As they say, truth is stranger than fiction.
On December 26, 2004, the Asia-Pacific region was hit by a giant tsunami, triggered by a massive earthquake that struck and wreaked havoc in Indonesia’s Aceh. While the world was grappling with the overwhelming disaster, astronomers were busy assessing the probable impact of an asteroid that could unleash devastation of an even bigger magnitude.
While the probability of impact of asteroid ‘2004 MN4’ (rechristened ‘99942 Apophis’) on April 13, 2029 (Friday the 13th) was later ruled out, what no one could conclusively say during the tense days of December 2004 whether it would miss Earth on that day.
2004 MN4 was first located on June 19, 2004 by Roy Tucker, David Tholen and Fabrizio Bernardi from Kitt Peak, Arizona. They observed it for two nights but then lost it. The same year, six months later, Gordon Garradd of the Siding Spring Survey in Australia rediscovered it on December 18.
Following detailed observations, scientists came to the conclusion that the asteroid was capable of hitting our planet. With a diameter of about half a kilometer (later revised to about 400 metres), the asteroid had the capability of causing extensive regional damage around the area of impact, if it did hit Earth.
Astronomers concluded that the predicted flyby of 2004 MN4 on April 13, 2029 would be too close for comfort.
Consider this: Geosynchronous satellites orbit at 22,300 miles (36,000 km). On April 13, 2029, asteroid 2004 MN4 will fly past Earth only at 18,600 miles (30,000 km).
After detailed observations, on December 23, astronomers said that the asteroid had a 1-in-233 chance of hitting Earth in April 2029. On the Torino scale (much like the Richter scale for earthquakes), it got a rating of 2 – a slight chance of impact.
Prior to the discovery of 2004 MN4, whenever scientists have predicted a Near Earth Asteroid (NEA) hitting the Earth, refined analyses have always downgraded the possibility of impact, lowering the Torino Scale rating to 0.
However, in the case of 2004 MN4, the rating was upgraded to 4, with a 1-in-60 chance of impact, on December 24. Just two days later, on December 26, that probability was quietly upped to 1-in-37.
The Torino 4 rating implies a 97% chance of missing the Earth, but it still is the highest ever rating given to any NEA.
Though astronomers, after further refined studies, have noted that 2004 MN4 will miss the Earth in April 2029 by a few tens of thousands of miles (not much distance in space context) in an eye-popping close encounter, appearing at the closest approach as a shining 3rd magnitude star, visible to the naked eye from Africa, Europe and Asia (also in cities despite hazy cover), the final impact ratings could wobble in 2029 like in 2004.
In recorded history, no other asteroid of this size has been seen with the naked eye.
Uncertainties are always associated with near-Earth objects in space, so the possibility of an impact cannot be entirely ruled out.
If not in April 2029, a possible impact on April 13, 2036, is still a probability. Astronomers have maintained the rating at level 1 on the Torino scale for April 2036, with an estimated impact-probability of 1 in 5,560.
However, that rating could drastically alter following the approach in 2029. Till that flyby, it is difficult to make exact predictions. There is speculation that the asteroid might swing around and hit the Earth after all.