  The proposition that life can spread from one planetary system to another
(interstellar panspermia) has a long history, but this hypothesis is difficult
to test through observations. We develop a mathematical model that takes
parameters such as the microbial survival lifetime, the stellar velocity
dispersion, and the dispersion of ejecta into account in order to assess the
prospects for detecting interstellar panspermia. We show that the correlations
between pairs of life-bearing planetary systems (embodied in the
pair-distribution function from statistics) may serve as an effective
diagnostic of interstellar panspermia, provided that the velocity dispersion of
ejecta is greater than the stellar dispersion. We provide heuristic estimates
of the model parameters for various astrophysical environments, and conclude
that open clusters and globular clusters appear to represent the best targets
for assessing the viability of interstellar panspermia.
