A Planet Under Siege

The spectacular meteor which assaulted the lower Ural Mountains in Russia last Friday has sparked a variety of thoughts.  It was the most dramatic event involving a meteor which I can remember occurring in my lifetime, although meteorites falling to Earth are extremely common and the large air bursts which can sometimes occur as a result generally happen every few years or so.

Residents in the area, most concentrated in the city of Chelyabinsk, were having a normal day on Friday morning, the 15th February.  Then the skies lit up in a dazzling burst of light which I believe briefly outshone the sun, and was comparable to the light emitted by nuclear explosions.  This fireball danced across the sky leaving a trail of large, white clouds.  This alone, while spectacular, would not have been anything hugely significant – I’ve seen similar meteors in my life, albeit nowhere near so bright.

It was the following air burst which would make international news worldwide.  Rather than read any flawed description I could come up with, simply watch the beginning of this video:

The effects were catastrophic.  Windows in over 300 buildings were shattered, doors blown open, alarms all over set off into a frenzy.  The roof of a zinc factory collapsed.  Over 1,000 people were injured, mostly from glass – many people would have been staring in awe through windows at the meteor at the time.  Mercifully nobody was killed by the meteor.  It is thought that this explosion had over 20 times more power than the Hiroshima atomic bomb.

In some bizarre cosmic idea of a joke, a separate meteor, the 2012 DA14, was already that day scheduled to pass closer to the Earth than had ever been recorded to pass before on the.  Although astronomers had ruled out any possibility of impact and, indeed, we’re all still here today, it was a terrifying coincidence and did make me feel as if the Earth were under siege that day.  I read a figure which stated that, if 2012 DA14 had showed up 15 minutes earlier, there’d currently be city-sized devastation somewhere in Southeast Asia.

But of course, we are always under siege.  Due to our atmosphere and erosion on the planet’s surface it may not be immediately clear, but many, many meteors have struck the planet before.  Most noticeable is the originally named Meteor Crater in Arizona, which has stayed preserved for tens of thousands of years.   There are so many chunks of rock and material orbiting the Sun which could wipe us out.  You might think that by now the solar system would have sorted itself out and would exist in harmony, but meteors are constantly changing orbits.  Just passing the Earth changed 2012 Da14’s orbit by something like 50 days.

“We’ve been okay up until now, so why would anything change?”
This is something I often think to calm fears of an impending catastrophe.  Then I remember how it is commonly accepted that a meteor was responsible for the extinction of the dinosaurs, along with over half of all life on our planet.  Okay, that was 60 million years ago, but that is nothing when considering our planet is over 4 billion years old and multicellular life has existed for over 1 billion years.  Civilisation and humanity could easily be wiped out by a similar impact.

There’s even been dramatic occurrences within human history.  Russia seems particularly vulnerable to meteor attacks; I’m sure you will have heard of the Tunguska event, which happened in 1908.  Due to a lacking scientific presence in Russia at the time and the ensuing chaos of the First World War and the Russian Revolution and Civil War, no extensive study could be carried out until 1927.  What we do know was there was a massive explosion which is thought to have destroyed over 80 million trees over an area of 2,000 square kilometres.  Siberia was and still is a very sparsely inhabited place and so only one death was recorded.  Imagine the implications if a similar explosion had happened over London, Berlin or Moscow.  There could have been millions of casualties – history could have gone in a completely different direction.   We have never been safe.

Good news: astronomers believe they have accounted for about 98% of all asteroids capable of inflicting such damage.

Bad news: smaller asteroids capable of destroying cities are less well charted.  We might not even be aware of one until it sneaks up on us.

So, if we were to discover that an asteroid has turned kamikaze and wishes to wreak destruction upon our planet, what can be done?  There is the obvious idea – bomb it!  Despite being a modern answer to everything, bombing a meteor would be very risky because we simply have no idea what would happen.  Would the meteor fragment, or, since we may not know what the meteor is comprised of, could it be tough enough to stick together?  Would it break into smaller pieces and cause similar destruction anyway?  What would happen to its velocity – and therefore its potential energy?  We would also have to get over an international ban on the presence of nuclear weapons in space, which would be a diplomatic nightmare even with the face of imminent catastrophe.

Other options range from sticking a rocket onto an asteroid to change its orbit and thus deflect it from the Earth, to painting it white in order for the Sun’s rays to effect the orbit.

In other words, humanity has no effective plans in place to react to the discovery of a deadly asteroid.  Until we do, which I do not see as being very likely in the near future, our reaction to the discovery of an asteroid may simply be to avacuate the area at risk of being hit and to prepare for a catastrophic humanitarian disaster.  Until we develop efficient means of deflecting asteroids, this is a good as it gets.

Scientists don’t believe any large asteroids will pose a threat to us for a very long time.  Smaller ones, however, are very possible.  The highest near-future risk is the 2007 VK184, which currently has a 1 in 1,820 chance of colliding with the Earth in 2048.  However it is due to pass the Earth (at a safe distance) in just over a year’s time during May 2014, giving  us the chance to observe it and determine more accurately the threat it will pose.  Chances are we will then be able to rule out a collision.  However, there will certainly be future meteors hitting the Earth.  I expect to see several more events similar to those in Russia within my lifetime.

The Pope chose a really bad week to resign.

Useful link: http://www.aljazeera.com/indepth/opinion/2013/02/201321212834710672.html

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