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# Catastrophe Calculator: Online Calculation of Asteroid Collision Outcomes

A new Arizona State University website allows visitors to calculate the results of a hypothetical collision by entering the dimensions and distance of a space rock, the visitor's distance from the collision site, and other parameters that create an outline of the destruction.

The history of asteroid collisions with the Earth remains, for the most part, a mystery to scientists. They can't even agree on whether a giant space rock hit the Yucatan Peninsula, Mexico, 65 million years ago, killing all the dinosaurs. Even astronomers cannot tell when the next catastrophic collision will occur. They just know it will happen sooner or later.

But now, anyone with a passing interest in the fate of the planet can take some of the mystery out of the outcome of the next collision. A new website of the University of Arizona allows its visitors to calculate the results of a hypothetical collision by entering the dimensions and distance of a space rock, the visitor's distance from the collision site and other parameters that create the outline of the destruction.

But beware: the removal of the mystery invites moments of fear and terror regarding the scope of the boom-and-buster, fireballs, falling skies and terrifying spirits created by a giant collision.

Prepare to be scared

Being something of a voyeur when it comes to natural disasters, I couldn't resist running a few scenarios through the disaster computer. If you continue reading, you will remember that the chances of a serious collision occurring in any given year are very low. A civilization-destruction-event, if it is possible, is almost certain not to occur in our lifetime (90 percent of all asteroids, large and close enough to do the job will be found in 2008) and even very improbable even in the next millennium.

But admittedly, throwing virtual giant rocks at the planet has its fair share of fun, and in this case at least, has more scientific significance than the average video game. I started by dropping a 15 kilometer wide asteroid - an estimate of the size of the suspect in the destruction of the dinosaurs - on San Francisco.

The results for the Bay Area are not good.

The resulting crater, 181 kilometers wide, tells us everything. The entire metropolis as a whole is gone before you can say where you left your heart… (in San Francisco…). What is indestructible is given a serious jolt by an earthquake measuring 10.2 on the Richter scale, the largest of all recorded earthquakes in history. Heat from a blazing fireball will turn most of the country and parts of other countries into toast.

The swift end of the Bay Area is even less severe compared to what will happen before the people of Los Angeles.

About 10 seconds after impact, radiation from the fireball will scorch Southern California, setting fire to clothing and wood in hand. In two minutes the ground beneath Hollywood will begin to shake. Weak brick structures will crumble. Concrete irrigation canals will be damaged, house frames that were not properly bolted to the foundation will fall apart. Even tree branches will fall. And only then will the mess begin.

Six minutes after the impact, most of the earth that was under San Francisco will be lifted up towards the atmosphere and will start to fall on the city of Los Angeles (and of course everywhere). Eventually, a thick blanket of ejecta at a depth of 5.5 meters will settle around the LA. Within half an hour of the cosmic impact, a wind will blow at a speed of 107 km/h (30 meters per second) that will spread everywhere what is left of Los Angeles.

"If you're close to a major impact site, bad things happen," said Jay Melosh, an expert on impact craters at the University of Arizona. Melosh supervises the development of computer programming. This should further help scientists and journalists who come to report on the dangers of asteroid impacts. "We could have added worse data, but it started to get horrible," he told Space.com.

I continued with the disaster scenarios to the west coast and crossed the country to Denver, where about a third of the way is covered in foot-thick ejecta with 35 mph winds. The residents of New York are spared so much commotion that they can sit comfortably and watch the disaster on the screens. (If videos are available at all). Nevertheless, about 13 minutes after impact, windows and doors will rattle in the east. After about 21 minutes, city-ruins fired from the largest crater in the DHA, will begin to fall as rain on the east, to create a blanket (layer) of half an inch over the city. About three and a half hours later a wind of about 13 km/h will arrive.

An object the size of the object that apparently wiped out the dinosaurs - (some researchers are not convinced it was the only cause) - is extremely rare, and it hits the Earth, perhaps only once every 300 million years.

Currently, no asteroid is known to be on a collision course with KDA. And experts agree that one of this size will almost certainly arrive with a warning range of decades or centuries, being easy to identify and locate before becoming a real threat. By then, the experts hope, methods will be developed to divert and destroy such an asteroid.

A more logical scenario

But what about something the size of the asteroid that created the meteor crater in Arizona? This 180 meter hole in the ground, now popular for tourism, occurred less than 50.000 years ago and was created by a space rock so small that if another one like it were to come to Earth, it would hit us before we could locate it.

The "criminal" from Arizona was a total of 20 meters wide. But instead of breakable stone it was mostly made of iron. Examples linked to the Impact Results online software show how to detail this more destructive material. A rock of this size (even though it is not so compressed) is supposed to hit the Earth once every 158 years, on average.

I replicated the data from the meteor crater in Newark, New Jersey, 16 miles from Manhattan as the crow flies. Location, of course, is everything. A crater nearly a mile wide was dug in New Jersey. A moderate earthquake with a magnitude of 4.7 shook the area. New York has suffered from such earthquakes in the past to a great extent. No ejecta hit Manhattan, and the winds reached an insignificant speed of about 6 km/h.

So I increased the risk factor - an asteroid the size of two football fields, although naturally stone-formed, is a different story. It opened a 3.4 kilometer wide crater in New Jersey. The resulting earthquake had a magnitude of 6.4 - enough to scare the city's emergency planners to death. A rock of this size hits Israel every 14.000 years.

Just estimates

Melosh developed the software together with fellow researcher Gareth Collins and graduate student Robert Marcus. Melosh said that the software is proving to be useful for scientists who would otherwise have to wade through cumbersome and complicated calculations to create a harm scenario for their research.

It is important to note that what actually happens when an asteroid hits the earth is not really known, because scientists have not actually witnessed any impact occurring to any degree. But they used computer models to find out probable impact results, and they also have some craters to explore in DHA.

Researchers assume that the heat sheet created by a cosmic collision will be similar to a nuclear explosion. In evaluating the results of thermal radiation, Melosh's team relies on a 1977 publication, The Impact of Nuclear Weapons, by the US Department of Defense and the Department of Energy.

"We determine, at a given distance, what kind of damage the radiation causes," said Marcus, who did most of the development of the software. "We have a description of when the grass will burn, when wood will burn or newspapers will burn and when people will suffer from second and third degree burns."

For earthquake prediction the researchers gather data from actual earthquakes in California and the knowledge of the culture and the distribution of earthquakes as sound waves through the planet. The global effects of an asteroid impact are more difficult to predict. Many scientists think that larger impacts will throw large amounts of dust into the atmosphere, causing a global winter that will last months or years. Melosh is skeptical about the dust.

"Nuclear bombs may pick up dust that is already there, but may not create it," Melosh said. He believes that most of the material fired into the surface is dissolved and then hardens into tiny, microscopic balls. "Most of the ejecta falls down within an hour". He calls the massive creation of the dust a "media myth".

And there is more

The software does not contain all the answers and much is left out. Melosh wanted the software to have practical use and is open to suggestions for improvement.

Important details for the impact - how the asteroid penetrates through the atmosphere to the earth - are simplified. And at least one effect is not taken into account: the (asteroid-driven) tsunami caused by an impact in the ocean (two-thirds of the Earth's surface is covered by water). Additionally, user-input results do not mention that wind speed cannot blow trees buried under the ejecta, nor if the trees have already burned and decayed.

Major and minor changes and improvements to the software may be based on input from other scientists, Melosh said. And in the coming weeks, his team will publish background information explaining the complicated calculations behind the software.

Robert Roy Britt. Translated by: Eli Ben David

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