2024-03-28 18:27:58
The meteorite could have caused a fireball, a huge shock wave and fires that could have spread to the area where the people of the Indus Valley Civilization lived thousands of years ago.
“It would really be the equivalent of a nuclear bomb, but without the fallout,” says Gordon Osinski of Western University in Canada.
The 1.8 km wide crater, called the Luna Structure, has been known to locals in the state of Gujarat for some time. Scientists have studied it before – suspecting it was caused by an impact – but those studies were unsuccessful. Therefore, KS Sajinkumar from the University of Kerala in India went back with his colleagues to do more detailed research.
Geochemical analysis showed that the soil is rich in iridium, suggesting that the impact was most likely caused by an iron meteorite. The team also identified other materials typical of meteorites, including viustite, irsteinite, hercynite and ulvospinel.
David King of Auburn University in the US, who was not involved in the study, says that although the geochemical analysis seems to agree, the team still has not conclusively proven that it is a crater. To do that, they would need to find rocks that had been melted by the energy of the impact, he says.
“It’s not that I suspect it’s not a crater – but it would be good to have a standard line of evidence, with impactors,” says King.
But such materials are hard to find—and the area where they would be in Luna’s structure is usually underwater. KS Sajinkumar and his colleagues were only able to dig the trench during the very short dry season, but he says he plans to look for impactors in the future, calling this research “the tip of the iceberg.”
Mr. Osinski says that despite the fact that no impact material has been found, other evidence has led him to believe that the structure on Luna is an impact crater. “The authors did an excellent job with the samples they had,” he says.
Radiocarbon dating of the organic material beneath the presumed impact debris layer indicated that the plant material is about 6,900 years old. However, in follow-up work that has yet to be published, KS Sajinkumar and his colleagues conducted optically stimulated luminescence studies in the soil layer that revealed when the minerals last saw sunlight.
These tests, which were done not on the organic material beneath the debris layer but on pieces of the meteorite itself, have refined the date to about ]4050 years, says KS Sajinkumar. This means that the impact occurred around the time when the maturity stage of the Harappan civilization in the Indus Valley ended.
According to KS Sajinkumar, the impact should have caused a shock wave that would have reached a distance of about 5 kilometers, and the ejected material could have caused forest fires that affected a much larger area. G. Osinskis claims that the ash and particles thrown by the meteorite would have eclipsed the Sun for several days in some parts of present-day India.
“There would have been a fireball in the immediate vicinity, and then everything would have been swept away, for many kilometers,” he says.
The crater is located just 100 km from the archaeological site of Dholavira, which was the site of a Harappan city during this period. “If there were people living in that area, they would have suffered a serious loss,” King says.
KS Sajinkumar says this may have been the only impact of this magnitude ever experienced by a sufficiently advanced civilization.
The study is published žurnale „Planetary and Space Science“.
Let’s call it “New Scientist”.
2024-03-28 18:27:58