Sunday , May 22 2022

How they discovered a crater in Greenland caused by an asteroid – Science – Life


An exploration of ice in Greenland has revealed evidence suggesting the impact of a single asteroid an entire kilometer of the island just 12,000 years ago.The Crter, created by a crash of 30 kilometers, has so far remained hidden under an 800-meter-thick layer of ice.

Recently, it was exposed to the ultra-wideband radar system developed by the Center for Remote Ice Detection (CReSIS), from the University of Kansas (KU) in the United States. Characteristics of the crater, the result of the Hiavath catastrophe in the remote northwest of Greenland, are described in detail in an article published in Science Advances.

It is identified with data collected between 1997 and 2014 by CO for Nasa's program for regional climate assessment and IceBridge operation, and supplemented with more data collected in May 2016 using a coherent multipurpose radar probe. depth (MCoRDS) developed in the KU.

"We have accumulated a large amount of data on radar explorations over the past two decades, and glaciologists have gathered this information to get a map of what Greenland is under ice," says co-author John Paden, associate professor of electrical engineering and science. Calculation at KU and scientific associate in CReSIS.

"Danish researchers watched the map and saw this great depression, a similar crater, under the iceberg and the observed satellite images, Since the crater is on the edge of the ice sheet, a circular pattern can also be seen there. Based on this discovery, in May 2016, a detailed radar study was carried out using a new state-of-the-art radar designed and built by the KU for the Alfred Vegener Institute in Germany, "he adds.

Paden, who helped in the development of radar signal processing software MCoRDS, participated in low-water flights in the structure of the network through a crater impact to detail his dimensions.

"You can see a hardened construction on the edge of the ice sheet, especially when you fly high enough," he says. In most cases, the crater can not be seen through the window of the plane. Using satellite images at a low angle of the sun that highlights the hills and valleys in the ice sheet, you can really see the circle of the entire crater for these images. "

In order to confirm satellites and radar findings, the research team conducted further field studies on the glaciophluvial sediment of a larger river that dried the crater. The work showed the presence of "impact of quartz and other grains related to impact", such as glass. The research team believes that these walls and glass beads will be produced from the impact of grain fusion in the metadimensional mother wall.

Determine the date of impact

The work continues to determine more precisely the moment of the impact of the asteroid in Greenland. The authors say it there is evidence that suggests that the red cross of Hijavath was created during the Pleistocene, since this age is more consistent with the conclusions of the currently available data. However, even this wide range in time remains "unsure." Southwest of the crater, the team found an area rich with potential residuals emanating from impact, which could help reduce the date range.

"There would be damages in an atmosphere that would affect the climate and the potential to soar a lot of ice, so there could be a sudden flow of fresh water at the Nares Pass, between Canada and Greenland, which would affect the ocean's flow in the region's entire" , claims Paden. Evidence suggests that the impact probably occurred after the Greenland ice sheet was formed, but the research team continues to work on a precise date. "

According to planetary geologist David Tovar, the discovery of the crater in Greenland shows that there are several regions of the planet that can still preserve evidence of craters. "Many times geologists do not take into account these structures due to lack of knowledge about their training processes and the type of material that affect asteroids on different types of rock," says the expert. .

"Similarly," he continued, "it's obvious that a job that matches the acquisition of remote sensor data (satellite images, aerial photography, geophysics) is of great help when you want to examine the structure of the impacts that are covered by some material, in this particular case, ice. "

The item points out that this work should be supplemented by field visits where scientists with knowledge in planetary geology should collect evidence in hand samples, "That is, wall samples with typical structures produced by the impacts, which will be analyzed later in the laboratory, with the final aim of amalgamating key evidence on different scales: mega, macro and microscopic. A job that has been going on for years and should not be done lightly."


Source link