The first person I saw on Friday morning said, "Hey, did you hear an asteroid hit Russia this morning? It's all over Twitter."
Now, this immediately raised a bunch of red flags for me. I knew, of course, that a 50-metre-wide asteroid, specifically 2012-DA14, was going to buzz the Earth at an incredibly close 27,500 kilometres at approximately 1 p.m. Saskatchewan time. I also knew there was no chance it was going to hit us, so this news smacked of a hoax.
What were the chances of a totally unrelated impact of an asteroid we didn't know about happening in such close time proximity to one we did know was going to be in the neighbourhood?
I knew the likelihood had to be-you will forgive me-astronomically low even though the planet is constantly under bombardment from near-Earth objects (NEO). Scientists estimate approximately 100 tons of space debris, mostly dust and sand sized particles, enters the atmosphere every day. Most of it burns up, and given the planet is about 70 per cent covered by ocean, even the smaller ones that do make it to the surface are not found all that frequently.
I quickly fired up my Internet browser and, as it turns out, a fairly large object, about 15 to 17 metres across had exploded approximately 15 to 25 kilometres above the Ural Mountains near city of Chelyabinsk, Russia. The energy of the explosion was about 500 kilotons or close to 33 times the magnitude of the atomic bomb that leveled Hiroshima, Japan at the end of World War II.
The resultant shock wave from the blast knocked out windows in 3,700 buildings causing thousands of injuries.
A NASA spokesperson said an event like this probably occurs every 100 years, or so, on average. The last-known similar impact also hit Russia. In 1908, an object known as the Tunguska comet, exploded over a remote area in Siberia leveling more than 2,000 square kilometres of forest.
Tunguska would have been more similar in size to 2012-DA14 and there is some debate as to whether it was actually a comet. Also, contrary to the reports I was initially given, the Chelyabinsk object was not an asteroid.
Perhaps a quick primer on NEOs is in order.
Comets are large bodies of rock and ice. As such they project an aura and long tail as they approach the sun and the volatile ice is melted.
Asteroids are large bodies of rock and metal.
Meteoroids are smaller bodies of rock and metal.
There is no hard and fast rule of where the demarcation is between asteroids and meteoroids, but generally speaking Chelyabinsk-sized objects are meteoroids. When they streak through the atmosphere they are referred to as meteors and any chunks that hit the ground become meteorites.
So, getting back to the likelihood of a near miss of a 2012-DA14-sized object combined with the impact of a Chelyabinsk-sized object at virtually the same time, the math is fairly straightforward.
Scientists now estimate asteroids pass within Earth's orbit every decade or two. If a Chelyabinsk event occurs every hundred years the probability of both happening on the same day is (100 years times 365 days) times (10 years times 365 days) or 36,500 X 3,650. Most news stories called the odds 100 million to one. My own calculation is more like 266 million to one, but I'm not going to quibble, let's just say, statistics show it is highly improbable.
And yet it happened. Then again, the odds of winning the world's biggest lotteries are on the same scale, but people do win.
Adding intrigue to this story, at least for me, was a recent study published in the scientific journal Tectonophysics of a terrain in Australia that shows evidence of what would be the third largest impact crater ever discovered.
Researchers suggest the structure of the East Warburton Basin indicates an asteroid approximately 20 kilometres across hit the Earth 360 million years ago corresponding with the time of one of the great mass extinction events in history.
Far be it from me to fuel the fire for doomsday forecasters (who am I kidding, I love tweaking them) but truly catastrophic impacts have happened in the past and will inevitably happen again.
NASA is currently tracking nearly 1,000 NEOs more than a kilometre wide.
Although none of these currently pose any threat to Earth, a NASA report last year estimated only 20 to 30 per cent of what they call "potentially hazardous asteroids" have been found.
Even legitimate astronomers believe NASA should be doing more to identify possible threats.
The end is not nigh, but it is definitely possible, astronomically improbable, but possible nonetheless.
