  We report the detection of widespread CH$_2$OHCHO and HOCH$_2$CH$_2$OH
emission in Galactic center giant molecular cloud Sagittarius B2 using the
Shanghai Tianma 65m Radio Telescope. Our observations show for the first time
that the spatial distribution of these two important prebiotic molecules
extends over 15 arc-minutes, corresponding to a linear size of approximately 36
pc. These two molecules are not just distributed in or near the hot cores. The
abundance of these two molecules seems to decrease from the cold outer region
to the central region associated with star-formation activity. Results present
here suggest that these two molecules are likely to form through a low
temperature process. Recent theoretical and experimental studies demonstrated
that prebiotic molecules can be efficiently formed in icy grain mantles through
several pathways. However, these complex ice features cannot be directly
observed, and most constraints on the ice compositions come from millimeter
observations of desorbed ice chemistry products. These results, combined with
laboratory studies, strongly support the existence of abundant prebiotic
molecules in ices.
