Magnetic and seismic reflection study of Lake Cheko, a possible impact crater for the 1908 Tunguska Event

Abstract

[1] A major explosion occurred on 30 June 1908 in the Tunguska region of Siberia, causing the destruction of over 2,000 km 2 of taiga; pressure and seismic waves detected as far as 1,000 km away; bright luminescence in the night skies of Northern Europe and Central Asia; and other unusual phenomena. This "Tunguska Event" is probably 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 here results from a magnetic and seismic reflection study of a small ($500 m diameter) lake, Lake Cheko, located about 8 km NW of the inferred explosion epicenter, that was proposed to be an impact crater left by a fragment of the Tunguska Cosmic Body. Seismic reflection and magnetic data revealed a P wave velocity/magnetic anomaly close to the lake center, about 10 m below the lake floor; this anomaly is compatible with the presence of a buried stony object and supports the impact crater origin for Lake Cheko.

Tunguska dark matter ball

“…So we take a typical speed of v = 1 2 220 2 + 1 2 60 2 km/s = 1.6 * 10 5 m/s (2) for the balls making up the dark matter. The two contributions are taken crudely to be equal, in correspondence with our estimate of the density near the earth being just double that of the halo proper.…”

“…There are strong indications [2,29] that Lake Cheko is the site where the extra-terrestrial object hit the solid surface of the earth, and we shall assume that to be the case. The epicentre of the explosion, as indicated by the tree falling pattern, is however 10 km to the south-east of Lake Cheko.…”

The origin of Lake Cheko and the 1908 Tunguska Event recorded by forest trees

“…). Data collected during the Tunguska99 expedition led us to formulate the hypothesis that the lake fills a crater produced by the impact of a TCB fragment, which survived the atmospheric explosion and hit the ground downrange of the main body (Gasperini et al ., , , ). However, based on theoretical models and comparison with typical impact craters, Collins et al .…”

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“…The comet hypothesis had not been widely accepted [19], as it is not understood how a comet could penetrate to near the surface of the Earth. Moreover, debate about the presence of an impact crater continues, with the most recent (May 2012) study concluding in favor of Lake Cheko as representing a small (diameter ∼ 500 m) impact crater [15,16], about half the diameter of the above described Meteor Crater. Tunguska features are compatible with the cometary CUDO event properties: an icy matter surrounding the core along with a strongly gravitating central CUDO body would provide the enhanced stability necessary.…”