  We have imaged the emission from the near-infrared v=1-0 S(1), 1-0 S(7), 2-1
S(1) and 6-4 O(3) lines of molecular hydrogen in the N- and SW-Bars of M17,
together with the hydrogen Br-gamma and Br-10 lines. This includes the first
emission line image ever to be obtained of a line from the highly excited v=6
level of H2. In both Bars, the H2 emission is generally distributed in clumps
along filamentary features. The 1-0 S(1) and 2-1 S(1) images have similar
morphologies. Together with their relative line ratios, this supports a
fluorescent origin for their emission, within a photodissociation region. The
SW-Bar contains a clumpy medium, but in the N-Bar the density is roughly
constant. The 1-0 S(7) line image is also similar to the 1-0 S(1) image, but
the 6-4 O(3) image is significantly different to it. Since the emission
wavelengths of these two lines are similar (1.748 to 1.733um), this cannot be
due to differential extinction between the v=6 and the v=1 lines. We attribute
the difference to the pumping of newly formed H2 into the v=6, or to a nearby,
level. However, this also requires either a time-dependent photodissociation
region (where molecule formation does not balance dissociation), rather than it
to be in steady-state, and/or for the formation spectrum to vary with position
in the source. If this interpretation of formation pumping of molecular
hydrogen is correct, it is the first clear signature from this process to be
seen.
