Here's a story that just hit our radar screen, and we wanted to share the news immediately rather than wait for further facts to come out. In the online journal
Terra Nova, a team of Italian researchers led by marine geologist Luca Gasperini reports on what may be the missing Tunguska impact crater.
Tunguska is a household name for meteorite enthusiasts. It's the best-known destructive impact to have occurred in the modern era, a blast that destroyed some 800 square miles of remote forest near the Tunguska River in eastern Siberia on the morning of June 30, 1908. Something - a small asteroid or comet - entered the atmosphere and exploded with a force equal to about 15 million tons of TNT. That's 1,000 times more powerful than the atomic bomb dropped on Hiroshima, Japan. Experts think the blast occurred some 5 miles above the ground, and - here's the catch - no crater, not even the tiniest trace of the impactor, has ever been found.
Gasperini's team suspects that
Lake Cheko, located some 5 miles north-northwest of the blast's suspected epicenter was gouged out when the impactor struck and later filled with water. The region is remote, and it's unclear from old maps whether the lake existed before 1908.
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| ©Google Earth
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| Lake Cheko
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The team's investigation of the lake bottom's geology revealed a strange funnel-like shape that differs from those of neighboring lakes but is consistent with an impact origin. They go on to say that it might have formed from a fragment of the main-body explosion.
They hope a future drilling effort will settle the mystery. We'll dig a little deeper too and share more as we learn it.
Comment: Here is the conclusion of
the study cited above:
Cheko, a small lake located 8 km from the alleged epicentre of the 1908 Tunguska Event, has an unusual funnel-like bottom morphology, with 50 m maximum water-depth near the center and a 0.16 depth-to-diameter ratio. This morphology is different from that of subarctic Siberian thermokarst lakes, and is also hard to be accounted for other 'normal' Earth-surface tectonic or erosion/deposition processes, but is compatible with the impact of a cosmic body. Based on diameter, depth and morphology of the lake crater, and assuming that the impacting object was an asteroid, a mass of 1.5 × 106 kg (10 m diameter) was estimated for the projectile. However, this estimate is probably too large, because the crater was enlarged by permafrost melting and release of H2O, CH4 and other volatiles induced by the impact into a soggy ground. The projectile that formed Lake Cheko might have been a fragment of the main body that exploded in the atmosphere 5 - 10 km above ground. A prominent reflector observed in seismic reflection profiles 10 m below the bottom at the center of the lake indicates a sharp density/velocity contrast, compatible with either the presence of a fragment of the body, or of material compacted by the impact. Drilling could solve this dilemma.
Very interesting that the lake is an oval, exactly like the Carolina Bays, which are likely resultant from exactly the same thing - ejecta from a large meteorite impact.
It would be interesting to see if any other area lakes are ovals with the same orientation - and what the orientation of this lake is to the 'suspected impact point' - i.e., the center of the destruction.