A Rogue Asteroid - Totally Unavoidable
By Kevin Roeten (12/01/07)
The majority of citizens know it’ll happen, but not when. And it won't be by man’s hands. With missile defense, multiple nuclear strikes by any nation look unfeasible. But few realize what one asteroid can do. Many say chances are minute, but how does one define minute?
History, actual chances, and sheer numbers of asteroids should convince anyone that if the world will end, this is likely how it’s going to happen. If one looks at the known objects orbiting the sun, just within the orbit of Mars [cfa-www.harvard.edu/iau/lists/InnerPlot.html], they will see a virtual “cloud” of objects(asteroids).
To date there is 907 Potentially Hazardous Asteroids(PHAs) that exist in that cloud[SpaceWeather.com]. PHAs are space rocks larger than 100 meters that can, or will, cross the path of earth’s orbit around the sun. But that number will be skewed upward by a close pass to earth that may affect any asteroid’s trajectory by gravitational pull. Approximately six additional PHAs are discovered each month.
Every known Near Earth Asteroid(NEA) has been tracked for years to come. Programs such as NEAT, SpaceWatch, LONEOS, NEOP, and LINEAR are watching for any rogue asteroids. NASA has taken up the search for NEAs, and knows that less than 10% of the estimated 2,000 asteroids(larger than ½ mile diameter) have been detected.
Author Michael H. Brown reveals that any asteroid greater than ½ mile in width upon impact would kick up enough dust to possibly blot out sunshine for months. An estimated 1 out of every 6 would die from crop shortages and malnutrition. An object a mere 200 yards in diameter (~17,000 mph) could cause destruction equivalent to 650 Hiroshimas.
We’ve been targeted by asteroids before. An impact site, off the coast of the Yucatan Peninsula in Mexico, occurred 65 million years go. It eliminated the dinosaurs, and 75% of all species. In 1490 in China’s Shanxi Province (NASA), 10,000 people were said to have been killed by a hail of falling stones(breakup of large asteroid). How about Arizona’s Meteor Crater(Flagstaff)? In 1908 an asteroid less than 100 yards in diameter sent a shock wave that struck Tunguska(Siberia), felling an estimated 80 million trees for 830 square miles.
The late Eugene Shoemaker(US Geological Survey) estimated that the rate of earth impacts and events the size of the Hiroshima blast occurs about once a year. These events generally go unnoticed because most of the earth is covered by water and a good portion of the land surface is uninhabited. The explosions generally occur at a relatively high altitude with a huge flash and thunderclap, but no real damage. Early warning satellites have picked up 136 major explosions(1975-1992) in the upper atmosphere. The 1994 impact of Comet Shoemaker-Levy 9 with Jupiter was a major ‘wake-up’ call.
On 5/19/96 a 400 meter asteroid(1997JA1) passed within 720,000 miles of earth--detected only a few days before. On 3/18/04 a 30 meter asteroid (2004FH) passed within 64,000 miles of earth(~6 earth diameters). This was known only a few days after it had been detected. On 3/31/04 a 6 meter asteroid (2004FU162) made the closest pass ever observed. Without warning, the asteroid sped within 10,000 miles(one earth radius).
On 7/09/02 a 1.2 mile wide asteroid was detected by NASA. Designated as 2002NT7(Astronomy), a small chance of a collision with earth on 2/1/19 was indicated. NASA later released a statement that with 2002NT7 earth impact possibilities would not occur, but they could not rule out an impact when it returned on 2/1/60.
On 3/12/98, CNN reported that mile-wide asteroid(1997XF11) may be on a course for collision in 2028. This asteroid was discovered by Jim Scotti(SpaceWatch). Further observations revealed that 1997XF11 should miss the earth by just under 30,000 miles on 10/26/28. However, the margin of error is 180,000 miles. An asteroid the size of 1997XF11 would equal almost 2 million Hiroshima bombs. By water, it would create a tidal wave hundreds of feet high, or by land blast a crater 20 miles across.
But in 2004, a newly discovered 320 meter Apophis was given the highest impact probability(4/13/29) ever---1 in 17 by Steve Chesley(Jet Propulsion Laboratory). Later observations(11/23/07) showed that the asteroid will miss the earth by ~21,000 miles(within orbits of communications satellites).
Interestingly, NASA admits that its orbit will be altered unpredictably (earth’s gravitational pull) in a way that does not rule out a collision on 3/36, or later in the century. One has to wonder how earth will alter other PHAs, what PHAs are circling the sun with a preset date of impact, or how many PHAs are undetected as of yet.
[“2001 Space Odyssey”]Arthur C. Clarke’s The Hammer of God may put things more into perspective. Of course, nothing is known for sure. But that’s the real scary part.
Kevin Roeten
http://kevinroeten.us/
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