Planet Four Talk

The "martian brain" multiple optical illusion: How to see it in 4 steps.

  • Rockykrys by Rockykrys

    This “Martian Brain” picture is an incredibly deceptive multiple optical illusion: After zooming in at high resolution on screen, and rotating a few times, I would suggest that the visible features were created in this order:
    1. Generally flat “textured” red surface layer with a distinct grain running at an angle of about 30 degrees from horizontal in picture. This texture shows right across the surface and is largely not disturbed by the darker areas (which are generally still flat). The texture/grain is largely made up of fine elongated dimples and dunes – a sort of “orange peel effect”. At first I was deceived into seeing micro “u-shaped valleys”, and thought the light was coming from top left. I am now convinced the light is from bottom right of picture (also confirmed by 4. below). When viewed this way, the sides of the“elongated dimples” appear more convex, possibly indicating the way the material has settled down (rather than scoured out or striated). I am assuming that this is sand-type material which has been pushed up cracks in the underlying ice and then spilled over on its surface.
    2. Narrow cracks mostly running roughly 90 degrees across the grain, and smaller fissures (dotted lines) with the grain. Orientation of these may be coincidence. To a large extent, these do not disturb the surface grain (1) on the generally flat surface. They are certainly not broad valleys as they might first appear - see below.
    3. The "spray paint" /fan effect (dark areas) laid down over the above (1&2) on what is still a generally flat surface. This is the effect of CO2 and other debris spraying out of "geysers" and some drifting down-wind (toward top left in picture). This spray paint effect is most deceptive giving the illusion of 3D "quilting" like the surface of a brain.
    4. White 3D objects scattered on top of the above (1,2&3)? On top? This was my first thought, BUT.....on closer examination I am now thinking that these white objects are not scattered randomly. They appear to a significant extent, to follow the same grain as the surface texture (1), and some of them are slightly elongated in that direction. They are NOT convex bumps, but hollows just like the elongated dimples (1). They probably started out in the same way, then collapsed forming pits/vents at weak spots in the underlying ice. As they collapsed, they exposed their white (ice) inner edges, reflecting the light from bottom right of picture. The fact that some of them straddle the dark (“spray paint”) areas indicates that they have formed after the “geysers” had finished depositing their “spray paint” effect. Their apparent tendency to follow the grain indicates that they are not "dents" caused by a random scattering of any new objects on the surface, rather that their locations are determined by the earlier processes in the ice and surface deposits (1), perhaps influenced by rocks under the ice causing weaknesses.

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