Tuesday, April 12, 2005
Look Up!
Aping America's color-coded terror warnings, astronomers at MIT have overhauled the Torino Scale used to measure the likelihood of Earth's doomsday collision with comets and asteroids. The new chart has a colored scale from zero to ten. It goes from harmless white to blazing chimney red for the "certain global catastrophe" warning.
Perhaps most interesting is Level 8, the first of the chart's three red alerts. It will be called when "a collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if close offsore. Such events occur on average between once per 50 years and oncer per several 1000 years," the chart says.
Uh oh. The Tunguska meteorite, a likely Level 8 event, exploded above the Taiga in 1908, nearly a century ago. It felled an estimated 60 million trees over 2,150 square kilometres but did not leave a crater. The impact was felt as far away as 1,000 kilometres. At 500 kilometres, witnesses had claimed to have heard a deafening bang and to have seen a cloud on the horizon. The power of the blast was estimated between 10 and 15 megatons of TNT, about the size of the Hiroshima bomb.
The scientists aren't worried. They said that the highest Torino level ever given to an asteroid was a four (yellow) last December, with a 2 percent chance of hitting Earth in 2029. After extended tracking of the asteroid's orbit, it was reclassified to level zero.
Perhaps most interesting is Level 8, the first of the chart's three red alerts. It will be called when "a collision is certain, capable of causing localized destruction for an impact over land or possibly a tsunami if close offsore. Such events occur on average between once per 50 years and oncer per several 1000 years," the chart says.
Uh oh. The Tunguska meteorite, a likely Level 8 event, exploded above the Taiga in 1908, nearly a century ago. It felled an estimated 60 million trees over 2,150 square kilometres but did not leave a crater. The impact was felt as far away as 1,000 kilometres. At 500 kilometres, witnesses had claimed to have heard a deafening bang and to have seen a cloud on the horizon. The power of the blast was estimated between 10 and 15 megatons of TNT, about the size of the Hiroshima bomb.
The scientists aren't worried. They said that the highest Torino level ever given to an asteroid was a four (yellow) last December, with a 2 percent chance of hitting Earth in 2029. After extended tracking of the asteroid's orbit, it was reclassified to level zero.
