  Metal pollution in white dwarf photospheres originates from the accretion of
some combination of planets, moons, asteroids, comets, boulders, pebbles and
dust. When large bodies reside in dynamically stagnant locations -- unable
themselves to pollute nor even closely approach the white dwarf -- then smaller
reservoirs of impact debris may become a complementary or the primary source of
metal pollutants. Here, we take a first step towards exploring this possibility
by computing limits on the recoil mass that escapes the gravitational pull of
the target object following a single impact onto an atmosphere-less surface. By
considering vertical impacts only with the full-chain analytical prescription
from Kurosawa & Takada (2019), we provide lower bounds for the ejected mass for
basalt, granite, iron and water-rich target objects across the radii range
10^{0-3} km. Our use of the full-chain prescription as opposed to physical
experiments or hydrocode simulations allows us to quickly sample a wide range
of parameter space appropriate to white dwarf planetary systems. Our numerical
results could be used in future studies to constrain freshly-generated small
debris reservoirs around white dwarfs given a particular planetary system
architecture, bombardment history, and impact geometries.
