1: If you're trying to see detail in an image, get a higher-resolution version; low-res jpegs are not something that you can extract any amount of detail from.
2: If you're trying to see detail in a low-res jpeg, fuggetaboutit. You can't magically increase the amount of detail in
any image by blowing it up. Jpegs use pixels (they're raster graphics), they are not vector graphics.
3: Your yellow lines are along some very randomly placed ridges in the rock. If you look closely at your image from Keith Laney's site and of your own, you'll notice that this rock isn't symmetrical. Where the "forehead" would be (that smooth highlighted part above the rest of the "face") is all screwed up. The far ridge that looks like an eyebrow is at a very different angle than the other one, and it's also taller. The area beyond the far eyebrow ridge also seems to meld with it instead of what you would think it would do (look like a seperate piece)
You'll notice that the area in the following image that's in a box is not in shadow. In fact, the rest of the rock isn't in shadow either.
If you look at
any of the rocks in the original image, found
here, you'll notice that the light is coming from a very distinct direction: approximately the upper-left corner. Furthermore, the rock in question is angled towards the camera. This seems to imply that the "eyebrow" ridge that is closest to the ground is a ridge that is being lit by the sun followed by more ridges going towards the right of the image.
If you look at
this image you'll notice that the rock has a point on its upper-left corner, if I'm not wrong about the lighting. If I'm right about the lighting (which wouldn't be hard to get right, considering the abundance of shadows), then it has a sort of point that is protruding towards the camera. Why is this significant? If that point is casting a shadow in the rest of the rock like that, then shouldn't it stand to reason that any other rock with a protuberance sticking towards the camera should cast a shadow on itself in the same way? What I'm trying to say is that, based on the rest of the image, that "face", or whatever it's supposed to be, is angled towards the camera and it's casting shadows on itself, thereby making seem like it's slightly symmetric (which it's not*).
*See third paragraph.