Thursday, August 16, 2012

Crests, Troughs and Waves on a Beach

  A I have mentioned that at a teleconference on Tuesday a reporter asked if one could cross the sand dunes over an apparent land bridge in one of the images shown. The problem is that there appears to be a crest to the south of Curiosity's position which prevents us from seeing all of the ground between Curiosity and Mt Sharp. There also appear to be ripples on the ground and breaks where the apparent size of the pebbles and rocks changes. To get a better idea of what is happening I drew some radial lines from Curiosity's position with the ruler tool and found that their height changed with distance when view from the side at an angle. When saved the radial lines are shown on the sidebar in Places. The Elevation Profile for a line can be viewed by right clicking on the line and selecting Show Elevation Profile in the drop down menu. The profile for the dark green line which has a heading of 150° is seen in the image below. It is roughly along the line of sight for the NASA/JPL image. The red box marks the boundary of quadrangle 51.
  If one looks at the profile one can see that there is a peak near the rover's position and this is what may be blocking our view. I marked the line of this crest with the letter C in the image above. There is also a trough along the line of sight that occurs just before where the "dunes" begin. The dunes appear to be breaking on the lower slope of Mt Sharp like waves on a beach. The reporter may also have been asking if MSL could find a path along the elevated strip at the base of Mt Sharp in order to reach the lower slopes.
  If Curiosity moved to the crest and traveled along it she would get a better view of the downward slopes and this may help to determine the best path for her to follow in the days to come.

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