  We present initial observations of the newly-discovered active asteroid
313P/Gibbs (formerly P/2014 S4), taken to characterize its nucleus and
comet-like activity. The central object has a radius $\sim$0.5 km (geometric
albedo 0.05 assumed). We find no evidence for secondary nuclei and set (with
qualifications) an upper limit to the radii of such objects near 25 m, assuming
the same albedo. Both aperture photometry and a morphological analysis of the
ejected dust show that mass-loss is continuous at rates $\sim$0.2 to 0.4 kg
s$^{-1}$, inconsistent with an impact origin. Large dust particles, with radii
$\sim$50 to 100 $\mu$m, dominate the optical appearance. At 2.4 AU from the
Sun, the surface equilibrium temperatures are too low for thermal or
desiccation stresses to be responsible for the ejection of dust. No gas is
spectroscopically detected (limiting the gas mass loss rate to $<$1.8 kg
s$^{-1}$). However, the protracted emission of dust seen in our data and the
detection of another episode of dust release near perihelion, in archival
observations from 2003, are highly suggestive of an origin by the sublimation
of ice. Coincidentally, the orbit of 313P/Gibbs is similar to those of several
active asteroids independently suspected to be ice sublimators, including
P/2012 T1, 238P/Read and 133P/Elst-Pizarro, suggesting that ice is abundant in
the outer asteroid belt.
