  Gravitational interactions in star-forming regions are capable of disrupting
and destroying planetary systems, as well as creating new ones. In particular,
a planet can be stolen, where it is directly exchanged between passing stars
during an interaction; or captured, where a planet is first ejected from its
birth system and is free-floating for a period of time, before being captured
by a passing star. We perform sets of direct N-body simulations of young,
substructured star-forming regions, and follow their evolution for 10 Myr in
order to determine how many planets are stolen and captured, and their
respective orbital properties. We show that in high density star-forming
regions, stolen and captured planets have distinct properties. The semimajor
axis distribution of captured planets is significantly skewed to wider orbits
compared to the semimajor axis distribution of stolen planets and planets that
are still orbiting their parent star (preserved planets). However, the
eccentricity and inclination distributions of captured and stolen planets are
similar, but in turn very different to the inclination and eccentricity
distributions of preserved planets. In low-density star-forming regions these
differences are not as distinct but could still, in principle, be used to
determine whether observed exoplanets have likely formed in situ or have been
stolen or captured. We find that the initial degree of spatial and kinematic
substructure in a star-forming region is as important a factor as the stellar
density in determining whether a planetary system will be altered, disrupted,
captured or stolen.
