On the 30th June 1908 at around 7.17am, “a large space rock, about 120 feet across, entered the atmosphere of Siberia and then detonated in the sky” levelling approximately 80 million trees over 800 square miles. The remoteness of the site meant that few if any people died in the Tunguska event itself – but that wouldn’t have been the case if it had happened over a major city. The BBC article quotes Armagh Observatory’s Mark Bailey, “Everything within the M25 would have been wiped out”. At the time dust from the fireball resulted in bright night skies over Europe – “In London, it was possible to read newspapers and play cricket outdoors at midnight.” Near Earth Objects are now the subject of extensive study, while the University of Bologna website has a dedicated area on all things Tunguskan. Back to the NASA article Adds NASA have a podcast version [mp3 file] of the article here.
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. In 1927, a new expedition, again lead by Kulik, reached its goal. “At first, the locals were reluctant to tell Kulik about the event,” said Yeomans. “They believed the blast was a visitation by the god Ogdy, who had cursed the area by smashing trees and killing animals.”
And the NASA article ends by noting the expected frequency of such events..
[Don] 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.
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.”