Jupiter was hit by a comet that has left a scar the size of Earth.

http://www.foxnews.com/story/0,2933,535090,00.html

This type of thing is a real risk for Earth.  Barely 100 years ago something hit this planet with the force of a nuclear bomb that had it struck a populated area would have devastating and could have killed millions.  Fortunately, it just hit remote Siberia. 

If an object hit Earth like the one that just hit Jupiter the result would likely eliminate human life on Earth.  We need to invest more resources in countering this threat to the entire planet.  If we detected an object early, far away from Earth, there are a variety of comparatively easy means to alter its course only slightly and shift it away from us.  But trying to do so late in the game, when the impact is closer, would require much larger efforts to shift its course and could well be beyond our capabilities.  Thus, early detection and the capability for deep space interdiction may be necessary for the survival of the species.

 

"A man never drinks anything that a plant lives in" --DBone (A Real Man).
http://vimeo.com/4938173

The threat is far greater than most know or perhaps wish to know.

Jupiter, and the other gas giants in our outer solar system act as giant vacuum cleaners that help protect the earth and all the inner terrestrial planets. The gravity from the gas giants in our solar system, of which Jupiter is the largest, provides us with a kind force field by attracting the many chunks of rock, ice, and metal that fly into our solar system.

However there are enough that make it by that we are in constant danger of a catastrophic impact. And then of course there are all those chunks of rock and metal that are already in orbit in our solar system.

People claim to worry about global warming and seem to think that it is the major threat to our long term existence. Well, their dead wrong. The biggest threat to our existence in the long term are NEOs (Near Earth Objects). NEOs are objects made mostly of rock, like rouge asteroids, that have orbits intersecting the earths orbital plane. There are a few NEOs that are captured comets or cometary fragments.

NASA and other such agencies in the world ignored the threat for years. It wasn't until about 10 years ago that our government started some minimal funding of projects to try and log and track the numberous NEOs out there. As of yesterday there had been 783 NEOs of 1 kilometer (thats 6/10 of a mile folks) or larger identified and about 6,000 smaller objects.

But the projects are only looking for logging, and calculating the orbits of objects 100 meters or less in size. A 100 meter size asteroid of hard rock would destroy any city on earth if it impacted or exploded near it. The destruction and death would be unimaginable. For example the comet fragment or asteroid that caused the Tunguska event in Russia is estimated to have been 30 - 50 meters in size and that yeilded a blast equivlent to a 10-15 megaton hydrogen bomb (about 1,000 time more powerful than the Hiroshima bomb) causing destruction over an area of about 830 square miles!

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