  <Abridged> The impact of a meteoroid onto an asteroid transfers linear and
angular momentum to the larger body, which may affect its orbit and its
rotational state. Here we show that the meteoroid environment of our Solar
System can have an effect on small asteroids that is comparable to the
Yarkovsky and Yarkovsky-O'Keefe-Radzievskii-Paddack (YORP) effects under
certain conditions.
  The momentum content of the meteoroids themselves is expected to generate an
effect much smaller than that of the Yarkovsky effect. However, momentum
transport by ejecta may increase the net effective force by two orders of
magnitude for impacts into bare rock surfaces. This result is sensitive to the
extrapolation of laboratory microcratering experiment results to real
meteoroid-asteroid collisions and needs further study. If this extrapolation
holds, then meteoroid impacts are more important to the dynamics of small
asteroids than had previously been considered.
