Monday, June 29, 2015

      Are We Safe From Meteors?

     Does this look like a place hit by a meteor?  The quaint town of Noerdlingen, Germany, lying between Munich and Stuttgart, certainly looks peaceful in  this view from its ancient church tower, known to locals as the Daniel.  But about fourteen and a half million years ago, a meteorite more than a kilometer in diameter slammed into the earth,creating a crater over twenty-eight kilometers across. The force was so great, equivalent to nearly two million Hiroshima-style bombs, that tons of diamonds were instantly compressed into existence.  The native stone in the town's buildings is peppered with tiny, glistening jewels.  Rocks were thrown hundreds of of kilometers away, into what is now the Czech Republic. Despite endless years of erosion, the giant crater is easily visible from space and the rim can be traced through the surrounding woods and fields.   A smaller crater in nearby Steinheim, thought to be formed by a fragment of the same meteor, is more easily appreciated from the ground, since it is under two kilometers wide.
     The recent flyby by a meteor much, much smaller, raised some alarms on Earth, although scientists had calculated that it would miss our planet by a fortunately large margin.  Still, it is almost inconceivable how much damage to our present civilization an impact on the scale of the one that formed the Noerdlingen-Ries crater would produce.  To avert such a catastrophe, measures are being taken.  Earlier this month, NASA announced a new initiative to investigate possible ways of dealing with approaching meteors with nuclear weapons, as portrayed in the sci fi movie Armageddon.  The agency also recently released a  map showing impacts with small meteorites called fireballs or bolides over the last couple of decades.   Furthermore, a study by Stefan Hergarten and Thomas Kenkmann of the University of Freiburg reveals that almost all of the large impact craters on Earth have already been discovered and that the theories about the rareness of such collisions are probably correct.  
     The news from Freiburg offers some comfort for those worried, like Chicken Little, that the sky is in imminent danger of falling.  Further comfort may come from the fact that our space programs are now mainly focused on asteroids, comets, and meteors.  The impetus for this interest is not, it is true, simply a matter of prudence.  Greed plays a large part, since the prospects of asteroid mining are driving the imaginations of NASA authorities and private enterprise alike.  One asteroid has been identified that might contain many times the total amount of gold ever found on Earth.  This would be nice to have in one's bank account, but before we start hallucinating about the benefits, we should remember that the discovery of vast new sources of gold in Mexico and Peru by the conquistadores wound up destroying the economy of Spain just at the moment it was about to dominate most of Europe.  At the same time, we need not be so pessimistic that we ignore the opportunity to control our planetary destiny better than we do now.  Nuclear bombs have a privileged place in Washington's psyche, but hopefully scientists can also point out possibilities of rerouting meteors with new technology such as ion drives.  
      We can never count ourselves as totally safe from meteors.  Our understanding of events out at the edge of the solar system, in the mysterious Kuiper Belt and the Oort Cloud, is still too incomplete to rule out the appearance of some "unscheduled" visitor from space bashing into our world. However, if we follow the advice of the reporter at the end of The Thing From Another World and "keep watching the skies," we may preserve Noerdlingen behind its quaint medieval town wall (one of only three remaining in Deutschland) and the rest of us in our cities, suburbs and farms.