Translation of an Italian article dated October 30, 2007. - I hope that I did a correct translation...
On the scientific magazine "Terra Nova" had been published the work of a group of Italian researchers of the ISMAR-CNR and the Universities of Bologna and Trieste - Luca Gasperini, Francesca Alvisi, Gianni Biasini, Enrico Bonatti, Giuseppe Longo, Michele Pipan and Romano Serra - who led a scientific expedition on the site of the Tunguska event.[/i]
Studies show that the Lake Cheko, a small pound of about 500 meters of diameter, located about 10 Kilometers from the epicenter of the explosion of 1908, may be the crater caused by the impact of a "fragment" of about five feet, survived from the principal explosion who crashed in "low speed", that is about one Kilometer per second.
The principal explosion would occurred in the atmosphere, at 5-10 Kilometers above the Tunguska region, explains Luca Gasperini of the ISMAR-CNR of Bologna, this was the explosion of an asteroid or a comet of about 50-80 meters of diameter.
THE RESEARCH: "We carried out a sedimentological and geophysical study of the lake to see if its formation could be related to the event, and to detect the sequence of lake sediment geochemical and geophysical evidence from which to draw information on the nature of cosmic object" said Luca Gasperini of ISMAR-CNR.
"Several previous expeditions have already explored the area, but without find signs of impact or fragments.
Our field study has been carried out mainly using surveys of underwater acoustics, with a goal therefore more ambitious than the first Italian expedition in 1991, also organized by Professor Giuseppe Longo of the University of Bologna, and limited research of micro-cosmic object in the resin of trees. "
A DIFFERENT LAKE: During the expedition "Tunguska99" was therefore first investigated with sophisticated techniques and the morphology of the nature of the lacustrine deposits of the substrate, and collected sediment samples. "Thanks to these surveys - added the researcher - it was possible to find that the morphology of the lake is different from the common origin of Siberian lakes thermo-karst: the nature of the sediments recovered from the lake bed are compatible with hypothesis of "impact that would have occurred in a swampy forest with an underlying layer of permafrost (permanently frozen soil) is often over 30 meters."
"It was exactly the thawing of permafrost occurred short time after the impact to shaping the current size of the lake, and and hide the true nature of crater for all that long time.
This finding, if confirmed, will unravel the mystery of Tunguska, giving strong contributions, for understand the effects of the impact of an asteroid or comet on Earth."