| I think it was just an amazing coincidence. NASA has some info about it here: http://www.jpl.nasa.gov/news/news.php?release=2013-061 It certainly would not look good for NASA if this had hit the US, but unfortunately objects this small are just too hard to find I guess. If an object this small did a tremendous amount of damage and occurred frequently, then it would be worth more investment to try and find the smaller objects. If something like this does only occur every 100 years, or even more frequent than that, it's still not worth it I guess. Eventually there does need to be a plan on what to do if something large ever threatened. The odds are astronomically low, so I guess for now we can wait until technology gets better to detect the smaller ones and eventually deflect the larger ones in some way if one ever threatened. I guess it may be surprising to some people that an object like this was not spotted prior to hitting, but it really was quite small. It could have been several times larger and still not have been spotted. NASA does not even track these. "Potentially Hazardous Asteroids (PHAs) are currently defined based on parameters that measure the asteroid's potential to make threatening close approaches to the Earth. Specifically, all asteroids with an Earth Minimum Orbit Intersection Distance (MOID) of 0.05 AU or less and an absolute magnitude (H) of 22.0 or less are considered PHAs. In other words, asteroids that can't get any closer to the Earth (i.e. MOID) than 0.05 AU (roughly 7,480,000 km or 4,650,000 mi) or are smaller than about 150 m (500 ft) in diameter (i.e. H = 22.0 with assumed albedo of 13%) are not considered PHAs. There are currently 1381 known PHAs. This "potential'' to make close Earth approaches does not mean a PHA will impact the Earth. It only means there is a possibility for such a threat. By monitoring these PHAs and updating their orbits as new observations become available, we can better predict the close-approach statistics and thus their Earth-impact threat." From: http://neo.jpl.nasa.gov/neo/groups.html More: http://spaceweather.com/ |