  On 2019 January 5 a streamer associated with the 4--10 km main-belt asteroid
(6478)~Gault was detected by the ATLAS sky survey, a rare discovery of activity
around a main-belt asteroid. Archival data from ATLAS and Pan-STARRS1 show the
trail in early December 2018, but not between 2010 and January 2018. The
feature has significantly changed over one month, perfectly matching
predictions of pure dust dynamical evolution and changes in observing geometry
for a short release of dust around 2018 October 28. Follow-up observations with
HST show a second narrow trail corresponding to a brief release of dust on 2018
December 30. Both releases occurred with negligible velocity. We find the dust
grains to be fairly large, with power-law size distributions in the $10^{-5} -
10^{-3}$~m range and power-law indices of $\sim -1.5$. Three runs of
ground-based data find a signature of $\sim 2\,\rm h$ rotation, close to the
rotational limit, suggesting that the activity is the result of landslides or
reconfigurations after YORP spin-up.
