That formation is on the list of interesting things for the Mars Orbiter
Camera to image during the Mars Global Surveyor mission later this year.
There are some technical issues about targeting something that small with
the high-resolution camera, though, so it might not make the cut. There's
some information about this on a web site that Mike Malin (MOC principle
investigator) maintains:
discussion of the images and techniques used:
http://www.msss.com/education/facepage/face.html
what they will try to do during MGS mapping mission:
http://www.msss.com/education/facepage/face_discussion.html
Enjoy!
Andrea