Catalyzed Lithopanspermia Through Disk Capture of Biologically Active Interstellar Material

During the dynamical evolution of a planetary system, dust grains, rocks, planetesimals, and even planets can be ejected from the system. Ejected planetesimals become part of the interstellar medium (ISM) and can randomly encounter other stellar systems. In case a planetary system hosts biologically active material, a fraction of the ejected planetesimals may still harbor living organisms and/or other biotic/pre-biotic elements. It was suggested that such biologically active ISM-rocks/planetesimals, if captured in another planetary system, could provide the basic “seeds” for the development of life in this new system. Studies of the exchange of such potential life-seeds, termed lithopanspermia, has shown it to be inefficient, and rare, given the low-probability for the capture of such ISMplanetesimals. Here, we suggest a novel and potentially more efficient channel for lithopanspermia through disk-capture of ISM-planetesimals. We find that ISMplanetesimals crossing a young protoplanetary disk can dissipate energy via gas drag and become embedded in their new protoplanetary disk. Our results show that planetesimals below ≤1m are efficiently captured. It was suggested that biologically active material can survive interstellar travel inside rocks of at least 10 kg in mass. We find that during the protoplanetary disk’s lifetime, 1013 − 1016 rocks/planetesimals larger than this threshold can be captured by a typical young planetary system. This lithopanspermia channel could therefore give rise to high rates of exchange of living organisms and/or other biotic/pre-biotic elements between planetary systems, much higher than suggested by other channels.