Mars InSight landing spot photos suggest not so deep permafrost

~Atmospheric refraction of a CO2 atmosphere is probably visible,  more dedicated photos are required though.
~First photographic hints at very slight horizon refraction
~Given the thinness of the atmosphere, much of this of course was expected,  but further very serious photography should be undertaken.

    Mars has a 6 mb atmosphere,  169 times less weighty than on Earth.  Not many refraction specialists believe it capable of causing some atmospheric mirages,  but near the horizon,  the game changes, at that level,  we look at a much thicker atmosphere.  Consider what we always knew,  Mars landscape looked carved by water ever since a closer telescopic look at the planet was achieved.   Now that we have access to a probe capable of staying still,  by refraction optics we can see if there is any ice permafrost,  which can give a spectacular effect similar to sea ice horizons on Earth.

     Ice and Martian soil should have different specific heat capacity,  ice has most certainly  a greater heat capacity, which means that it affects the soil right over it,  in particular,   when the cloudless sunny sky  hits a pure rocky outcrop,  the air right above warms up rapidly,  this may cause a "road mirage"  like on Earth,  however subtle likely so on Mars, but none heard of so far.   Examples here show no rapid lowering,  a sure sign of a permeating factor.  Here we study the Martian horizon,  by NASA design from a probe not moving around all over the place:

NASA InSight December 5 and 7 2018 .  15:27  and at 11:34 local mean solar time respectively,  the 5th has greater shadow to the right.  The robotic arm has likely moved around, and is placed back not always exactly  in this same resting spot.   The pictures are aligned,  with your mouse pointer, verify carefully the positions of nearest rocks,  now look at the horizon.  Point your mouse at any point on the horizon line,  you will see the darker image having a very slightly higher horizon throughout.  The darker image is nearest local noon, with warmest sun effects,  was likely taken with an optical filter.  If there is near surface permafrost the horizon should eventually lower,  in this case the horizon lowered perhaps further and is now rising towards the near noon height, meaning the ground horizon has sea ice properties,  namely frozen water....

  Experience on Earth dictates:  top of sea ice warms enough to lower the horizon after local apparent noon, given no great weather change,   this usually happens a few hours after noon.  The brighter image here is at 3:27 PM usually at about the same time when the sea ice horizon reaches lower point on Polar Earth.

     CO2 Martian atmosphere may cause different refraction effects,  namely 95% CO2 concentration surely gives a great  warming potential,  so the surface should warm really rapidly when the sun rises, again a dry rocky substratum horizon should lower at local apparent noon,  not take a few hours as on Earth.  Which as we know,   on any given sunny day without much great weather circulation,  noon is not the warmest time of day.

   A rudimentary model using refraction index of CO2 gas,  incidentally greater than air at standard pressures and temperatures,  calculates a very small shrinking of the vertical sun disk equally at  the horizon.  However,  the interplay between Martian soil, permafrost and CO2 atmosphere is novel,  more studying is needed.  WD December 9 2018