  Observations of gaseous complex organic molecules (COMs) in cold starless and
prestellar cloud cores require efficient desorption of the COMs and their
parent species from icy mantles on interstellar grains. With a simple
astrochemical model, we investigate if mechanical removal of ice fragments in
oblique collisions between grains in two size bins (0.01 and 0.1 micron) can
substantially affect COM abundances. Two grain collision velocities were
considered - 10 and 50 meters per second, corresponding to realistic grain
relative speeds arising from ambipolar diffusion and turbulence, respectively.
From the smaller grains, the collisions are assumed to remove a spherical cap
with height equal to 1/3 and 1 ice mantle thickness, respectively. We find that
the turbulence-induced desorption can elevate the gas-phase abundances of COMs
by several orders of magnitude, reproducing observed COM abundances within an
order of magnitude. Importantly, the high gaseous COM abundances are attained
for long time-scales of up to 1 Myr and for a rather low methanol ice
abundance, common for starless cores. The simple model, considering only two
grain size bins and several assumptions, demonstrates a concept that must be
tested with a more sophisticated approach.
