The fact that a relatively small asteroid could still cause such a massive explosion as Tunguska suggests "we should be making more efforts at detecting the smaller ones than we have till now," according to astronomers.

Last week two events in Washington - a conference on "planetary defense" held by the American Institute of Aeronautics and Astronautics, and the release by NASA of a report titled "Near-Earth Object Survey and Deflection Analysis of Alternatives" - gave us good news and bad on this front. On the promising side, scientists have a good grasp of the risks of a cosmic fender-bender, and have several ideas that could potentially stave off disaster. Unfortunately, the government doesn't seem to have any plan to put this expertise into action.

A gravity tractor, as envisioned by scientists, is a spacecraft that would hover over an asteroid on a collision course with Earth and, through gravitational attraction, accelerate or slow down the asteroid's rate of travel. By altering the speed, the gravity tractor could prevent the asteroid from striking Earth and wreaking environmental and economic havoc.

A pair of NASA astronauts has unveiled a design for an innovative space tug that could one day save the world by nudging a potentially threating asteroid out of the Earth's path.

British scientists are undertaking a three-year, £300,000 government study to work out the feasibility of changing the direction of threatening asteroids.

The creation of a government agency to protect the Earth from a catastrophic asteroid strike is being endorsed by a senior member of the U.S. House Science Committee.

A team of researchers have come up with an asteroid defense concept that would use a swarm of nuclear-powered robots to drill into an approaching asteroid and hurl chunks of it into space with enough force to gradually push it into a non-Earth impacting course.

An international group of astronomers and policymakers met to discuss possible next steps to defend Earth against asteroids.

A cadre of space scientists is becoming more adept at sorting out the swarm of asteroids and comets floating through the solar system and has turned its attention to the more-daunting job of doing something about the potentially disastrous collision with Earth.

NASA researchers are developing methods to nudge Earth-bound asteroids out of the way.