Near-Earth Objects (NEOs) are comets and asteroids in heliocentric orbits that have been influenced by planetary flybys causing them to approach Earth. Comets are composed mostly of water ice and dust particles that were formed in the cold outer planet system.
Most of the rocky asteroids were formed in the warmer inner solar system between the orbits of Mars and Earth. There is a great deal of scientific interest in NEOs because they are the unchanged remnant debris from the solar system formation process of some 4.6 billion years ago.
In addition, there is growing fear that a large asteroid will hit Earth and wipe out all or part of the world’s population and habitation. Such asteroids come in all sizes and are the product of the initial agglomeration of the inner planets including Mercury, Venus Earth and Mars.
Predictions of possible large Neo-Earth encounters are occasionally announced, but there have been no recent life-threatening large asteroid collisions with Earth. Nevertheless, often pieces of natural space rocks such as shards of comets or asteroids do survive the Earth’s atmosphere and strike the ground.
In fact, thousands of tiny pieces of space rock, called meteorites, do hit the ground annually. Most of these events are unpredictable and go unnoticed.
The last recorded hit of a noticeable meteor was in February 2013. With an estimated mass of about 10 tons and over 50 feet wide, the Chelyabinsk Asteroid streaked across the sky above Russia’s Ural Mountains and exploded with the power of an atomic bomb.
About 1,100 people were injured from shattered windows, an after effect of the sonic boom. Because such objects come from heliocentric orbits their speed at encounter is typically around 33,000 mph. Atmospheric encounters at these speeds usually result in break ups at altitudes of 18 to 32 miles.
Earlier this month astronomers from the Czech Academy of Science claim they have evidence that Earth is at constant risk of asteroid collisions. They discovered that the Taurid Stream could catapult a 1000-foot wide asteroid into the earth’s oceans or land masses. A meteor strike of this size could wipe out entire regions if it hits.
The frequency of meteor showers is high during the months of October and November when Earth passes the Taurid stream of asteroids. Czech observations indicated two large rock formations measuring 650 feet and 980 feet wide. These scientists reported the risk of large asteroid collisions with earth increases annually as the planet passes through the Taurid Stream.
The impact of a 1000-foot meteor would be so great that it would be impossible to slow it down by natural causes. The impact would vaporize the space rock and throw all the crumbled rocks from the Earth’s mantle into the air. Some rocks would even speed into space while most would spread around the planet.
A common question is: What can we do if such an event is ever predicted with accuracy? There is no clear and simple answer. Any decision to do anything would depend on the expected size and mass of the meteor, how much notice is given in terms of time and an assessment of the options at hand.
As of today, we have few, if any, options that might work. The program and funds needed to prepare for such an event would be huge, while the odds of such a possible catastrophe occurring in any given time frame are very low. In summary, the cost-risk ratio is very high, discouraging the needed investment and maintenance costs of a planetary defense system.