Whilst perusing the MSSS picture M14-00689 I found the following.

A close look at this portion of the picture made me do a double take.

Found just below the dark crater, other than being cropped out and a slight gamma correction it's unmodified.

Here's a larger Gamma correction.

This looks like an "h" and an "E" or maybe a "B". Now h-E, if that's what it is, could mean anything thing but "hElp" is what sprung to my mind. Unfortunately, there is no other picture next to this strip and gamma correcting the crater doesn't reveal anything before the "h". Just another martian oddity.