Bright Explosion on the Moon   
       
   May 17, 2013:  For the past 8 years, NASA astronomers have been monitoring the   
   Moon for signs of explosions caused by meteoroids hitting the lunar surface.   
   "Lunar meteor showers" have turned out to be more common than anyone expected,   
   with hundreds of detectable impacts occurring every year.   
       
   They've just seen the biggest explosion in the history of the program.   
       
   "On March 17, 2013, an object about the size of a small boulder hit the lunar   
   surface in Mare Imbrium," says Bill Cooke of NASA's Meteoroid Environment   
   Office. "It exploded in a flash nearly 10 times as bright as anything we've   
   ever seen before."   
       
   http://www.youtube.com/watch?v=IYloGuUZCFM   
       
   A new ScienceCast video describes the bright lunar explosion of March 17,   
   2013. Play it   
       
   Anyone looking at the Moon at the moment of impact could have seen the   
   explosion--no telescope required.  For about one second, the impact site was   
   glowing like a 4th magnitude star.   
       
   Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to   
   notice the impact in a digital video recorded by one of the monitoring   
   program's 14-inch telescopes.  "It jumped right out at me, it was so bright,"   
   he recalls.   
       
   The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling   
   56,000 mph.  The resulting explosion1 packed as much punch as 5 tons of TNT.   
       
   http://science.nasa.gov/media/medialibrary/2013/05/16/frames.jpg   
       
   These false-color frames extracted from the original black and white video   
   show the explosion in progress. At its peak, the flash was as bright as a 4th   
   magnitude star. [still frames] [video]   
   Cooke believes the lunar impact might have been part of a much larger event.   
       
   "On the night of March 17, NASA and University of Western Ontario all-sky   
   cameras picked up an unusual number of deep-penetrating meteors right here on   
   Earth," he says. "These fireballs were traveling along nearly identical orbits   
   between Earth and the asteroid belt."   
       
   This means Earth and the Moon were pelted by meteoroids at about the same time.   
       
   "My working hypothesis is that the two events are related, and that this   
   constitutes a short duration cluster of material encountered by the Earth-Moon   
   system," says Cooke.   
       
   One of the goals of the lunar monitoring program is to identify new streams of   
   space debris that pose a potential threat to the Earth-Moon system.  The March   
   17th event seems to be a good candidate.   
       
   Controllers of NASA's Lunar Reconnaissance Orbiter have been notified of the   
   strike.  The crater could be as wide as 20 meters, which would make it an easy   
   target for LRO the next time the spacecraft passes over the impact site.    
   Comparing the size of the crater to the brightness of the flash would give   
   researchers a valuable "ground truth" measurement to validate lunar impact   
   models.   
       
   http://science.nasa.gov/media/medialibrary/2013/05/16/impacts.jpg   
       
   NASA's lunar monitoring program has detected hundreds of meteoroid impacts.   
   The brightest, detected on March 17, 2013, in Mare Imbrium, is marked by the   
   red square. Unlike Earth, which has an atmosphere to protect it, the Moon is   
   airless and exposed.  "Lunar meteors" crash into the ground with fair   
   frequency. Since the monitoring program began in 2005, NASA's lunar impact   
   team has detected more than 300 strikes, most orders of magnitude fainter than   
   the March 17th event.  Statistically speaking, more than half of all lunar   
   meteors come from known meteoroid streams such as the Perseids and Leonids.    
   The rest are sporadic meteors--random bits of comet and asteroid debris of   
   unknown parentage.   
       
   U.S. Space Exploration Policy eventually calls for extended astronaut stays on   
   the lunar surface.  Identifying the sources of lunar meteors and measuring   
   their impact rates gives future lunar explorers an idea of what to expect. Is   
   it safe to go on a moonwalk, or not?  The middle of March might be a good time   
   to stay inside.   
       
   "We'll be keeping an eye out for signs of a repeat performance next year when   
   the Earth-Moon system passes through the same region of space," says Cooke.   
   "Meanwhile, our analysis of the March 17th event continues."   
       
   For updates stay tuned to science.nasa.gov.   
       
   Footnote: (1)  The Moon has no oxygen atmosphere, so how can something   
   explode? Lunar meteors don't require oxygen or combustion to make themselves   
   visible.  They hit the ground with so much kinetic energy that even a pebble   
   can make a crater several feet wide.  The flash of light comes not from   
   combustion but rather from the thermal glow of molten rock and hot vapors at   
   the impact site.   
       
   Credits:   
       
   Author: Dr. Tony Phillips | Production editor: Dr. Tony Phillips | Credit:   
   Science@NASA   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.92   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)