The smeared "gunk" is visible -- in great detail -- at the lower right and lower left corners of the photo (nearest the lander, of course).
That stuff looks really wierd! It's hard to imagine how dragging an airbag across a (supposedly) dry, sandy surface (with a litle gravel tossed in) could form such a gummy-looking surface mark...
This goes to prove that, "As man extends the radius of his knowledge, he expands the circumference where he contacts his igoarance by a factor of 2Pi."
If the airbags were constructed of rubber and nylon or similar synthetic materials, then dragging them across the surface might create static electricity just as our walking over a synthetic carpet does. We'll have to admit, the environment is perfect for the creation of static electricity: extremely cold and dry. Until further investigation reveals otherwise, the static electricity hypothesis is most appealing to me.
