Decoding the Shiva impact

 

 

 

Let’s first understand what Dr Chatterjee’s Shiva Crater and the debate is.

 

It is a crater submerged in the Arabian Sea, to the west of Mumbai, around the Bombay High. According to Dr Chatterjee’s team, it was made by the impact of an asteroid, about 40 km in diameter, 65 million years ago, around the same time as Chicxulub crater was formed 15,000 km away in Mexico. So, he proposed that formation of these two craters triggered a Mass Extinction event at the end of the Cretaceous-Tertiary period (also called K-T extinction). And that it killed the dinosaurs and 75 per cent of animal and plant species found then, both on land and in sea. That’s why he named the crater after Shiva, the Lord of destruction and creation.

 

He paints a picture of the “catastrophe” that it was, “The Shiva crater is about 500 km in diameter. Such craters are well known in the Moon and Mars. If confirmed, it will be the largest impact crater ever known on this planet. So, understandably, its impact was huge. The energy generated by the crater would be about 10,000 times greater than whole of world’s nuclear arsenal put together. It turned rocks into lava, some even turned into powder. The shock gave peculiar textures to minerals in this region.”

 

 

At the heart of the debate is the genesis of the Shiva crater, Is it an impact crater, after all?

 

Dr Chatterjee explains where his hypothesis is falling short: “It is now well accepted in science that large meteorites not only destroyed life, but also created the first life on earth. But the crucial piece of evidence missing here is the documentation of shock features in the target rocks, which are about 4 km deep in the Arabian Sea. There is a great logistic problem to drill samples from such a depth; it would cost millions and millions of dollars. 

 

Moreover, the Bombay High, the central peak of the Shiva crater, is the largest oil field in India; it is hazardous to drill and retrieve the core samples from an active oil field for further analysis. There was no such issue with the Chicxulub crater in Mexico, yet it took us almost 10 years to confirm the impact signature from drill core samples. Most likely a large asteroid split into two, one crashed on the Yucatan peninsula in Mexico, the other near the Mumbai coast. Incidentally, if you look a paleogeographic map, the locations of the two craters 65 million years ago were almost antipodal, exactly on the two sides of the globe.”

 

So far, Dr Chatterjee’s team has identified iridium anomaly and shocked quartz at the KT boundary sections of India, demonstrating the evidence of a proximate impact site. However, he is hopeful the Koyna Drilling Project (to study reservoir-triggered earthquakes), which he is coming to India for, will find the missing links. 

 

“The project is close to the eastern rim of the Shiva crater, so it may provide us the most crucial evidence. I’ll be working with the NGRI (National Geophysical Research Institute) scientists at Hyderabad, who are responsible for the project. Also, scientists from the National Institute of Oceanography will help me.”

 

 

Though Dr Chatterjee shifted base to the US in 1976, he continues his collaboration with scientists at Indian Statistical Institute (ISI), Kolkata. He will even set up a natural history museum at the Visva-Bharti University as part of the Fulbright grant because he feels children should not be deprived of the knowledge of “basic science like human evolution”. Dr Chatterjee, who has won laurels of “The Best Teacher” and “Scientist of The Year” in the past, says that “it’s the lack of research in basic science that is holding India back.”

 

His fascination with dinosaurs and early predators started as a student of Jadavpur University, where he was studying geology. He first became interested in paleontology, when a British scientist of London University, Dr Pamela Robinson came to Kolkata and founded a research center at the ISI, mainly to explore dinosaurs. As a student of Dr Robinson, he discovered many dinosaurs from the Godavari of India. He then went to London University to finish part of his doctoral work under her guidance while continuing his research at ISI. He shifted base to the States when he was invited as a professor at the University of California, Berkeley.