Scientists Discuss Asteroid Threat to Earth

Deccan Chronicle September 24, 2007
By Syed Akbar
Hyderabad, Sept 23: The discussion on how to prevent potentially dangerous asteroids from hitting the earth will be the highlight of the week-long 58th international astronautical congress which begins here on Monday.
Astronauts from around the world will discuss and chalk out a strategy on earth-threatening asteroids, some of which may collide with the human planet in the next few decades leaving a trail of death and destruction. The Hyderabad congress will serve as a platform for internationally renowned astronauts to discuss the results presented at the 2007 Planetary Defence Conference held in March in Washington DC.
They will also discuss a range of possible options for deflecting a threatening object and outline opportunities for future research on the nature of asteroids and comets.
The 2036 close approach of the asteroid Apohis, which is currently predicted to have a one in 45,000 change of impacting the earth, will be highlighted at the conference as an example.
During its close passage by the Earth on April 13, 2029, it is possible that asteroid Apophis will pass through a keyhole leading to a collision in 2036.
The meeting will also highlight areas where the international community needs to work together to resolve current political, policy, legal, and other non-technical issues related to asteroid deflection and impact disaster mitigation.
According to an estimation by the National Aeronautics and Space Administration, an impact from Apophis would release more than one lakh times the energy released in the nuclear blast over Hiroshima.
"Thousands of square kilometres would be directly affected by the blast but the whole of the earth would see the effects of the dust released into the atmosphere," NASA scientists points out.
NASA has suggested two possible methods of protecting the earth from an asteroid or comet determined to be on a collision course, by destroying the object before it hits the earth or by deflecting the object from its orbit before it hits the earth.
To destroy the earth-approaching object, astronauts would land a spacecraft on the surface of the object and use drills to bury nuclear bombs deep below its surface. Once the astronauts were a safe distance away, the bomb would be detonated, blowing the object to pieces. Drawbacks to this approach include the difficulty and danger of the mission itself, and the fact that many of the resulting asteroid fragments might still hit the Earth, resulting in massive damage and loss of life.
In the deflection approach, powerful nuclear bombs would be exploded up to half a mile away from the object. The radiation created by the blast would cause a thin layer of object on the side nearest the explosion to vaporise and fly into space. The force of this material blasting into space would recoil the object in the opposite direction just enough to alter its orbit, causing it to miss the earth.
NASA now supports, in collaboration with the United States Air Force, the Spaceguard Survey and its goal of discovering and tracking 90 per cent of the Near Earth Asteroids with a diameter greater than about one kilometre by next year.