Asteroid Threat

The Threat to Earth from Asteroids & Comets

Since it formed over 4.5 billion years ago, Earth has been hit many times by asteroids and comets whose orbits bring them into the inner solar system. These objects, collectively known as Near Earth Objects or NEOs, still pose a danger to Earth today. Depending on the size of the impacting object, such a collision can cause massive damage on local to global scales. There is no doubt that sometime in the future Earth wil suffer another cosmic impact; the only question is “when?”. There is strong scientific evidence that cosmic collisions have played a major role in the mass extinctions documented in Earth’s fossil record. That such cosmic collisions can still occur today was demonstrated graphically in 1994 when Comet Shoemaker-Levy 9 broke apart and 21 fragments, some as large as 2 km in diameter, crashed into the atmosphere of Jupiter. If these fragments had hit Earth instead, we would have suffered global catastrophes of the kind that inspire science fiction movies:

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Most of the asteroids and comets in our solar system pose no danger to our planet. But, for every thousand or so of those objects, there is one with an orbit crosses that of Earth, raising the possibility of a future collision. In 1991 the U.S. Congress directed NASA to conduct workshops on how potentially threatening asteroids could be detected, and how they could be deflected or destroyed. This mandate led to the Spaceguard Survey Report in 1992. In 1994 the House Committee on Science and Technology directed NASA, in coordination with the DOD, to work with the space agencies of other countries to identify and catalogue within 10 years the orbital characteristics of 90% of all comets and asteroids larger than 1 km and in orbits that cross the orbit of Earth.

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What can be done if one of these surveys finds an asteroid on a collision course with the Earth? Scientists and engineers at the B612 foundation are looking at ways of using a spacecraft to gently change the orbit of an asteroid. One promising approach is the “gravity tractor” invented by NASA astronauts Ed Lu and Stan Love.

One Response to “ Asteroid Threat ”


  1. Scientists seek ways to ward off killer asteroids

    A blue-ribbon panel of scientists is trying to determine the best way to detect and ward off any wandering space rocks that might be on a collision course with Earth. “We’re looking for the killer asteroid,” James Heasley, of the University of Hawaii’s Institute for Astronomy, recently told the committee that the National Academy of Sciences created at Congress’ request.

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