Habitability of planets in star clusters via interstellar lithopanspermia

We calculate the probability that a life-bearing planetary system in a young star cluster enriches another planetary system in the same cluster. This form of lithopanspermia has so far received little attention. We explore the possible cross fertilization of planetary systems by performing direct N-body simulations of star clusters in which we launch germinated asteroids from a selected sample of 0.9–1.1 main-sequence stars. We focus on star clusters which are consistent with the Sun’s birth cluster (∼ 2500 stars in a ∼ 1 pc virialized Plummer sphere). We calculate the dynamical evolution of the star cluster, while start launching asteroids after 100 Myr to 1 Gyr to study arrival time distribution of germinated-asteroid, therewith constraining the transport time from a life-bearing planetary system to uninhabited ones. The Galactic tidal field drives the cluster’s dissolution on a time scale of a few hundred Myr. For younger clusters, the travel time for an asteroid to reach another star is smaller and the probability of reaching another star higher. We argue that the best moment to germinate multiple stars is as soon as life emerges on one of the cluster members. The asteroid travel time in this period is 10 Myr, which is sufficiently short for resilient extremophiles to survive the unfavorable interstellar conditions.