Is Earth Near to Doomsday…
A mysterious space visitor streaked past Earth at 21,000 mph yesterday. (In fact the object was moving slightly slower than the returning Apollo capsules did from the manned moon missions.)
Shuttling between the orbits of Mars and Venus, the vagabond swept within 76,000 miles of Earth at 7:46 a.m. EST.
But speaking of doomsday predictions, what would have happened if the object had slammed into Earth yesterday? What would today’s headlines read?
It depends if the object is natural or manmade. Ian reported
that some scientists think it might be the discarded rocket booster from the European Space Agency’s Venus Express
Assuming it is an asteroid with the density of rock, it would be 30 feet across. As it plowed into our atmosphere, all of the asteroid’s kinetic energy would have been converted into light, sound, and heat under a crushing deceleration dozens of times the normal pull of gravity. The atmospheric stresses would probably have been severe enough to break up the asteroid. It would have momentarily blazed brighter than the sun as it unleashed as much energy as 30,000 tons of TNT exploding. That’s the same as exploding two Hiroshima-sized atom bombs.
Statistically, atmospheric explosions by falling debris should seriously damage or destroy a commercial airliner once every 50 years.
The Scale and Frequency Guide to Earth impacting Space Debris
Microscopic objects: interplanetary dust grains slow to a halt in the upper atmosphere and gently settle to the ground, depositing 120 tons per day as meteoric dust. (And I just washed the car!)
Pebble to baseball sized objects: This is the range for meteors or so-called “shooting stars.” They are heated by friction as they enter the atmosphere, become incandescent, and vaporize. The biggest in the range can momentarily become as bright as Venus.
Dining room table sized objects: These often fragment in the atmosphere and scatter pieces on the ground as meteorites. Meteors that blow apart lower in the denser atmosphere often emit sonic booms. Defense satellite data show that Earth collides with such objects several times a year. Statistically, at least one car per year should be hit by a meteorite. (And I just got a new paint job!)
Large building sized objects:
These come along every century or two. An aerial disintegration and explosion would be powerful enough to level a major city. The Tunguska, Siberia fireball of 1908
was one such event.
Football-field sized objects: These visitors may come once every 1,000 year and unleash energies comparable to largest nuclear weapons. They will blast out mile-wide craters and burn everything within a few miles of the impact site.
Small town sized objects: These once in a million year visitors release energies comparable to thousands of large nuclear weapons all going off at once. They will blast out a crater over 10 miles across. All life within at least 100 miles of ground zero will be extinguished. Ejecta will devastate the landscape even farther beyond the crater.
: These are dinosaur-killer
class asteroids, as recorded in the geologic strata from 65 million years ago. Their impact energies far exceed the total nuclear arsenal at the peak of the Cold War. The titanic blast will demolish an entire continent. Dust raised by the impact will have devastating global climatic effects and trigger mass extinctions. These impacts happen every 10 to 100 million years.
Large state-sized asteroids
: Not to worry you “2012” soothsayers
, this hasn’t happened in 4 billion years. The impact would vaporize enough rock to cover the earth, sterilize the surface and boil away much of the atmosphere.