It was a 2 km wide asteroid. And it was headed for the Earth, with collision predicted for February 1, 2019. The asteroid is in orbit of 837 days around our sun. From the time it was discovered by MIT’s near earth asteroid research project in 2002, visions of Armageddon had been painted by imaginative commentators.

If an object of that size hits the earth, it may wipe out around 1.5 billion people and most of the bigger animals, conjuring up the worst doomsday scenario of the movie Deep Impact. The secondary impact over the years may bring about more devastation. Although the chance of such an asteroid hitting the Earth one in a million year, the latest recalculation has made the threat miniscule.

But can a devasting impact of an asteroid happen during our lifetime, and can we detect it accurately?

The solar system is awash in near earth objects, including comets and asteroids. Composed mostly of water ice with embedded dust particles, comets originally formed in the cold outer planetary system while most of the rocky asteroids formed in the warmer inner solar system, between the orbits of Mars and Jupiter. They are often nudged by the gravitational forces of the planets or the sun on to a collision path with the Earth.

On October 8, a 10-metre asteroid ended up in the atmosphere above Indonesia’s island region as a fireball blast with the energy of 50 kilotonnes. The event was recorded, but there was no loss of life. The nuclear bomb that the US dropped on Hiroshima had a 15-kilotonne yield.

There are countless tonnes of space dust, millions of meteors, asteroids, comets and various types and sizes of debris flying around in space at incredible speeds. Objects the size of a basketball hits the Earth every day – it just doesn't show up on the common man's radar because the impact isn't newsworthy.

The last time the rest of us really noticed something hitting the planet was in 1908 called the ‘Tunguska’ impact, when an asteroid about the size of a football field exploded in the Earth's atmosphere with the force of a 10-megaton bomb, leveling an 2,000-sq-km area of Siberia, big enough to engulf a city the size of New York.

Worried by the catastrophic impact of a large hit, the US Congress had asked Nasa to set up a near earth object programme in 1998. The aim was to to identify asteroids or comets that could be potentially hazardous to the Earth. The programme goes through the painstaking process of naming every object, big or small which could threaten earth.

But an interagency committee set up by the US government in December last year, to look at possible responses to a big threat, found that no agency was really prepared. It also said that scenarios of deflecting a big object with nuclear explosion were unlikely to work, since it needed a lead time of at least three decades to react. And most of the objects were discovered only a few years away. Some as little as three days.

Peter Brown of the University of Western Ontario looked at the data of eight years and found 300 in-air explosions of space rocks ranging in size from large television sets to studio apartments. But his analysis also revised downwards the statistical probability of Tunguska-size impact from once every hundred years to once every thousand years. He found one-hundred years to be the likely interval between impacts one-tenth the Tunguska-size, or of one megatonne since — six times the force of Hiroshima.

Considering the last one to happen in 1908, statistically speaking, we may be due for a collision any time now. An asteroid named ‘Apophis’ caused a brief period of concern in December 2004, because initial observations indicated a small probability of up to 2.7% that it would strike the Earth in 2029. In 2005, scientists calculated that Apophis had a one in 5,500 chance of colliding with Earth. As of October 7 this year, the impact probability has decreased considerably to a 1 in 250,000.

The near earth object programme requires Nasa’s equipment to be able to locate and identify at least 90 percent of objects one km in diameter or larger. Nasa has since successfully achieved the desired track rate, but the problem is that a National Research Committee report says we shouldn't be satisfied with this. Asteroids smaller than 1 km in diameter are not less disastrous to humanity. For example, the one that caused the 1908 Tunguska explosion was only 30 to 40 metres in diameter. Nasa has now been asked to track 90 percent of objects 140 meters or larger by 2020.

Although the new goal has been formulated, neither Congress volunteered funding for the goals nor has Nasa allotted any money from its budget. As a result, if a Tunguska-sized body were headed for the Earth today, its arrival would probably be a complete surprise. Of course, Tunguska is the only collision recorded in history, suggesting that threatening bodies that cross planet Earth’s path are rare. Considering this, and the fact that the most disastrous varieties of asteroids are fairly well covered, danger is probably not imminent but still could be a possibility.

On November 4, 2008, a small near-earth asteroid exploded upon atmospheric entry above Northern Sudan. No damage was done but the fireball explosion was unique in that Nasa technology was only able to predict the location and time of impact a day before the actual event. For the near earth objects program to move forward towards its latest goal, Congress would have to pay up and hope that no big object was headed for our home we call the Earth.

The writer is a doctoral scholar, Carnegie Mellon University, Pittsburgh and knowledge editor at Financial Chronicle