Venus but on a bigger scale. Researchers propose calling it a super-venus because it appears to have a thick atmosphere composed of hydrogen, helium, water, methane and CO2. This finding came from recent measurements which showed faint traces of molecules at key parts of the spectrum. Exoplanets in this mass regime generally fall into one of two categories. The Super-Earths are thought to be terrestrial exoplanets larger than Earth, hosting hydrogen-rich atmospheres, if they have one at all. When Enaiposha crossed between its star and Earth, tiny dips occurred at points on the spectrograph where certain gases absorb starlight. The data hinted at a metal-rich atmosphere with less hydrogen floating around than scientists had expected. One portion of the team’s work pointed that water vapor was present in the atmosphere, but that alone was not the big story. Small signs of complex metals emerged, which is odd for a planet once categorized in a simpler way. Furthermore, as starlight passed through Enaiposha’s outer layers (atmosphere), certain wavelengths of light were also absorbed which indicated the signatures of CO2 and methane.

So-called mini-Neptunes can be of a similar size, but their composition is significantly different, with denser atmospheres rich in hydrogen and helium, and liquid oceans possibly wrapping their surfaces. Mini-Neptunes are the most numerous of the more than 5,800 confirmed exoplanets at time of writing, which is interesting, because we have nothing directly analogous to them here in our Solar System. Research on Enaiposha, a super-Venus, is still tough because of the haze. Observations pick up only subtle signals from deeper parts of its atmosphere. A single measurement can be overwhelmed by the star’s brightness. Multiple follow-up sessions and new instruments may be needed to confirm all of these ingredients. The study was led by astronomers Everett Schlawin from the University of Arizona and Kazumasa Ohno from the National Astronomical Observatory of Japan (NAOJ). The scientists got a faint clue that CO2 may exist in concentrations akin to those found on Venus. They saw how light changed as it went through Enaiposha’s thick skies. “The detected CO2 signal from the first study is tiny, and so it required careful statistical analysis to ensure that it is real,” noted Ohno, the team member leading the theoretical investigations. Experts sometimes place planets slightly bigger than Earth in the super-earth bracket. Those even larger but still under Neptune’s mass sit in the mini-Neptune group. This planet seems to occupy a weird middle zone. The findings have driven some scientists to propose that Enaiposha represents a new sub-type of exoplanet, or at least a neat twist on the usual groupings.

Both super-Earths and mini-Neptunes are intriguing to scientists because, if other conditions are just right, they might be habitable to life as we know it. This is partly why astronomers closely study Enaiposha, a world clocking in at 2.7 times the radius and 8.2 times the mass of Earth. Although the world is far too close to its host star, Orkaria, and therefore far too hot to be likely habitable itself, it's proximity to Earth means we can see it relatively easily, meaning it could give us information which might aid in our understanding other similar exoplanets elsewhere in the galaxy. But Enaiposha poses some problems, too. Its atmosphere is so thick that we can't peer into it very easily. But based on JWST and Hubble observations, the exoplanet may have a water-rich atmosphere which also contains vaporized metals. Sub-Neptune planets that are smaller than Neptune in size are the most common type of planet known to exist in the Milky Way, but they are absent from the solar system. They have atmospheres which consist of a variety of gases and atmospheric spectroscopy is used to analyze what gases are present. Enaiposha differs from a typical sub-neptune in that its upper layers are blanketed by haze and aerosols. This makes it very difficult to analyze the atmosphere spectroscopically to establish which gases form the atmosphere on the exoplanet. Venus also has clouds that block most views of its surface, but Enaiposha takes this phenomenon further. It is bigger, hotter and enveloped by layers which make it especially hard to examine.

New research efforts suggest that we may have missed something. a team of researchers has studied transit data for Enaiposha, and discovered something unexpected. As the exoplanet passed in front of the star, whipping around on its 1.6-day orbit, JWST data suggests that starlight traveling through Enapoisha's atmosphere was altered by CO2, in concentrations similar to the CO2 which makes up more than 96% of the atmosphere of Venus. But the signal was very faint. "The detected CO2 signal from the first study is tiny, and so it required careful statistical analysis to ensure that it is real," Ohno says. "At the same time, we needed the physical and chemical insights to extract the true nature of GJ 1214 b's atmosphere." Some wonder whether similar planets hide in other star systems. It may be risky to assume that everything beyond our Sun fits neatly into known knowledge. Astronomers have found thousands of strange worlds. This one stands out for defying what was presumed normal in the mini-Neptune category of exoplanets. One encouraging aspect is how these methods might apply to places that could harbor life. Enaiposha is scorching, so it is not a promising location for habitability. So, the researchers set about conducting theoretical models which could explain the data. The scenario that best fit the observations, they found, is if Enaiposha has an atmosphere dominated by metals at lower altitudes, and only relatively small amounts of hydrogen. Still, the process of analyzing its hazes and thick skies could help scientists interpret atmospheres around other exoplanets in less extreme locations. This matters for anyone seeking to detect breathable air anywhere beyond our own system.

At higher altitudes, the atmosphere consists of a haze dense with aerosols, as well as the CO2 their reading implied. From this emerges the notion of the super-Venus, a world similar to Venus: very hot, and choked by a carbon-rich atmosphere through which it is difficult to see. But the exoplanet's trickiness has not yet been circumvented. The observed signature is so small that extensive follow-up will be required to determine if the team's conclusions are correct, especially because it's something new. "We stress the importance of high precision follow-up observations to confirm the metal-dominated atmosphere," the researchers write, "as it challenges the conventional understanding of interior structure and evolution of sub-Neptunes." Some want to see whether metals in Enaiposha’s air, as a super-Venus, can form droplets or complex clouds. This might explain why so little light passes through its atmosphere. Others suspect it could be a stepping stone for modeling how thick atmospheres evolve. It might also show that sub-Neptunes can morph into something else with time. In future, further modeling of the planet’s atmosphere, interior structure and origins will provide valuable insights about how sub-Neptunes like GJ 1214 b form and evolve in our universe.

Muhammad (Peace be upon him) Name