We present observations and an interpretative model of the dust environment of Main-Belt Comet P/2010 F5 ( Gibbs ) .
The narrow dust trails observed can be interpreted unequivocally as an impulsive event that took place around 2011 July 1st with an uncertainty of \pm 10 days , and a duration of less than a day , possibly of the order of a few hours .
The best Monte Carlo dust model fits to the observed trail brightness imply ejection velocities in the range 8-10 cm s ^ { -1 } for particle sizes between 30 cm and 130 \mu m. This weak dependence of velocity on size contrasts with that expected from ice sublimation , and agrees with that found recently for ( 596 ) Scheila , a likely impacted asteroid .
The particles seen in the trail are found to follow a power-law size distribution of index \approx –3.7 .
Assuming that the slowest particles were ejected at the escape velocity of the nucleus , its size is constrained to about 200-300 m in diameter .
The total ejected dust mass is \gtrsim 5 \times 10 ^ { 8 } kg , with represents approximately 4 to 20 % of the nucleus mass .