The images from the rovers are available in many different formats customized for different audiences. Although the cameras are stereo (i.e., they can acquire a left and right-eye image), not all images are taken in this mode. Many are taken with only one eye. This is done when the 3D depth information is not necessary or when there are limits on bandwidth or on-board storage. When stereo images are received, they are received as separate images and it takes significant book keeping to find images that have a matched stereo pair. If you are a member of the visualization alliance and are using JPL's File Exchange Interface (FEI) client to mirror the data from JPL, you might find the following Stereo Searching Perl Script helpful. Note, you will have to customize some variables at the top of the script to your site.