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09 December 2011

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Asteroid Impact Calculator

 

For high-grade worry warts there’s now

a way to determine just what will happen

if their community is hit by a space invader

 

If an asteroid the size of a school bus gets through Earth’s atmosphere without breaking up it’s going to do some serious harm to wherever it lands.

 

 

For example, Barringer Crater (above), which sometimes referred to as Meteor Crater, was the landing pad for an asteroid about 40 m across. It excavated a hole in northern Arizona 1.2 km in diameter and 170 m deep.

 

That impact happened about 50,000 years ago, the blink of an eye on a geological scale, and scientists have calculated the energy released was the equivalent of 20 million tonnes of TNT. That’s about half the strength of the atomic bomb that killed 140,000 people in Hiroshima.

 

Calculator Lets People

Forecast Neighbourhood Impacts

Scientists at Purdue University and Imperial College London have developed a web-based program that allows people to figure out the damage likely to result from pieces of space rock of varying sizes.

 

As BBC News science correspondent Jonathan Amos points out (November 2010) “It will also tell you how far away you need to be to avoid being buried by all the material thrown out by the blast, or set on fire.”

 

The software is a development of an earlier program, the impact effects calculator, which was first released in 2004.

 

Calculate Local Destruction

Users can dial in a number of parameters, such as the size of a hypothetical asteroid, angle of approach, speed, and distance from impact.

 

Suppose a chunk of space rock the size of a refrigerator pounds into the sidewalk at the corner of Maple and King, Impact Earth will tell users how far away they need to scuttle away to be safe.

 

And, should the interested party be lounging on a beach and want to ruin a perfectly good holiday, the calculator will also generate a tsunami wave height should the asteroid splash down in the ocean.

 

Many Asteroids Pose Potential Danger

There are millions of bits of rock whizzing about the asteroid belt and almost all of them remain safely glued in orbit far away from our planet.

 

The National Aeronautics and Space Administration (NASA) has so far counted more than 7,000 asteroids, comets, and meteorites that have developed minds of their own and escaped to become what astronomers call Near Earth Objects. However, “near” to a space scientist is measured in Astronomical Units (AU); one AU is equal to about 150 million kilometres.

 

NASA keeps tabs on all the known problem rocks and says collisions of the scale of the one that dug out the Barringer Crater “occur once or twice every 1,000 years.”

 

Low Probability of Collision

So, the advice is not to lose sleep over something with a very low probability of happening, although there are occasional surprises.

 

In March 2009, an asteroid called DD45 came within 63,000 kilometres of Earth and was only spotted three days before its fly-by.

 

An impact from this 60-metre rock would have been devastating; the Tunguska Asteroid that walloped Siberia in 1908 was smaller and it demolished 60 million trees.

 

So, let’s see: 60-metre diameter times 20 km/sec with an angle of approach of 45 degrees? Wonder if there are any caves in Waziristan that bin Laden’s lot haven’t filled up yet.

 

Sources

“Impact Catastrophe Calculator Updated.” Jonathan Amos, BBC News, November 3, 2010.

Impact Earth, Purdue University.

Near Earth Object program. NASA

 

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