See also those images.

The first three images are for viewing with crossed eyes.
All the three pictures are the same, just scaled down - chose
the best resulution you are comfortable with.

The next three images are for viewing with relaxed to infinity eyes.
All the three pictures are the same, just scaled down - chose
the best resulution you are comfortable with.

All those messages are by NASA, they were posted on a free
available website (http://marsrovers.jpl.nasa.gov/gallery/all/spirit.html),
so I assume giving NASA full credit I can copy the images here.
I'm not a lawyer, but I hope this disclaimer is enough.