  Dynamically new comet C/2011 L4 (PanSTARRS) is one of the brightest comets
since the great comet C/1995 O1 (Hale-Bopp). Here, we present our
multi-wavelength observations of C/2011 L4 during its in-bound passage to the
inner Solar system. A strong absorption band of water ice at 2.0 $\mu$m was
detected in the near infrared spectra, taken with the 8-m Gemini-North and 3-m
IRTF telescopes. The companion 1.5 $\mu$m band of water ice, however, was not
observed. Spectral modeling show that the absence of the 1.5 $\mu$m feature can
be explained by the presence of sub-micron-sized fine ice grains. No gas lines
(i.e. CN, HCN or CO) were observed pre-perihelion either in the optical or in
the sub-millimeter. 3-$\sigma$ upper limits to the CN and CO production rates
were derived. The comet exhibited a very strong continuum in the optical and
its slope seemed to become redder as the comet approached the Sun. Our
observations suggest that C/2011 L4 is an unusually dust-rich comet with a
dust-to-gas mass ratio $>$ 4.
