  Short-duration Gamma-ray bursts (GRBs) (\leq 2{\rm s}) have remained a
mystery due to the lack of afterglow detection until recently. The models to
interpret short GRBs invoke distinct progenitor scenarios. Here we present a
generic analysis of short GRB afterglows, and calculate the optical lightcurves
of short GRBs within the framework of different progenitor models. We show that
all these optical afterglows are bright enough to be detected by the
Ultraviolet and Optical Telescope (UVOT) on board the {\em Swift} observatory,
and that different models could be distinguished with a well-monitored
lightcurve. We also model the afterglow data of the recently discovered short
burst GRB 040924. We find that the limited data are consistent with a low
medium density environment which is consistent with the pre-concept of the
compact-star merger progenitor model, although the models with a collapsar
progenitor are not ruled out.
