Tunguska: One Blast. 80 Million Trees. No Crater.Episode 121:55
The Blast Heard by Machines in Europe
Researchers interrogate Tunguska's surviving seismic and infrasound traces to constrain an explosion witnessed mostly through stories.
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Transcript
A herder was blown into a tree and later died.
Blast came over Siberia June 30th, 1908, around 7:15 a.m.
It occurred in one of the remotest areas of Siberia.
Residents of distant villages and trading posts reported: The windows are breaking; move away from the wall.
Seismic instruments hundreds of miles away recorded shock wave tremors. The room held its breath around the trembling instruments.
At 37 miles, or 60 kilometers, people fell, windows broke.
Farther away, distant instruments measured the same wave.
Infrasound detected the strike in Russian Siberia and Europe. A seismic signal was also recorded at Irkutsk.
Seismic and infrasound data support 10 to 20 megatons.
Tunguska has fewer than 100 eyewitness anecdotes. The quiet record leaves an unresolved space behind.
A 2018 NASA workshop drew 12 international experts plus 40 others.
Meeting re-examined Tunguska through competing scientific models.
Modern models place the explosion 6 miles, or 10 kilometers, above ground.
Model fits cluster around 10 to 15 megatons.
A witness at the Vanavara trading station said: I saw the sky split in two, and fire covered the northern sky.
2018 workshop called forest health a major uncertainty.
Forest health, topography, wind assumptions and signal coupling remain uncertainties.
Modern models put 10 to 20 megatons in an airburst 6 miles, or 10 kilometers high.
The evidence narrowed the range of competing impact models.
Results suggest events may occur millennia rather than centuries apart.
Where it leaves off
If Tunguska released 10 to 20 megatons, scientists now had to ask how often such an object reaches Earth.
Next: Episode 13, The Disaster That Returns Every 2,000 Years
Sources
- 1908 SIBERIA EXPLOSION: Reconstructing an Asteroid Impact from Eywitness Accounts - Planetary Science Institutepsi.edusecondary
- 115 Years Ago: The Tunguska Asteroid Impact Event - NASAnasa.govsecondary
- NASA/Technical Memorandum (NASA/TM--220174) 2018ntrs.nasa.govsecondary
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