Showing posts with label Siberia. Show all posts
Showing posts with label Siberia. Show all posts

Friday, February 15, 2013

Why Do Meteors Like Siberia So Much?

Earlier today a meteorite exploded over Siberia, near the city of Chelyabinsk. The meteorite, called a bolide, was captured on cell phones and video cameras by numerous observers, many of whom immediately uploaded their videos to YouTube.

The explosion caused an intense flash of light, a loud boom and a shock wave that broke windows over a large area. More than a thousand people were injured, mostly by broken glass caused by the explosion's shockwave, as they rushed to see what caused the flash.

The Chelyabinsk event calls to mind the Tunguska explosion of 1908. That meteorite flattened all the trees in 770 square-mile area. People have theorized all sorts of causes for the Tunguska incident, from mini black holes to alien spacecraft. But as the Chelyabinsk event shows, the most likely explanation is just a larger bolide, estimated to be 100 meters across.

So why do meteorites like Siberia? It's big. Siberia covers almost 10% of the earth's land surface. It's 77% of Russia's territory, and also includes parts of Kazakhstan, Mongolia and China.

It's estimated that the Chelyabinsk bolide was the size of an SUV, just a few tons. A bolide is a meteorite that explodes in the atmosphere with an apparent magnitude of -14 or brighter. Apparent magnitude is an astronomical term that describes the relative brightness of celestial objects. Magnitude is a logarithmic scale, and negative numbers are brighter. The sun as seen from Earth is about magnitude -27, or 400,000 times brighter than the full moon, which is almost magnitude -13. Planets like Venus and Jupiter are magnitude -4.89 and -2.94 at their brightest. The brightest star, Sirius, is magnitude -1.47, and the dimmest star visible to the human eye is about +6.50 under the best expected conditions.

Because there are nuclear weapons facilities nearby, there was initially some concern that the Chelyabinsk event was some kind of nuclear weapon. Russian news reports have repeatedly stated that "background radiation is normal."

YouTube, Facebook, Twitter and the Internet in general get a lot of heat for spreading rumors, misconceptions and lies across the world at the speed of light. But in this case cellphone technology and the Internet served to provide direct and immediate evidence of a natural cause for an event that in different times, say November, 1962 during the height of the Cuban missile crisis, could have sparked nuclear war.

The Chelyabinsk event comes on the same day that an asteroid, 2012 DA14, will pass within 17,000 miles of the earth (the two incidents are apparently unrelated). That's closer than geosynchronous communications satellites orbit the earth.

DA14 is estimated to be 45 meters across, or half the size of the Tunguska bolide. If it were to hit the earth, it would have the potential to kill thousands. But since most of the earth is covered by water, and a lot of the earth's land surface is empty like Siberia, the chances of a major death toll are low.

But the explosion over Chelyabinsk is a concrete reminder that the threat of asteroids and comets hitting the earth is not just science fiction. A relatively small asteroid could kick up enough dust and smoke into the atmosphere to start an ice age, as some scientists believe happened 2 million years ago. Sixty-six million years ago a bigger one hit the earth and wiped out the dinosaurs. At some point we will know that an asteroid or comet is going to hit the earth and we'll actually have enough time to do something about it.

And we should make sure we're ready. NASA has the Near Earth Observation program to track such objects and predict their paths. President Obama's plan for an asteroid mission is exactly the sort of thing we should be doing. And it's exactly the kind of thing you need a big government and international cooperation to do, because no business or single country should be held responsible for protecting the planet.

With all the arguments about the deficits and tax cuts everyone should take a step back. Some things are bigger than our petty squabbles about who really won a mandate in the last election. Instead of wasting all our energy on bickering we should start building things, going new places and making the world a better, safer place.