Super Marathon was a special combined release of M1 and M2 for the short-lived Apple Pippin game console.
The Story Page has scans of the front and back covers, and a Bungie employee provided some more details in an a.g.m post:
The game consists of a M1 and M2 with an interface for picking which game to launch. A few M2 levels are different, but I believe that they are the same differences found in M2 for the PC. Both games had changes to the terminal renderer to increase font size; even with convolution hardware, 9 point text is hard to read on a TV. Several features were ripped out to conserve memory. For example, the music in M1 is gone.
One day, someone's got to get us screenshots.