Imaging Experiments

Reproducing The Effective Field Of The Microscopic Imager

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   One of the goals of this series of experiments is to reproduce the effective field and resolution of the MER microscopic imagers.  I used a common digital camera as the imaging device.  I have the Agfa ePhoto 1280 digital camera, which has a field of 1024 x 960 pixels.  This yields roughly 94% of the image field of the microscopic imagers, which is close enough that we can use a simple magnifier and get images that are virtually identical to the NASA images.

   I started by gathering red earth and filtering the sand so that only the finer particles would be used.  I wanted to reproduce the texture and color of the original soil as closely as practical for the experiment.

   I selected a mound of soil that also showed similar caking properties to the images from both Spirit and Opportunity.  I gathered about 2 kilograms of this dried soil for the experiments.

   Once gathered, I found that there was a considerable amount of organic material that had to be removed.  The simplest expedient was to construct a filter from materials at hand.  This was fast and cheap, and also meant that anyone else could easily perform the same sort of operation with minimal cost and labor.
   I used a large jar and fine mesh nylon fabric as a filter.  I broke up the dried clods and poured the soil directly into the jar.  I stretched a length of the doubled thickness nylon mesh (from a discarded pair of stockings) over the mouth of the jar.

   To secure the makeshift filter, I used a stout rubber band.  A large plastic funnel was then placed over the filter to direct the filtered particles into a plastic "shoe box" container.

   As the jar was shaken upside-down into the funnel, a stream of clean, fine sand particles emerged and filled the bottom of the plastic container.

   One of the first observations was that the granular size of the particles was particularly fine, and that it might not be large enough to accurately reproduce the texture of the Martian soil.
   The use of a magnifier with the camera soon showed that the granule size was approximately what I wanted for the recreation.

   A selection of small limestone pieces was placed in the sand in three different ways in an effort to duplicate the placement seen in the images from Mars.

   This shows the limestone fragments after being turned into the sand and mixed thoroughly.  The container was then shaken a bit to help them migrate to the surface.  The pieces ended up half buried in most instances, with some completely hidden and others almost completely exposed.

   Overall, the effect was only partly satisfactory.  The texture of the soil did not emulate the actual appearance as well as I had hoped.  It was too flaccid, reaching the angle of repose and slumping into low mounds that would collapse at the slightest movement or jogging.  There was no cohesion as the Martian soil exhibits.   

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