The picture symbolizing the most the 50 years of space exploration (in magazines)
Bruce McCandless during his 1984 EVA, free from the shuttle, alone in the vastness of space!!
It shows a few things: a new freedom acquired (but it can only last a few hours); man truly in space (the spacesuit being the necessary outfit for the spaceman-there's no spaceman without a spacesuit);
However: the MMU hampered the astronaut's ability to work with his hands (the robotarm being much more useful) and the MMU didn't last further than that year!
It's irony (or is it a warning sign?) that what symbolized the ultimate freedom turned out not to be a useful tool after all.