Last November, the scientists' mind was inflated by the discovery of a 19-mile crater in Greenland. The crater hides only 150 km from the main air base. Scientists studying aircraft with the NASA IceBridge operation found that they had tested their equipment before they collected Arctic data. On Monday, the same group announced that they had found another possible impact crater, which is even bigger, and it sits just over 100 miles from the first one.
This time they searched.
NASA scientist Joe MacGregor was on a team that found the first crater under the Hiawatha glacier in north-west Greenland. He says that after Hiawatha's results, he doubted that there might be more craters on the ice sheet. It took only a couple of hours to scan the map of Greenland until it discovered a suspiciously round geological function alongside the newly discovered Hiawatha Crater.
Under the Ice
Ice sheets for the landscape are quite rough. They are the reason why the US Midwest is so flat – everything becomes glacier. That is why scientists have long believed that geological features, such as craters, even if they ever existed, would eventually level out if they were under ice.
MacGregor, glaciologist and scientist at NASA's IceBridge project explains that he noticed a new crater a few years ago on the Greenland landscape under the topographic map of NASA
"When you look at that map, you can see depression in northwest Greenland – it's not Hiawatha (crater) ”, Explains MacGregor. He says he consulted several other maps, and "it was quite clear that the surface of this depression was circular. And it was quite interesting. I was ascended from my desk and went to the hallway, getting into myself, like, what, another crater?
Then the hard work came, says MacGregor. Impact craters, unlike other round holes on earth, say, from old failed volcanoes, often cause specific anomalies in magnetic and gravitational fields. Comfortable scientists have already conducted geophysical research in this area, which means that they already have the data needed to explore a potential crater.
Volcanic remains and impact craters leave a variety of geophysical signatures on the landscape – magnetic and gravity anomaly fields. The latter is associated with post-exposure penetration of the Earth's crust, becoming less dense than before. And in this case, the crater signature signifies that it is really a crash crater
Ice, Ice, Baby
It is premature to present a real date on this crater, but there are some initial clues. Ice cream at the crater is at least 79,000 years old, but it can mean a lot of things – for example, ice on the crater can now be moved away from the home for millennia.
Ice is a MacGregor specialty. “We can really say that the ice layer on the second crater is very different from what we saw at Hiawatha. Hiawatha layering was what prompted us to suspect youth. In the second potential crater, layering is fairly old and smooth without clear inconsistencies; it looks like a good part of Greenland. So it can only be suspected that it is probably older, ”he says.
Another hint of the great age is its depth – the crater is quite shallow, with such a wide diameter that covers 22.7 miles. Scientists have calculated that the impact of a crater of this size would also create almost half a mile deep crater, which means that the structure is slightly worn out. It is about doubling as a neighbor of Hiawatha. Based on the expectation of a worn ice sheet on the crater, and how fast, the age of a young crater can be more like one hundred thousand to one hundred million years.
What are the chances, though
If you read this thinking, "what is odds," do not worry that scientists have also been seriously hindered. If both structures are officially approved as impact craters and they are confirmed to be of different ages, as evidenced by the initial evidence … what is the probability that two unrelated effects will occur only 100 miles apart?
scientists, so they actually calculated the odds
Only last month, Sara Mazrouei of the University of Toronto and colleagues published Science updated estimates of land impact based on both known data Cragers and Crater faced neighbors, Moon.
MacGregor and his team used these calculations to calculate the probability that two unrelated craters would ever happen. Considering the size of the rifles needed to produce such a crater, the size of the Earth and the usual size of the Earth's surface, they estimate that an unrelated pair of large craters should stand around every seven billion years. In other words, not very likely.
But they also looked at another way, though – to reflect the "birthday paradox". The birthday paradox relates to the odds that two people have on their birthday; mathematically, more often than you think. In any random group of 23 people, the chance of two getting a birthday is about 50/50. In the 70's this is almost 99.9 percent.
So how many craters should be sprayed on Earth until two of them are next to each other without giving birth? The team used Mazrouei's assessments again: over the last 650 million years, there were probably about 355 impacts, although only about 10 percent of the Earth's surface is stable enough to have such craters today. The team tried a simulation that randomly distributed 355 meteors across the planet and found that there would be an average of 13 crater pairs in history, unrelated but close to each other. Cut it up to 10 percent. Craters that survived until today, and you have one, perhaps two, crater pairs
Two such crater pairs have already been discovered: one in Quebec and one in Ukraine. But this does not mean that the third pair is out of bounds – sometimes three coins open up all the heads, even when you expect at least one "tail".
. Skeptics are expected to
"And Hiawatha, and this second potential crater falls into an unusual category of impact craters," says MacGregor. "They are on the ground, but they are ice, so they are relatively hard to try in all the ways you want."
To really confirm the crater as an impact crater, MacGregor explains that the impact on the geological community will be much more than an abnormality of gravity. But the information they need is beyond the mile of ice
"Maybe another way to think about it takes about 10 seconds to convince a planetary scientist that this is an impact craters," jokes MacGregor, "but it's" It will probably take 10 years to convince geologists of land impact. "
MacGregor says it is about a working expedition that would be needed to explore craters, but there are no solid plans yet. He is not currently interrupting his day job with IceBridge, despite his new recordings of craters.
"It's great fun, but I will remain a glaciologist," says MacGregor. "I hope for a lot of good reasons, we still want to know a lot more about what ice will do in the future."