Science

Story of an asteroid that hit Rajasthan millions of years ago

A breezy 110 km drive to the northeast of Kota in Rajasthan takes you to a huge impact crater that has kept researchers busy for years. Known as the Ramgarh structure, it is India’s third confirmed impact structure. Two recent papers have now yielded valuable information about the impactor and the condition of the region when it struck.

The international team collected rocks and impactite (rock created or modified by impact of a meteorite) samples from the rim of the crater, studied the chemical composition, and found them to comprise iron, copper, nickel and cobalt. They argue that a copper-rich iron meteorite could have been the impactor.

“The sedimentary rock of the area was found to be of the Mesoproterozoic age of about 1,600 to 1,000 million years ago. The impact event might have occurred into the palaeo-channel of the Parvati River, possibly into a shallow water environment during the Mesozoic Era, approximately about 165 million years ago. However, future radiometric age dating is needed for precise estimation of the impact event,” says Dr. Dwijesh Ray from the Planetary Sciences Division of Physical Research Laboratory, Ahmedabad. He is the corresponding author of the paper recently published in the Journal of Earth System Science.

“Also, the structure is roughly rectangular, unlike the simple, bowl shaped Lonar crater of Maharashtra. This structural pattern is roughly consistent with the oblique impact,” he adds.

Another study published in Meteoritics & Planetary Science reveals that the impact structure has an approximately 10 km diameter. The new findings aided by remote sensing and digital imagery shows the diameter to be much higher than the previously noted diameter of about 2.5 km.

This paper also notes that the asteroid may have hit into a shallow water environment. “We saw sediment deformation patterns and also gastropods embedded in the sedimentary rock. We know that these gastropods lived during the Middle Jurassic age, but more studies are needed to indicate the exact time of the impact,” explains Dr. Amar Agarwal from the Department of Earth Sciences at Indian Institute of Technology, Kanpur and one of the authors of the second paper.

Why study impact craters?

“The Chicxulub crater of Mexico which is about 170 km in diameter wiped out nearly 90% of life on earth. The Ramgarh structure could have had an effect on the flora and fauna of western Indian Subcontinent. This needs further study,” explains Dr. Agarwal. He adds that these craters could be sources of hydrocarbon and mineral deposits. The Vredefort crater of South Africa is rich in gold and Sudbury of Canada has platinum and other rare earth minerals. The minerals are not formed by impact craters. The pressure and temperature generated during an impact concentrate them.”

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Printable version | Sep 19, 2020 8:25:59 PM | https://www.thehindu.com/sci-tech/science/story-of-an-asteroid-that-hit-rajasthan-millions-of-years-ago/article32588607.ece

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