On Aug. 17 an asteroid estimated to be 17 to 39 meters in diameter will pass through space intersecting the Earth’s orbit, missing a collision by only about one million miles. The object will be moving at about 13,533 miles per hour, or 3.76 miles per second.
On Nov. 8, 2011 an asteroid between 360 feet and 800 feet in diameter will pass Earth’s orbit, missing a planetary collision by a mere 200,000 miles. This huge mass of stellar debris will float by Earth about 80 percent closer than the Moon, and the impact of such an object would be expected to produce have disastrous effects.
As of October 2008, scientists at NASA have detected 982 of the near-Earth objects that are at least one kilometer wide, although it was estimated that almost 200 of the potentially dangerous asteroids and comets have not yet been found. Near-Earth Objects (NEOs) are comets and asteroids that have been nudged by the gravitational attraction of nearby planets into orbits that allow them to pass close to the Earth’s vicinity.
Although comets and asteroids may well have delivered the water and carbon-based molecules to the Earth’s surface – thus providing the building blocks of life itself – these giant space rocks would cause a global catastrophe if one were to strike our planet today.
It now seems likely that a comet or asteroid struck near the Yucatan peninsula in Mexico some 65 million years ago and caused the extinction of more than 75 percent of the Earth’s living organisms, including the dinosaurs.
Fortunately, anything from space that actually impacts with the Earth is likely to be so small that it would disintegrate in the atmosphere and not cause harm on the ground. On a daily basis, about one hundred tons of interplanetary material harmlessly drifts down to the Earth’s surface.
The threat to any one person from auto accidents, disease, other natural disasters and a variety of other problems is much higher than the risk posed by an asteroid or comet.
Still, the potential harm has earned some attention in Washington DC. In 1998, Congress ordered NASA to identify near-Earth objects larger than one kilometer across and in 2005, that mission was extended to smaller objects, 140 meters across, which can wreak regional havoc.
A wealth of information about these nearby comets and asteroids may be found online at http://neo.jpl.nasa.gov/neo/
NASA discovery data through Aug.14, 2011 shows that 8,080 near-Earth asteroids and comets have been found but fewer than 1,000 of them have diameters roughly one kilometer and larger. Space agency scientists have been directed to scan the heavens for potential problems until 2020.
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