One can always check the drive log here to see how much change in position the rover had between two images: curiositylog.com...
Between this image and
this image, Curiosity moved 16.17 meters.
And that's why the rocks disappeared.
I made a cross-eyed stereo image from two of the images in the OP:
("NRB" for "right eye")
(NLB for "left eye")
Both taken on Sol 550.
That can be done because the images were taken by a stereo camera - one lens for the right eye and another for the left, to simulate human binocular
vision. We see in 3D because each eye presents a slightly different view, giving us a depth perception. I will post here a cropped out section of the
stereo image that contains the rocks in question:
In order to view it in 3D, one has to slightly cross his eyes, viewing the computer screen from arm's length away, until the two images merge into one
central image. It takes a bit of practice, and one out of ten cannot do it at all, but what you get in the end is a 3 dimensional view. We can see in
the 3D view that the disappearing rocks are slightly below a rise in the landscape, on the far side of it. If the camera drops just a couple of inches
(i.e. sits a couple inches lower on the terrain during the move) the rocks disappear altogether behind the slight rise. What actually happened was
Curiosity was climbing the rise during the time interval from Sol 549 to Sol 550, and the two rock hove into view as the camera elevation increased
and it could see over the crater rim. They didn't "disappear", they appeared.
In this image, "NLB" is actually on the right, and "NRB" is on the left, because the eyes must cross to get the 3D effect, making the left eye look to
the right image (the left eye image) and the right eye look to the left image (the right eye image).
Beyond the rocks appears to be a bowl shaped depression, probably a crater. The rocks that disappear are sitting just inside the rim of it. The big
rock, used for reference, is sitting atop a slight pedestal of dirt, which is why it didn't disappear as well.
I used Stereo Photo Maker
, a freeware program, to make the stereo image. If anyone wants it in a
red-cyan anaglyph version, or simply side by side, I can do that as well if it helps you to see the terrain. Just drop me a U2U and I'll post them in
the thread if anyone wants them.
ETA: The picture got shrunk to fit into the thread. If you right click on it and download the image to your desktop, then view it, it will be bigger
edit on 2014/2/25 by nenothtu because: (no reason given)