By comparing the age of impact craters on the moon to those on Earth, researchers say they have discovered a surge in the rate of asteroid strikes starting around 290 million years ago – a finding that runs contrary to scientific convention. And indeed, not everyone is convinced by the evidence.
Scientists who teach ancient impact craters on earth have a problem: erosion. Veterinary, volcanic, tectonic and other geological processes have swept away the traces of our planet's oldest impact craters, making it difficult to chronicle the history of asteroid impacts on Earth.
New research published today in science suggests the moon, with its extensive collection of impact craters, can help.
Like neighbors, the Earth and Moon have experienced similar asteroid strikes over the solar system's history. But the moon, unlike ground, is not subject to the same erosion processes. Therefore, the Moon's surface has retained its long-term record of its impact history. If the lunar craters can be dated, record historical bombardment rates on Earth.
With a new technique of data-lunar craters from a distance, a research team led by Sara Mazowie from the Department of Earth Sciences at the University of Toronto is able to do just that. The technique allowed them to date more than 10 kilometers (6 miles) and younger than 1 billion years, with lunar craters with diameters.
This exercise has two important findings, both of which draw on conventional ideas from Earth's impact record.
The first is that the impact rate on Earth has increased by a factor of 2.6, or between two and three times, about 290 million years ago, at the end of Paleozoic Era and just a few before the appearance of dinosaurs. The second major finding, in the words of the researcher, is the "almost complete absence of terrestrial craters older than 650 million years."
According to researchers, the point suggests a "massive global-scale erosion event around that time." The event they are talking about is the Theorized Snowball Earth – a time when most if not all of our planet was coated in ice.
The idea that the frequency of moon and earth impacts has jumped since 290 million years ago is against conventional thinking. Theoretically, the rate of asteroid strikes should be decreasing – and not – as the debris gradually dissipates from the formation of the solar system. The authors of the new study claim a great demand – one that requires excellent words.
Indeed, some of the experts we talked to were not entirely convinced of the new paper, so it was too many assumptions that these methods are not persuaded enough, and more evidence is needed to reverse these claims.
To date, the lunar craters, Mazrolia's team used thermal data and images collected by NASA's Lunar Reconnaissance Orbiter (LRO). A device on the lorry, called the diviner, provided this data by measuring the heat radiation of the moon's surface. At night, big rocks give away more heat than fine soil, allowing the diviner to do their job. And so it happens that young craters on the moon are surrounded by large rocks.
"When a crater is formed after an impact, it excavates a lot of rocks," Maazroy explained. Gizmodo. "The rocks around the crater eventually turn into regolith, or lunar sand, due to micrometeorite bombardments. This process takes about 1 billion years. As craters grow older, they become less rocky. We used the relationship to get older for lunar craters. "
With this technique, researchers are able to collect the ages of all Lunar Craters younger than around a billion years – a complete time-consuming process, to be sure.
"It was a few months to map all the young lunar craters. But, I started this project when I started my PhD five years ago," said Mazroy. "We have to check our data and methods to make sure they are healthy. After about two years, when we started to compare lunar craters to terrestrial, we saw some very interesting results. We had to ensure and prove to multiple reviewers, when We presented our paper that we have accounted for all terrestrial craters on the ground. "
As said, Mazrouli and her colleagues correlated the age of lunar impact craters with those on Earth. The common belief among scientists is that many earth-craters have been wiped out by geological processes, but comparing the lunar craters to earthly ones, Mazrouli and her colleagues showed that, for their great craters – more than 20 km in diameter and younger than 650 million Years – A complete record of terrestrial impact crusters does indeed exist. To be clear, however, this only applied to craters found on stable terrain, excluding areas like the ocean, the Amazon, and so on.
Analysis of this data exposed the frequency of spike in impact starting around 290 million years ago, but yielded other interesting findings.
By re-assessing the terrestrial impact record, researchers discovered the death of craters on earth between 300 million and 650 million years ago during the pre-firecrack. The surprising deficit of craters, according to the study, is not the result of erosion, but rather an unexpected decline in asteroid impacts during the historic period.
The data also showed a dramatic cut-off in the number of terrestrial craters around 650 million years ago during the pre-firecrack. This is also a surprise, but as the authors wrote in the study there is a possible explanation:
Given the erosion rates on the stable continental terraces after 650 [million years ago]Similar conditions further back in time would have allowed most cremers of precocious age … to survive. Instead, the maze of Prakambrian craters coincides with major episodes of globally wide "snowball ground" glaciation. Pervasive subglacial erosion at approximately 650-720 [million years ago] Considered to have removed the continent's chest of materials, enough to remove most existing … Impact craters.
