June 30th, 1908. Without warning, a massive explosion occurred over a remote area of Siberia. Tens of millions of trees flattened over an area of hundreds of square miles by a blast 1000 times that of the bombs that flattened Hiroshima and Nagasaki.
Earth had an encounter with a small asteroid or comet probably no more than 50 - 100 meters across. Heat from the blast was felt over 60km away. Fortunately, it hit a very sparsely populated area. Had it hit New York, London, Moscow, etc, the death toll could have been in the millions.
The object exploded in the air rather than staying intact until it hit the ground. Many smaller meteors will give into the stresses cause by passing through the atmosphere and explode before they hit the ground.
So what would we do if something like this was coming toward us today? Well, not much. However, the B612 Foundation is working on ways to deflect asteroids. This privately funded group wants to try to change the orbit of an asteroid by 2015 (being careful to select and asteroid that has no chance of threatening Earth after its orbit changes!)
All the techniques we are exploring to deflect asteroids require decades of advance warning. If we know about the threat that far in advance, we can make a small correction and decades later, it will miss us by thousands of miles.
The necessity of detecting these things in advance brings us to the current detection programs. Many programs currently exist to detect potential threats such as Spacewatch and Lincoln Near Earth Asteroid Research among others. Pan-Starrs and the Large Synoptic Survey Telescope will push the search to smaller objects.
There are no currently known asteroids that pose a threat. However, there is a potential one. Asteroid Apophis (about 300 meters across) will make a near approach to Earth in 2029 passing closer than our geostationary communication satellites. The odds of an impact in 2029 are exactly zero. We know it will miss.
But here's the catch. When it passes Earth, its orbit will change due to Earth's gravitational influence. There is a small area known as the "keyhole". If Apophis passes through this keyhole, it will come back and smack us in 2036. Fortunately, the keyhole is VERY small, only about 600 meters wide (and space is VERY big).
Just last week, the House of Representatives proposed a mission to study this asteroid (in HR6063, section 803). The proposal is for a low cost mission to place a transmitter on the asteroid. This transmitter would allow us to track its orbit much more precisely and tell us whether or not we really need to worry.
Impacts of this size happen probably once every 500-1000 years or so. On the 100th Anniversary of Tunguska, it's a good time to consider our preparations for the next one.
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Hale-Bopp, I have always found your posts to be fascinating. I wonder if you have any opinion on the end of the Great Cycle of the Mayan calendar in 2012 in relation to any kind of extraterrestrial event (i.e. an asteroid) happening then...
Just so you all know, I am exerting my telepathic powers to the fullest to prevent another meteorite from crashing into our planet.
Thank you, Madame Zoltar. I'm sure NASA appreciates your efforts.
I've been fascinated by the Tunguska event ever since I found out about it. Obviously, the people at the History Channel are, too, because they keep producing speculative specials about death raining down on us from the sky.
Also, I've always thought that the word "Tunguska" sounds like a toast you'd make when saluting friends: "Drink up! Here's to your health! Tunguska!"
Well, Orbs, my friend Phil Plait is going to add to that this fall when his new book Death From the Skie. He has assured me that, in addition to showing all the fun ways astronomy can do us in, he will also be sure to tell you just how unlikely any of them are.
Sylvia, I firmly believe that 2012 will go down in history as another year the world did not end. Yeah, I have survived way too many "Ends of the World" not to be a little flip about it by now :)
I haven't even heard a coherent picture from the doomsayers as to what is supposed to happen...I have heard asteroid impacts (none coming), some weird effect about the Sun, Earth and the Center of our Galaxy lining up (they never do that as the path of the Sun always passes north of Saggitarius A*, the center of our galaxy) to other odd ideas which don't always make sense.
So to end on a snarky note, I have a hard time taking the predictions of the Mayans seriously when they failed to see what the Spanish had in mind for them!
So what makes you think the Mayans DIDN'T know what havoc the Spaniards would wreak upon them? What could they have done to prevent it? Like those B612 guys - do ya really think they could deflect an asteroid?
All the big science guys - they don't seem to be doing so well with our little earthly basics like quakes & shifting plates & floods etc - I have to wonder what they could possibly do in outer space.
But thanks for your feedback and I agree - I have also survived many ends of the world and there will always be another coming. And I too am not sure what the doomsayers predict for 2012 - heard something about a major screw-up with gravity. I think I will try to think Mayan instead of Gregorian: it is layers upon layers upon layers... the number 2012 means nothing except starting over at zero.
And all the planets will continue to roll around.
Now one thing I neglected to mention in my original post is potential for us furthering the disaster. Let's say a major American or Russian city is heavily damaged. Will we take time to realize what has happened before or launch a retaliatory strike against a country that did not attack?
I hope we would be smart enough to figure out what happened, at least take some radiation measurements before doing anything rash ("we" should be construed to apply to whatever country was hit, be it the US, China, Russia, or any other country in the nuclear club).
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