SURPPRISES FROM THE MOON

      We often take the moon for granted, sometimes admiring its beauty, but mostly not giving it a lot of thought.  Stories of comets, and Mars and Jupiter's moons have been making the news. We thought there were no more surprises to be learned from the moon. It was a cold, lifeless unchanging world. We studied the rock samples brought back from the Apollo missions and thought we knew all the secrets of the moon. Just as suddenly, some recent data from a spacecraft orbiting the moon has turned our heads to a world much closer to home. Our moon has enough ice to fill a moderate sized lake!

 
    It all began in 1994 when the Dept. of Defense launched a spacecraft called Clementine. The purpose of the craft was to evaluate some new state of the art imaging sensors. It was decided to use the moon as a subject. Not surprisingly, this caught the interest of some planetary scientists, who decided to view the results as well as try a few things on their own.

      The imaging sensors worked better than expected. Clementine returned over 1.8 million images that have produced the best ever map of the moon. But it was not the imaging sensors that gave us the big surprise.

      Clenentine carried a communication dish and astronomers used this dish to beam radio signals into regions around the Moon's poles.  It had actually been theorized that ice could survive in the shadowed craters at the poles, but until now no-one had the chance to really look.

      The idea was to bounce radio signals off the cratered areas and then use radio dishes here on earth to look for reflections. This is analogous to looking for light bouncing off a roadside reflector when your headlights hit it.

  
   To the delight of the planetary scientists, there were telltale signs of water ice mixed in with the lunar soil. Apparently the ice extends down to about 50 feet in an area of 40 square miles!
 
      The mystery comes into play when the question is asked about how the ice got there in the first place. Analysis of all the rock samples brought back by the Apollo missions tell us that the moon is a dry place. So it is not possible that the water came from within the moon. So from where did it come?

      The best explanation for the water ice on the moon may be with comets. Comets have longed been dubbed "dirty snowballs." This is because they are composed largely of water ices and other compounds, including organic compounds.  If a comet impacted onto the surface of the moon, it is highly possible that some of the ice could have been trapped in the dark recesses of a crater.

      It is probable the over the last 3 billion years, thousands of comets have hit the moon. An impact or two could  easily be responsible for the ice on the moon.

      An impact by a comet releases a water vapor cloud. If the water vapor settles into a cold trap (such as a permanently shadowed crater) the water ice remains trapped. Since over 3 billion years have passed, we may have accumulated a substantial amount of water ice.

       This discovery is important for future manned missions in space. Not only will this stash of water ice give a record of cometaryu impacts over time, it misht also support a human colony on the moon. Such a colony would also produce fuel for future solar system expeditions. This future colony would separate water ice into liquid hydrogen and liquid oxygen for rocket fuel, in fact, it is the same fuel that powers the space shuttle.

      Science Fiction stories from the 50's , 60,s and later often mentioned humans having moonbases where people lived and worked. This recent discovery has taken us a step closer to the dreams of those who wrote such stories.