Sounds like a neat idea. You could project the panorama at the virtual horizon level, and fill in the sky with projected color that matches the sky in the images.

My memory of planetariums, though, is that they're cluttered at horizon level, with people and machinery, and that the seats are intended for gazing up for extended periods. An existing facility might be a little awkward.

You could design a "planetarium" (mutating the meaning of the word a bit) specially for this purpose, and the equipment requirements would be a lot simpler. Project the image on the inside of a dome, and if you plan the sight lines carefully, people will be able to walk around and study images up close. Possibly you'd create a simulated Mars surface for extra versimilitude.

Projection could be from the outside onto a translucent dome, but I expect that that would be expensive in terms of the special material and fairly large number of projectors required around the circumference. An alternative that comes to mind is based on a new type of camera that real estate people use to take 360 degree interior views. It has an extreme fisheye lens that you point straight up, and it capture a complete hemisphere projected on to flat film. You need software to reproject it into a pannable image suitable for human viewing. Seems to me that a similar process could be used to project a Mars panorama inside a dome, from up at the zenith, using an image that's been prewarped to project on a hemisphere. Then you'd have just one projector, and people could still get within a few feet of the dome walls before they block the projection.

Didn't JPL post panoramic images in a circular (ring-shaped) projection, in the early days of MER? I think they were intended to be printed very large, a hole cut in the center, and you'd stick your head up inside to take a look around. In any case, circular projections of panoramae are nothing new.