What damage would an Asteroid Impact cause?
A near earth Object (NEO) does not need to be large to devastate. One the size of a small garage would annihilate a large city. One big enough to leave a 10km crater, still nowhere near the size of the biggest (there is a 300km crater on Earth), would have the destructive force of every one of the world’s 10,000 nuclear warhead combined.
The Asteroid that destroyed the Dinosaurs
It is thought that 65 million years ago in what is now Yucatan the impact at a velocity of 11 km/second of a 10-kilometer wide asteroid is what helped to bring about the K-T extinction, whereas no land animal with a size greater than the size of a small chicken was able to survive.
Those that study this time frame believe that if man had inhabited the planet at this time, he surely would have been destroyed by this particular event. This event threw huge amounts of matter into the atmosphere in addition to this, it caused 2000 foot waves that may have all but completely emptied the Gulf of Mexico. This event created months of darkness (which interfered with photosynthesis) and much cooler temperatures globally, and the resulting harsh conditions which in turn led to the extinction of many species, including the last of the dinosaurs.
Although this is quite compelling as a hypothesis, it remains controversial and has broad but not total acceptance within the scientific community. It is an estimate that impacts of asteroids as large as the one thought responsible for the K-T extinction occur about once every hundred million years.
Documented & Studied Impacts and Events
On the date of June 30th, 1908, at about a quarter after 7:00 a.m., a very mysterious explosion occurred in the skies over Tunguska, Siberia, located in Russia. This explosion happened at anywhere between six-to-eight kilometers from ground zero, and the resultant action in this was to lay waste to a vast region of pine forest of 2,150 square kilometers, felling more than 60 million trees. This was seen as a brilliant burst of light from the inhabitants of the region of 50 kilometers around. Witnesses claim that the explosion was so loud and powerful as to blow-out windows, temporarily blind and knock people to the ground, and sounded like a deafening roar. Had it happened fifty years later, it is surmised by scientists, (placing it within that time-frame of the Cold-War) it would most likely have spurred that nation into a nuclear war.
In 1972, an estimated 1000-ton object skimmed upon the edge of Earth’s atmosphere over the Grand Tetons National Park in Wyoming, and then skipped back out into space, like a skimming-stone off water.
This event was photographed by tourists and also was detected by Air Force satellites. Had it approached at a 90° angle into the atmosphere, it most likely would have caused a Hiroshima-scale explosion over Canada, only a bit down-sized from the scale of the Siberian blast.
In 1992, a meteorite weighing 12.4 kg. was recovered after it had made a spectacular appearance over Peekskill, N.Y., where it was described as being as bright as a “full-moon”. This event was recorded by 16 separate video cameras, some of which were located at a local high-school football game and were recording the game!
On January 19, 1993, a very bright asteroid crossed the sky of Northern Italy, ending with an explosion approximately over the town of Lugo, Italy. The explosion (14 kilotons of energy) generated shock waves which were recorded by six local seismic stations. This particular type of asteroid did disintegrate at a great altitude, which is quite lucky for the town of Lugo. Had it been an the type of asteroid that would have been composed mostly of iron ferrites, of which only some 6% of all asteroids are known to be comprised as such, chances are that it would have disintegrated at a much lower altitude creating a great deal of death and destruction.
In 1994 the US Department of Defense made public domain its records on energetic bolide-type asteroids over a time span of about twenty years. This data indicates that, from 1975 to 1992, there were 136 airbursts of energy greater than 1 kiloton, but the real number was probably at least 10 times higher, because the satellite system does not cover the entire surface of the Earth.
What would happen during a large collision?
In 1994 a large comet (P/Shoemaker-Levy 9) hit Jupiter. The Hubble telescope recorded the impact with tremendous accuracy. As it entered the atmosphere of Jupiter temperatures reached over 20,000 degrees. The impact sent a fireball thousands of miles into space. [Image compliments of the-planet-jupiter.com. A magnificent artist rendering of Shoemaker-Levy 9 breaking up, and impacting into Jupiter] The scale of the impact may look small in scale, but bear in mind the size differential between Jupiter and Earth.
The damage of an impact on Earth would kill all life. Massive earthquakes would jet out around the globe at thousands of miles an hour, destroying all buildings and life in their path. It would also trigger volcanic activity setting off eruptions and explosions all over the world. An enormous dust cloud would be sent into the atmosphere. A fireball would be sent into the sky miles tall. Any life that had survived the inital impact would be overcome with a whole new set of problems. Peices of the earth and dust would block the atmosphere, preventing the earth from getting any sun. Plant life would become extinct, and humans would face the horrifying reality of a nuclear winter.
How many asteroids do we have to worry about?
Hundreds… thousands. The largest yet discovered are an awesome 18 miles in length. Scientists estimate that there could be as many as 1000 asteroids larger than 1 mile across that pass relativly close to Earth. An impact by any one of these would be an Extinction Level Event.
How often is Earth hit by an asteroid?
More frequently than you may think. An incident like Tunguska occurs approximately once per every hundred years. Smaller ones, but easily big enough to take out a large city, occur at least 3 times per century, for example Brazil in 1930. While most of the recent recorded impacts have happened in places that were barely inhabited, we won’t always be that lucky. If the Tunguska event had happened over the city of New York it would have been nearly leveled.
Those large enough to cause extinction, 1/2 mile in diameter, occur less frequently – around once per million years. No large scale asteroids or meteors have been found to have an earth crossing path, but the number of people looking compared to the number that may be out there is majorly lopsided.
How could we stop an Imminent Impact?
Up until 50 years ago, we would have been totally defenseless against one. With the advent of nuclear weapons, we might have the possiblity of lauching ICBM nuclear tipped rockets at it, in an attempt to destroy it. However, doing such could result in creating a worse situation for ourselves. If we broke it into peices, the damage from multiple impacts could be just as bad as one big one.The other option is to do the best we can to prepare for such an impact. Those in the direct path of the impact would stand little chance of survival. however, if shelters areound the world were created to prepare for such an onslaught, with stockpiled food, water and resources – they may be able to hold out until the dust settled. The world they would be coming back out to would be far different than the one they left. With nearly every species and 75-90% of plant life possibly wiped out, humans would literally have to start all over.