Throughout Patagonia there are seven areas with proven evidence of meteorite impact. But the unique and little-known case of Bajada del Diablo, in Chubut, especially attracted the attention of the scientific community.
It is a field with about 200 craters or astroblemes. That is, they are craters that have been left by the impact of celestial bodies after colliding with the Earth.
This area of the Patagonian plateau covers an extension of 400 square kilometers in the center-north of the province of Chubut. It is the second in importance in the country. The first is Campo de Cielo in Chaco. However, Bajada del Diablo has great possibilities of positioning itself -according to a group of Argentine specialists- as one of the largest crater dispersion fields in the world.
-The crater field would have occurred between 130,000 and 780,000 years ago (Credit: CADIC / Conicet)–
“In Bajada del Diablo we found circular structures. We believe we have shown that it is an impact field produced by an asteroid or comet that has fragmented”, he commented to BLACK RIVER JournalRogelio Daniel Acevedo, PhD in Geological Sciences and one of the current forerunners of research in the sector.
The area was first described in 1987 by Dr. Hugo Corbella. From there, a long investigation process began to try to determine if they were indeed meteorite craters. It is that the fragments found in the area were very small.
Another difficulty that arose for verification was a particular rarity: the craters do not have any pattern, that is, they are scattered randomly. Normally when a meteor shower reaches the ground, the fragments are distributed in the form of an ellipse, where the largest fragments and the largest impact craters are concentrated at one end.
Acevedo recognized that these singularities made the analysis process – intensified during the last 20 years – difficult. However, the hypothesis gained strength when it was found that two different geological environments were affected.
“In general, Patagonia is covered by basalts, the Patagonian plateau is a volcanic rock. But there is another contiguous sedimentary environment that is also intervened, which gave us concrete indications. We also found microspherules, which are minor diagnostic elements,” he added..
Among the elements collected from the expeditions, they were able to find certain metals, such as iron or nickel, which are typical of an asteroid impact.
–A satellite view of Bajada del Diablo, one of the largest crater dispersal fields in the world (Credit: NASA)–
However, it is highly likely that the craters were caused by a comet -a body composed mostly of ice-. That would explain the lack of celestial particles of larger proportions.
When Bajada del Diablo would have originated
According to Dr. Acevedo and his assistant, Maximiliano Rocca, the phenomenon that would have produced it occurred between 130,000 and 780,000 years ago. In other words, it is an event from the middle of the Pleistocene, in the Quaternary period.
According to the scientists in an article published in the Natural History magazine of the Félix de Azara Foundation, the collision would have generated about 500 astroblemes on the current Chubut plateau. But today there is only a remnant of just over a hundred craters, between 60 and 360 meters in diameter, and between 30 and 50 meters deep.
What is the importance of studying these meteorites?
For Acevedo, meteorite research is based on two major particularities: the age of the rocks and their composition.
In the first place, the analysis of the conformation of the bodies that reach the planet allows us to presuppose a comparison of how the center of the Earth would be composed. “We have iron-nickel inside the nucleus, but we have never had a sample for study. Instead, asteroid meteorites sometimes collide with each other and easily reveal the composition of these metals,” he explained.
Besides, many of these materials are almost as old as the universe, which creates an “exciting mystery” with it. “They are rocks from the age of our solar system. There are no residual rocks on earth from that primitive Earth, but we do have them from the meteorites that arrive,” he added.
In particular, Bajada del Diablo is the only terrestrial field of multiple impact craters in volcanic basalts -the material that makes up magma-. This allows scientists to use it as a terrestrial analogue of conditions that existed on the Moon, Mars, Venus, and Mercury.
Is it possible to visit Bajada del Diablo?
Located about 200 kilometers from Trelew, Bajada del Diablo has a high tourist potential. However, because it is inserted in a remote area of the province, few visitors are received. There are even those who are unaware of its existence.
From the Government of Chubut, they have placed a special interest in promoting the area. Acevedo himself was called to make impact reports and surveys in order to attract the attention of the fans.
“If you go to Bajada del Diablo, there is a post in the middle of the steppe: there is a bar, a police station and two or three houses. But those who live there know very well where the craters are located,” explained Acevedo. The scientist recognized that it is the residents themselves who guide the foreigners.
In what other areas of Patagonia could there be meteorite craters?
According to a survey published in the journal spreading knowledge from the Patagonia of the National University of Comahue (UNCo), throughout the Patagonian territory there would be at least nine other circular structures that could have arisen from the impact of a celestial body.
However, it is noted that the verifications are still ongoing and it is not ruled out that other areas hitherto ignored are added. “None is proven, but everything can be. There will be some ideologues who will retrace our steps and say if some circular structures have chances to become future astroblemes,” said Dr. Acevedo.
Such is the case of the Niyeo Llama Structure, located in the southern region of Río Negro. O de Collón-Curá and Barda Negra in the center-south of the province of Neuquén.
On the latter, there are some important debates within the scientific community. However, Acevedo himself ruled out that it was the impact of a meteorite as previously assumed, through a detailed analysis of the crater. It is argued that it would have originated from the collapse of the soil itself, or that it is a drain.