  We report the discovery in NIR with SofI at the NTT of a resolved
circumstellar dust disk around a 2MASS source at the periphery of the rho
Ophiuchi dark cloud. We present follow-up observations in J, H, and Ks-band
obtained with ISAAC at the VLT, under 0.4"-seeing conditions, which unveil a
dark dust lane oriented East-West between two characteristic northern and
southern reflection nebulae. This new circumstellar dust disk has a radius of
2.15" (300 AU at 140 pc), and a width of 1.2" (170 AU at 140 pc). Thanks to its
location at the periphery of the dense cores, it suffers small foreground
visual extinction (Av=2.1\pm2.6 mag). Although this disk is seen close to
edge-on, the two reflection nebulae display very different colors. We introduce
a new NIR data visualization called ``Pixel NIR Color Mapping'', which allows
to visualize directly the NIR colors of the nebula pixels. Thanks to this
method we identify a ridge, 0.3" (40 AU at 140 pc) to the north of the dark
lane and parallel to it, which displays a NIR color excess. This ridge
corresponds to an unusual increase of brightness from J to Ks, which is also
visible in the NTT observation obtained 130 days before the VLT one. We also
find that the northern nebula shows ~3 mag more extinction than the southern
nebula. We compute axisymmetric disk models to reproduce the VLT scattered
light images and the spectral energy distribution from optical to NIR. Our best
model, with a disk inclination i=86\pm1 deg, correctly reproduces the extension
of the southern reflection nebula, but it is not able to reproduce either the
observed NIR color excess in the northern nebula or the extinction difference
between the two reflection nebulae. We discuss the possible origin of the
peculiar asymmetrical NIR color properties of this object.
