Seeding the Solar System from Earth: Mechanisms, Survival, and Implications of Terrestrial Lithopanspermia

The hypothesis that life can be transferred between planetary bodies, known as lithopanspermia, has traditionally considered Earth as a recipient of extraterrestrial material. However, Earth itself may also act as a source of biological material, exporting molecules and even microorganisms to space via two main mechanisms: (i) escape of atmospheric ions and possibly organic fragments from the upper atmosphere, and (ii) ejection of rock fragments by large impacts. In this article, we review the evidence from space missions, laboratory experiments, and dynamical models that bear on the possibility of terrestrial material reaching other bodies in the Solar System, and identify the physical filters — atmospheric filtering of ejecta, organic-ion survival during outflow, and the compounding of survival and transfer probabilities — that constrain how efficiently this could occur. We discuss the survival of biomolecules under space conditions, the probability of transfer, and the implications for astrobiology and planetary protection. Direct detection of complex organic molecules escaping Earth is still lacking, and several of the physical filters discussed here are unconstrained by observation; the evidence supports Earth as a plausible, if comparatively minor, contributor to natural interplanetary transfer, rather than establishing that this process has occurred.