  Based on three years of deep observations of the Galactic center with the
Chandra X-ray Observatory, we report the discovery of changes in the
intensities and morphologies of two hard X-ray nebulosities. The nebulosities
are dominated by fluorescent iron emission, and are coincident with molecular
clouds. The morphological changes are manifest on parsec scales, which requires
that these iron features are scattered X-rays from a 2 or 3-year-long outburst
of a point source (either Sgr A* or an X-ray binary) with a luminosity of at
least 1e37 erg/s. The variability precludes the hypotheses that these nebulae
either are produced by keV electrons bombarding molecular clouds, or are
iron-rich ejecta from supernovae. Moreover, the morphologies of the reflection
nebulae implies that the dense regions of the clouds are filamentary, with
widths of ~0.3 pc and lengths of ~2 pc.
