  White dwarfs that have accreted rocky planetary bodies provide unique
insights regarding the bulk composition of exoplanetary material. The analysis
presented here uses observed white dwarf atmospheric abundances to constrain
both where in the planetary system the pollutant bodies originated, and the
geological and collisional history of the pollutant bodies. At least one, but
possibly up to nine, of the 17 systems analysed have accreted a body dominated
by either core-like or mantle-like material. The approximately even spread in
the core mass fraction of the pollutants and the lack of crust-rich pollutants
in the 17 systems studied here suggest that the pollutants are often the
fragments produced by the collision of larger differentiated bodies. The
compositions of many pollutants exhibit trends related to elemental volatility,
which we link to the temperatures and, thus, the locations at which these
bodies formed. Our analysis found that the abundances observed in 11 of the 17
systems considered are consistent with the compositions of nearby stars in
combination with a trend related to elemental volatility. The even spread and
large range in the predicted formation location of the pollutants suggests that
pollutants arrive in white dwarf atmospheres with a roughly equal efficiency
from a wide range of radial locations. Ratios of elements with different
condensation temperatures such as Ca/Mg, Na/Mg, and O/Mg distinguish between
different formation temperatures, whilst pairs of ratios of siderophilic and
lithophilic elements such as Fe/Mg, Ni/Mg and Al/Mg, Ca/Mg distinguish between
temperature dependent trends and geological trends.
