A newly discovered asteroid is now the biggest thing known with a possibility of hitting the Earth in this century—and it is also the one that could hit the soonest.

But the odds of impact currently stand at just one in six million, reducing the fear factor somewhat, and these odds should further diminish with additional observations. This latest addition to NASA-JPL's list of potentially hazardous asteroids was discovered on 27 April 2006.

The asteroid, called 2006 HZ51, has an estimated diameter of about 800 metres and is the one of the largest objects ever to make the list. An object of that size would cause widespread devastation if it did strike the Earth.

HZ51 also has one of the shortest lead times to a potential impact of any such object yet found, and the shortest of any potential Earth-impactor currently on the list. The earliest of its 165 possible impact dates is just over two years away, on 21 June 2008

Hollywood Movies

Dan Durda, an asteroid expert and president of the B612 Foundation—which aims to anticipate and prevent such impacts—thinks the discovery of HZ51 highlights that at present there are no good options when faced with so little time to prepare. "There really isn't a whole lot we could do," he told New Scientist. "Most of the options that don't resemble a Hollywood movie involve deflection techniques that require many years or decades."

Other than stockpiling food and supplies and evacuating the regions most likely to be affected, he said, we would have to "hunker down and take the impact."

But this is an unusual case, statistically speaking. It is far more likely that Earth's nations would benefit from a much greater lead time before a potential impact, allowing more time for planning.

For example, the second-most imminent threat now on the list is the asteroid Apophis, which has about a 1in 6,000 chance of hitting Earth in 2036—plenty of time to prevent it.

Altering Orbits

The B612 Foundation has been pushing for a mission to place a tracking device on Apophis sometime in the next decade, so that the possibility of impact can be definitively proved or ruled out. The foundation also wants to send a mission to test ways of altering the orbit of a nonthreatening asteroid, to test the viability of such methods.

But the chance of an impact by Apophis might be ruled out as early as this weekend, which will be the last chance until 2013 to observe it by radar, from the Arecibo radio telescope in Puerto Rico.

Whilst none of the above headlines saw the light of print because they would have been ridiculed for being too sensationalistic, they would in reality be no less alarmist than the presentation of some of the other news topics.

The media usually fails to highlight this natural phenomenon, quite rightly pointing out that we have enough on our plates without adding additional concerns about terror from space. And yet, the facts are as real, and the chances no slimmer, than some of the news that bombards us daily.

Instead, headlines about (in some cases) longer odds of "personal danger" capture prime news slots: bird flu, dirty-bomb threats, AIDS, cancer caused by second-hand smoke, eating too many burgers, the risks of not wearing seatbelts, drinking unboiled water, excessive anything.

You name it, we have covered and analysed how these things can kill us, and yet mention of having one's city wiped out in a split second by a giant meteorite is immediately fobbed off as "slim, an outside chance, and improbable."

Why Are Asteroids Such Low-Key News Items?

We do it in spades when it comes to earthbound threats. The news is full of scary topics, most of which have even slimmer chances of harming the average individual.

It's not just the media; it's the authorities who keep this threat on a back burner, or prioritise other threats, for instance ...

If an intelligence agency had a tip of a nuclear terrorist attack, down to the actual date and time two years hence (and it were known that there might be others), one doubts whether it would face budget restrictions in hunting for them.

If seismologists could give Los Angles an exact date of a catastrophic earthquake, how many billions would be spent on research/preventive measures?

The list of examples and similarities could go on, but the point has been made: we differentiate between matters above and below the ozone layer. Perhaps it's time we didn't.

The fact that an object as large as 800 meters and as close as two years away, with the potential to change the world as we know it, was only found in May 2006 also didn't seem to attract any attention.

Obviously we are still a long way from even knowing where all the big asteroids are, not to mention smaller ones less than 100 meters wide, which "only" carry the devastating powers of multi-mega-nuclear proportions. Clearly our "early-warning system" is far from adequate.