The Tunguska air blast A century ago, on June 30, 1908, an asteroid or comet hurtled into Earth's atmosphere and exploded over Siberia, flattening 2,000 square kilometers of forest. Credit: © Don Davis. All rights reserved.
Importance : The Beginning of all discussion – About Asteroid – Tunguska :
"If you want to start a conversation with anyone in the asteroid business all
you have to say is Tunguska," said Don Yeomans, manager of the Near-Earth Object Office at NASA's Jet Propulsion Laboratory. "It is the only entry of a large meteoroid we have in the modern era with first-hand accounts."
On the Day of The Event – A Man and Many Others – Eyewitnesses :
At around 7:17 on the morning of June 30, 1908, a man based at the trading post at Vanavara in Siberia is sitting on his front porch. In a moment, 40 miles from the center of an immense blast of unknown origin, he will be hurled from his chair and the heat will be so intense he will feel as though his shirt is on fire. The man at the trading post, and others in a largely uninhabited region of Siberia, near the Podkamennaya Tunguska River, are to be accidental eyewitnesses to cosmological history.
The First Scientific Expedition - Led by Mr.Leonid Kulik :
While the impact occurred in '08, the first scientific expedition to the area would have to wait for 19 years. In 1921, Leonid Kulik, the chief curator for the meteorite collection of the St. Petersburg
museum led an expedition to Tunguska. But the harsh conditions of the Siberian outback thwarted his team's attempt to reach the area of the blast.
SECOND SCIENTIFIC EXPEDITION AFTER 6 YEARS : In 1927, a new expedition, again l ead by Kulik, reached its goal.
Reluctance of Locals – Blast Visitation by the God Ogdy :
"At first, the locals were reluctant to tell Kulik about the event," said Yeomans. "T hey believed the
blast was a visitation by the god Ogdy, who had cursed the area by smashing trees and killing
animals."
First Impressions of team on Second Expedition to the Site :
While testimonials may have at first been difficult to obtain, there was plenty of evidence lying
around. Eight hundred square miles of remote forest had been ripped asunder. Eighty million trees were on their sides, lying in a radial pattern.
"Those trees acted as markers, pointing directly away from the blast's epicenter," said Yeomans.
"Later, when the team arrived at ground zero, they found the trees there standing upright -- but their limbs and bark had been stripped away. They looked like a forest of telephone poles."
Such de branching requires fast moving shock waves that break off a tree's branches before the
branches can transfer the impact momentum to the tree's stem. Thirty seven years after the Tunguska blast, branchless trees would be found at the site of another massive explosion -- Hiroshima, Japan.
Kulik’s Expedition – talk with a person based in Vanar trading Post :
Kulik's expeditions (he traveled to Tunguska on three separate occasions) did finally get some of the locals to talk. One was the man based at the Vanara trading post who witnessed the heat blast as he was launched a few yards.
His account: Suddenly in the north sky… the sky was split in two, and high above the forest the whole northern part of the sky appeared covered with fire… At that moment there was a bang in the sky and a mighty crash… The crash was followed by a noise like stones falling from the sky, or of guns firing. The earth trembled.
The massive explosion packed a wallop. The resulting seismic shockwave registered with sensitive barometers as far away as England. Dense clouds formed over the region at high altitudes which reflected sunlight from beyond the horizon. Night skies glowed, and reports came in that people who lived as far away as Asia could read newspapers outdoors as late as midnight. Locally, hundreds of reindeer, the livelihood of local herders, were killed, but there was no direct evidence that any person perished in the blast.
THE CONTINUED DEBATE – HERE IS WHAT WIDELY ACCEPTED - THEORY :
Space Rock – Detonated in Sky :
"A century later some still debate the cause and come up with different scenarios that could have
caused the explosion," said Yeomans. "But the generally agreed upon theory is that on the morning of June 30, 1908, a large space rock, about 120 feet across, entered the atmosphere of Siberia and then detonated in the sky."
Speed 33,500 miles per hour – Extreme Temperature :
It is estimated the asteroid entered Earth's atmosphere traveling at a speed of about 33,500 miles per hour. During its quick plunge, the 220-million-pound space rock heated the air surrounding it to 44,500 degrees Fahrenheit.
Why Did it Blast in the Sky ?
At 7:17 a.m. (local Siberia time), at a height of about 28,000 feet, the combination of pressure and heat caused the asteroid to fragment and annihilate itself, producing a fireball and releasing energy equivalent to about 185 Hiroshima bombs.
"That is why there is no impact crater," said Yeoman’s. "The great majority of the asteroid is
consumed in the explosion." Yeomans and his colleagues at JPL's Near-Earth Object Office are tasked with plotting the orbits of present-day comets and asteroids that cross Earth's path, and could be potentially hazardous to our planet.
Once in Every 300 Years Tunguska Sized Asteroid enters Earth :
Yeomans estimates that, on average, a Tunguska-sized asteroid will enter Earth's atmosphere once every 300 years. On this 100th anniversary of the Tunguska event, does that mean we have 200 years of largely meteor-free skies?
"Not necessarily," said Yeomans. "The 300 years between Tunguska-sized events is an average based on our best science. I think about Tunguska all the time from a scientific point of view, but the thought of a another Tunguska does not keep me up at night."
Lonar Impact Crater in India : This one of the important impact crater situated in State of Maharastra,India. The Age of the crater is stated to be over 50,000 years. This Crater is second in line after Barringer Crater in USA if diameter of the crater is taken into considereation.
Society's Study - Student Activity :
Society presently has record over 175 Impact Craters across the World. These records were compiled for proper understanding of the subject and to plan a major activity in coming months involving Students.
Suprising find : During above study for compilation of Data. President of SEDS INDIA Mr.Pradeep submitted the case of crater called "SHIVA CRATER". Society already in touch with experts on this crater to present you information in our next article.
WHAT IS SHIVA CRATER ?
The Shiva crater is an ancient sea floor structure located beneath the Indian Ocean, west of Mumbai, India. It was named by the paleontologist Sankar Chatterjee after Shiva, the Hindu god of destruction and renewal.
According to the impact hypothesis, it formed around 65 million years ago, at about the same time as a number of other impact craters and the Cretaceous-Tertiary extinction event (K-T boundary). Although the site has shifted since its formation because of sea floor spreading, the formation is approximately 600 kilometers long by 400 km wide. It is estimated that a crater of that size would have been made by an asteroid or comet approximately 40 km in diameter.
HOWEVER THERE IS ONE IMPORTANT QUESTION WE HAVE TO ASK OURSELVES - ARE WE PREPARED TO TACKLE THE NEXT VISIT OF SUCH ASTEROID OR COMET ?
HOW DO WE PREVENT SUCH AN IMPACT ?
IS ANY ONE IN INDIA OR ASIA LISTENING?
PRESENTLY VERY FEW COUNTRIES ARE WORKING TO FIND SOLUTIONS.
WE HOPE THIS 100TH ANNIVERSARY ACTS A GREAT REMINDER TO THE WORLD.
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