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.
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.
Observations by astronomers tracking near-Earth asteroids have raised a new object to the top of the Earth-threat list.
A NASA-led search for Earth-threatening asteroids as small as 140 metres has been approved by the US Congress and is awaiting President George W Bush's signature. The bill provides no money, but survey telescopes are already in development.
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.