There is a fascinating opportunity, and further demonstration of the burgeoning snowball ground hypothesis.
That crater formation over the past 290 million years is 2-3 times higher than it was before the time of dinosaurs is surprising. But Mazroli offered a plausible statement:
"The increase in the impact rate may be due to a major breakup occurring in the main asteroid belt," she said. "When two large asteroids collide, they produce a swarm of fragments close to the impact space. They eventually move on to Earth – crossing orbits and a little end up hitting the moon and earth."
The timing of the Impact Spike is quite interesting, not just from an astronomical perspective. The apparent increase in impacts could have influenced the history of our planet. One of the greatest extinction events occurring around 250 million years ago – the permian-triassic mass extinction – occurred shortly after the perceived increase in the rate of asteroid impacts.
"However, we can't tell if there is no connection to this event," clarified Mazroy. "Our work sets the stage for other scientists to explore this issue and see if there are no correlations."
The Earth's more sensitive to asteroid strikes in 2019, as it was 300 million years ago, is something that could not be blunted by the data. "With our data we can say that the impact rate has increased in the past 290 million years," said Mazury, but her team is not able to "distinguish if there is just one spike, multiple spikes, or if this rate is still increasing. "For our sake, let's hope this isn't the last.
"I think their analysis is good, and they make a convincing case for an increase in the rate of asteroid impacts," Simone Marki, chief scientist at Southwest Research Institute at Boulder, Colorado, told Gizmodo. "The exact increase – a factor of two or three – may be less well-determined given uncertainties, but the proposed 2.6 seems to be based on available data." Marci said this noticeable increase is "inconceivable," and he is in agreement that "it may be the answer to a break up of an asteroid in the main belt."
Talked to Gizmodo"Ahmed J. Cavosie, a senior research fellow in science and engineering at Kurtin University, said the paper's performance on the rate of post-palaeozoic crater could be" accurate, but, model-driven, the study showed. Elsewhere, enough geological evidence. What's more, the researchers said the researchers worked under the somewhat unfounded assumption that the moon was "a reliable record of earth-scratching".
"This may be, but it's hard to confirm," Kawosie said. "The best way to appreciate their model is by acquiring better age and size estimates for terrestrial craters. This is the only record that we can conduct field studies and apply high-precision methods, but obviously, moonlighting is a bit tricky."
"Cavosie has recently discovered post-palaeoic impact craters with diameters of more than 10 kilometers, including all in Australia and Panasasma crater in Nicaragua," said their model, "adding that future explorers of older craters would ask."
"Overall, while the idea of a large increase in the number of asteroid implants is intriguing at the time, I do not think that the data cited by the authors strongly supports paper research," Jey Melosh, University distinguished professor of Earth, atmospheric And the planetary science of Purdue University relates Gizmodo.
"The authors rely on a clear lack of earth craters before about 300 million years ago, however, not that many old-age craters – about 180 confirmed craters at the present time – and the rocky area Are older than 300 million years is relatively small, so they are dealing with statistics of small numbers – a notoriously uncertain procedure.
Another issue of compulsion for Melosh was how the researchers measured the rate at which boulders ruin over lunar craters over time. He said they did not level the bollard because of the change in the rate of degradation in which the area around the crater cools after the sun sets or warms when it goes.
Melosh assumes that boulders break down at a constant rate through tiny meteorites that are exactly what – an assumption. It is extremely plausible, he said, the rate of degradation increases as the bumps get smaller.
"After all, smaller rocks take less energy to break up – and this may explain the lack of boulders around the craters before 300 million years ago, which the authors interpret as meaning that the craters are much older," said Melosh. "[O]Verbal, I don't think the case has been proven, nor has it been proven – this data is simply not good enough to greatly support their contingency, in my opinion. "
As for the idea that ice removed most of the Prekambrian craters, Kawosie said it was an "intriguing" possibility. The researchers demonstrated "temporary coincidence and a possible mechanism," he said, but "does not prove causality." What's more, more than two dozen Preecammary craters were known to exist, instead of describing the two in the new study.
The destruction of cremation by erosion, he said, creates a sedimentary record of shocked minerals (deformed by deep heat and pressure deformed minerals), which scientists have documented at Vrededeort and Saddam, the greatest pre-cambrian craters. If ancient glaciers "vacuumed up earth craters," Kawosie said, as sediments dating back to this period, "should be bursting at the seams" with shocked minerals. So "this is a testable hypothesis – go get your rock hammer!"
Mazroue and her colleagues have presented an intriguing new study, but it is clear that more work is strengthening their case. Recreating The record of asteroid impacts on Earth is important, both for the experience of our planet's geological history and for better expecting the influence of these catechismism impacts on the trajectory of life on the planet.[Science]