I believe, as do many others, that the transparent version of the symbol means that it is currently in use, and the picture below it is just the special ability selection screen, much like it is in Diablo II. The marine itself seems to have its gun pointed straight at Nova, with his visor down. This must mean that he either saw nova before she disappeared from his sensors, or, he can just “tell that something is up”, perhaps he can see her blurry figure.

In the bottom left, we see she has 250 ammo for her C-10 canister rifle, and 50 purple balls. I’m starting to doubt that the blue meter in the top left (now at one bar) is her energy, and is rather her shields (as other people have pointed out), and that the purple things represent energy.

It should be noted that the radar in the top left has a newly colored pie piece now, yellow, as opposed to the red pie piece we saw in the screenshot of Nova and the marine before. Perhaps the yellow signifies that the marine is in a middle state of caution, where green would be relaxed, yellow would be cautious, and red is engaged.

And on a final note, there is now tactical information displayed about the marine this time. It could be that Nova needs her weapon drawn to display the information, or a certain cursor needs to be selected on the marine and a button pressed. Stay tuned for the next screenshot analysis I’ll be writing, in which we see Nova using her “see through walls” ability!