Keeping the sky from falling

Most people seem to have little interest in space.  They perhaps believe that nothing that goes on off-planet will affect them.  Yet, it has been shown that rocks falling on Earth can affect us.  Most recently, a city in Russia, Chelyabinsk Oblast, was nearly hit by a meteor large enough to destroy a building, and the shock waves damaged hundreds of buildings.  There are geological remains of impact craters kilometers across, and photographs of the results of a meteor blast which leveled trees for kilometers around.

Detecting these rocks from here on Earth can be very difficult, because they are dark and do not reflect very much light.  Also, some of them spend most of their time between the Earth and the Sun, so they are nearly impossible to see.  Back in the early 1990’s, a rock over a kilometer across passed between the Earth and  the Moon, and no one knew it was there until it was between the Earth and the Moon.  A rock that size would destroy an entire region, and could potentially cause extreme weather which would make life on Earth very difficult.  An impact of a similar size 65 million years ago is almost certainly what ended the long reign of the dinosaurs.

From outer space, rocks are much easier to detect, because they reflect some of the thermal energy of the Sun.  A satellite close to the orbit of Venus would be able to detect any large rocks with orbits near the Earth’s, and could also detect any intruders from the outer Solar System.  A few hundred million dollars for such a satellite does not seem too expensive to insure that we do not get blind-sided by a big rock.

 

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