  We investigate the anisotropy in cosmic microwave background Planck maps due
to the coupling between its beam asymmetry and uneven scanning strategy.
Introducing a pixel space estimator based on the temperature gradients, we find
a highly significant (~20 \sigma) preference for these to point along ecliptic
latitudes. We examine the scale dependence, morphology and foreground
sensitivity of this anisotropy, as well as the capability of detailed Planck
simulations to reproduce the effect, which is crucial for its removal, as we
demonstrate in a search for the weak lensing signature of cosmic defects.
