Gravitational anomaly and evidence of meteor impact
In the years 1958-1960 in this area carried outcomplex geological research French and American expeditions, which discovered some anomalies of gravity here. The area of anomalies was outlined, which had the shape of a circle with a diameter of about 240 km. It was later found that this gravitational anomaly is very similar to those observed near large meteorite craters. Then the first assumption was made that the anomaly was formed by the fall of a huge meteorite.
The so-called "gravitational anomaly of the EarthWilkes' was first discovered in 2006 when NASA satellites noticed gravitational changes indicating the presence of a huge object in the center of a 300-mile-wide impact crater.
Image of land height in East Antarctica,received by radar. Higher elevations are displayed in red, magenta, and white; the location of the Wilkes Land crater is circled (above the center). Image courtesy of Ohio State University. The Chicxulub crater inset is included for comparison.
(Image: Ohio State University
In 2002, two twin satellites of NASA and the German Center for Aviation and Cosmonautics were launched from the Plesetsk cosmodrome under the GRACE program (eng. Gravity Recovery and Climate Experiment), which were supposed to study the gravitationalfield of the earth. In 2006, a group of researchers led by Ralph von Frese and Laramie Potts analyzed in detail the Earth's gravitational field measurements obtained from the GRACE satellites, and confirmed the scientists' assumption made in the 1960s that this the area of the giant astrobleme. According to updated data, its diameter is 480 km.
Astroblem - Impact crater - depression,appearing on the surface of a celestial body when a smaller body falls. A large impact crater on the Earth's surface is called an astrobleme. The event itself is sometimes called an impact or impact event. About 150 astroblems have been discovered on Earth.
The gravity recovery experiment andClimate (GRACE) was a joint NASA / German Aerospace Center mission that ran from March 2002 to October 2017. By measuring gravity anomalies, GRACE showed how mass is distributed over the planet and how it changes over time.
New details of 2018 about the gravitational fieldEast Antarctica, obtained by the Gravity Recovery and Climate Experiment (GRACE) mission, revealed a noticeable positive gravity anomaly in the open air over a buried basin with a diameter of approximately 500 kilometers centered in Antarctica in the northern part of Wilkes Land.
Comparison of the sizes of large craters in the solar system. Wilkes Land Crater is third from the left. Image courtesy of Ohio State University.
An unusual combination of geological andgeophysical anomalies on Wilkes Land in Antarctica makes it clear that these features may be due to their origin to a super-fast impact of an extraterrestrial body.
Here are some of these obvious pieces of evidence:
- Negative gravitational anomaly (unusual, deviating from the regular manifestation of the gravitational field of an object)
- Visible structural deformation: basin profiles in the ice sheet and subglacial topography,
- The presence of a border, structures similar to the edges of terrestrial, lunar, Martian and Mercury impact craters,
- Correspondence between morphological dimensions andthe dimensions and dimensions of terrestrial, lunar, Martian and Mercurian impact craters, namely, crater rim width, crater rim height, crater depth, and crater diameters.
NASA satellite detects "gravitational anomaly"300 miles wide under the ice of Antarctica, corresponding to the impact of a giant asteroid and volcanic streams of Siberian traps that lasted for about two million years and covered the Permian-Triassic mass extinction that occurred from 251 to 250 million years ago. The impact crater is estimated to be nearly three times the size of the dinosaur-era end-era Chicxulub crater (pictured above) and presumably formed before the Cretaceous formation on the east coast of Antarctica.
Some researchers believe that the anomalycould have been the remnants of a giant asteroid much larger than an asteroid that could have killed the dinosaurs. They are sure that it was this asteroid that caused the Permian-Triassic extinction (informally in English it is called the “Great Extinction”), which killed 96% of the Earth's sea creatures and up to 70% of terrestrial organisms.
This Wilkes Land hit is much more than a hit,that killed the dinosaurs, and probably would have caused catastrophic damage at the time. All the environmental changes that could result from exposure would create a very corrosive environment that was really difficult to endure. So it is logical that a lot of life died out at that time.
Ralph von Frese, was a professor of geological sciences at Ohio State University when he discovered the crater.
However, later, Chinese scientists found evidencethe fact that the Permian extinction, the largest catastrophe in the history of the Earth, occurred in "moments" by geological standards, in a matter of thousands of years. Their findings were presented in the GSA Bulletin magazine.
There is evidence that at this time inlarge quantities of carbon dioxide and methane were released into the atmosphere and oceans, dramatically changing the climate and making the Earth extremely hot and arid. As studies by Russian geologists show, these emissions came to the surface of the planet in Eastern Siberia, in the vicinity of the Putorana and Norilsk plateaus, where about 252 million years ago powerful magma eruptions occurred.
Most scientists today are confident that these outpourings of lava were implicated in the extinction of animals, but the exact mechanism of their action on the climate and ecosystems of the Earth remains a matter of controversy.
What scientists have found under a layer of ice
Scientists have used gravity fluctuations,measured by NASA's GRACE satellites to peer beneath the icy surface of Antarctica, and discovered a 320 km wide plug of mantle material — mass concentration, or "mascon" in geological parlance.
Mascons are the planetary equivalent of a bump on the head. They form where large objects crash into the planet's surface. On impact, the denser layer of the mantle bounces off the overlying crust, which holds it in place under the crater.
This is the region of the lithosphere of the planet or naturalsatellite causing positive gravity anomalies. The most famous are lunar mascons, which were discovered and localized by disturbances in the motions of artificial satellites of the Moon. Most often, mascons are located under the lunar seas, which have a rounded shape.
When scientists imposed their gravitationalimage on aerial radar images of the ground under the ice, they found the mascon perfectly centered within a circular ridge about 482 km wide - a crater large enough to hold Ohio.
The design of the ridge alone proves nothing. But for scientists, the addition of a mascon adds to his theory of a meteor impact.
If I saw the same masked signal onMoon, I would expect to see a crater around it. There are at least 20 impact craters of this size or larger on the Moon, so it is not surprising that they are found here. The active geology of the Earth has probably cleared its surface of many others.
Ralph von Frese
However, later, scientists recognized that such "signals"open to interpretation. Even with the help of radar and gravimetric measurements, scientists are just beginning to understand what is happening inside the planet. However, von Frese said that the circumstances of the radar and mask signals confirm their interpretation.
To estimate when the collision occurred, the scientists took a clue from the fact that the mascon is still visible.
On the moon, we can see craters and observemascons. The catch is that it is almost impossible to find mascons on Earth, because the planet is geologically active. The interior is eventually rebuilt and the mascons disappear. As an example, scientists cite the Vredefort crater in South Africa, which must have once had a mascon, but now no evidence is visible.
Based on what scientists know aboutIn the geological history of the region, Wilkes Land's mascon was formed recently by geological standards - probably about 250 million years ago. In half a billion years, the Wilkes Land mascon will probably also disappear, Ralph von Frese is sure.
What's the bottom line?
Some scientists are sure that an M-class asteroid is hidden in the bowels of Antarctica in the Wilkes Land area, that is, consisting mainly of metals. It is he who can change our understanding of life in space.
However, there is currently no way to check thishypothesis. The cost of the expedition and the drilling of ice of this thickness is enormous. The crater is located under the Antarctic ice sheet, so direct observations are not possible. However, even the ultimate existence of a giant impact crater, twice the size of Chicxulub crater on the Yucatan Peninsula, of extraterrestrial origin, 1.6 km beneath Wilkes Land in East Antarctica, remains controversial. Despite a lot of research, Wilkes Land remains the most unexplored and most attractive territory for scientists.
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