This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

08 November 2007

Journal Article: "A possible impact crater for the 1908 Tunguska Event"

Summary from

"A team of scientists from the Marine Science Institute in Bologna [Italy] claims to have found the crater left by the aerial blast of a comet or asteroid in 1908 in the Tunguska region of Siberia. The blast flattened 770 square miles (2,000 square kilometers) of forest, but to date no remains or crater have been found. This has left open the question of what kind of object made the impact. The team believes that, contrary to previous studies, nearby Lake Cheko is only one century old and 'If the body was an asteroid, a surviving fragment may be buried beneath the lake. If it was a comet, its chemical signature should be found in the deepest layers of sediments.' The team's findings are based on a 1999 expedition to Tunguska and appeared in the August issue of the journal Terra Nova."

Journal Reference:

Terra Nova, 00, 1–7
Volume 19 Issue 4 Page 245-251, August 2007
"A possible impact crater for the 1908 Tunguska Event"
Luca Gasperini, Geologia Marina, Istituto di Scienze Marine, CNR, Via Gobetti 101, Bologna 40129, Italy. Tel.: +39 051 639 8901; fax: +39 051 639 8901; e-mail:

The so-called ‘Tunguska Event’ refers to a major explosion that occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2000 km2 of taiga, globally detected pressure and seismic waves, and bright luminescence in the night skies of Europe and Central Asia, combined with other unusual phenomena. The ‘Tunguska Event’ may be related to the impact with the Earth of a cosmic body that exploded about 5–10 km above ground, releasing in the atmosphere 10–15 Mton of energy. Fragments of the impacting body have never been found, and its nature (comet or asteroid) is still a matter of debate. We report results from the investigation of Lake Cheko, located ~8 km NNW of the inferred explosion epicenter. Its funnel-like bottom morphology and the structure of its sedimentary deposits, revealed by acoustic imagery and direct sampling, all suggest that the lake fills an impact crater. Lake Cheko may have formed due to a secondary impact onto alluvial swampy ground; the size and shape of the crater may have been affected by the nature of the ground and by impact-related melting and degassing of a permafrost layer.

Link: National Geographic Article

Link: Terra Nova Journal (August 2007)

Link: Terra Nova Journal Article

Link: Terra Nova Journal Article PDF

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