May 21, 2008 | David F. Coppedge

Moon Still Feeling the Impact

Craters on the moon seem so old.  Astronomers count them to try to figure out how long ago the surface was battered by impacts.  Although amateurs have claimed to see flashes on the moon’s surface through backyard telescopes, serious astronomers dismissed many of the reports as stories from the lunatic fringe.  “Not any more,” says Space.com and PhysOrg.  NASA astronomers decided to watch a little more closely and have so far counted over 100 flashes in the last two and a half years.
    More impacts occur during known meteor showers, but there is never a time of year that is impact-free.  “A typical blast is about as powerful as a few hundred pounds of TNT and can be photographed easily using a backyard telescope,” said an observer at Marshall Space Flight Center.
    A good question is why this was never noticed before.  The moon is, after all, our closest neighbor in space.  Astronomers at Marshall decided to start looking in late 2005 when NASA announced plan to return astronauts to the moon.  They figured we had better understand better the risk of impacts.  Though the chance of an astronaut being hit directly is nil, the article explained that debris can shoot out sideways like bullets for long distances.  These “secondary impacts” are of greater concern for extended visits or lunar bases.  A spacesuit could be pierced by a particle as small as a millimeter.
    The reporter said that while the article was being written, three more flashes on the moon were recorded.  The PhysOrg article included a map of the impacts seen since 2005, and a video of a bright explosion.

The article did not delve into a follow-up question: if impacts are coming in this frequently, how many would have occurred at this rate over the assumed age of the solar system?  And what effect would the explosions have had on the lunar surface?  Let’t do a little back-of-the-envelope calculation.  A hundred impacts over 2.5 years is 40 per year.  Over 4 billion years, that would equate to 160 billion impacts.
    Keep in mind, though, that 100 is all that was observed.  We can only see the near side of the moon, so assume another 100 or more hits the parts we cannot see.  Also, the moon is not observable all month due to lunar phases and weather.  It is very likely the impact rate is considerably higher.  And by most astronomical reckonings, the impact rate was much higher in the past, when the moon was formed and during the “late heavy bombardment” postulated by leading solar system models.
    Yet we see large areas of the moon with few impacts.  Some of the maria are nearly as smooth as when the lava flowed supposedly billions of years ago.  Wouldn’t it seem plausible that this continuous rain of impactors would have churned up the surface and coated the moon with a substantial layer of dust from secondary debris?
    You might recall that the Apollo astronauts could scratch bedrock with the toes of their boots in many places.  Without the necessary fiction of billions of years for Darwin, this would be easily explained as evidence the moon is relatively young.
    The earth gets bombarded continually, too.  Fortunately for living things, our atmosphere burns up most fragments harmlessly high above us, providing us not only safety, but a nightly fireworks show in celebration of our privileged planet.

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Categories: Solar System

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