A study by NASA's Jet Propulsion Laboratory shows that the weak gravitational pull of a nearby spacecraft could deflect a hypothetical asteroid 140 meters across, big enough to cause regional devastation if it hit Earth.

A group of scientists, joined by a member of Congress, used the 100th anniversary of the Tunguska asteroid event this week to draw attention to their belief that the United States is not doing enough to defend the planet against the dangers posed by near-Earth objects.

In recently passed H.R.6063, The U.S. House of Representatives would direct the NASA Administrator to develop plans for a low-cost space mission to rendezvous with the Apophis asteroid and attach a tracking device.

A Canadian satellite, the Near Earth Object Surveillance Satellite, is designed specifically as an early warning system to pinpoint asteroids on a collision course with Earth. It will also detect space junk in the path of other orbiting satellites to prevent crashes that could shut down telecommunications - television, telephone, GPS and banking systems - around the globe.

As if forecasting whether asteroids will hit the Earth wasn't hard enough, it now seems that primordial black holes could surprise us by nudging a rock or two our way.

An asteroid hurtling towards Mars has a 1 in 28 chance of walloping the Red Planet on 30 January, according to the latest calculations. The rock's discovery just a couple of months before a possible impact begs the question of what would happen if it were instead headed for Earth.

By the end of this year, NASA hopes to find about 90% of the largest asteroids that could potentially strike Earth, a blast that could throw dust into the atmosphere and cause firestorms and acid rain. These asteroids can be as large as mountains but are at least 1 kilometer (3,280.8 feet) in diameter. NASA estimates that 900 of these objects are in potentially hazardous range of Earth.

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.

NASA officials say the space agency is capable of finding nearly all the asteroids that might pose a devastating hit to Earth, but there isn't enough money to pay for the task so it won't get done.