  The collision history of asteroids is an important archive of inner Solar
System evolution. Evidence for these collisions is brought to Earth by
meteorites, which can preserve impact-reset radioisotope mineral ages. However,
as meteorites often preserve numerous mineral ages, their interpretation is
controversial. Here, we combine analysis of phosphate U-Pb ages and mineral
microtextures to construct a collision history for the highly shocked
Chelyabinsk meteorite. We show that phosphate U-Pb ages in the meteorite are
independent of thermal history at macro-to-microscales, correlating instead
with phosphate microtexture. Isotopic data from pristine phosphate domains is
largely concordant, whereas fracture-damaged domains universally display
discordance. Combining both populations best constrains upper (4,473 +/- 11 Ma)
and lower intercept (-9 +/- 55 Ma, i.e., within error of the present day) U-Pb
ages for Chelyabinsk phosphates. We conclude that all phosphate U-Pb ages were
completely reset during an ancient high energy collision. Fracture-damaged
phosphate domains experienced further Pb-loss during mild collisional heating
in the geologically recent past, and must be targeted to properly constrain a
lower intercept age. Targeting textural sub-populations of phosphate grains can
significantly improve the calculation and interpretation of U-Pb ages,
permitting more robust reconstruction of both ancient and recent asteroidal
collision histories.
