Testing interplanetary transfer of bacteria between Earth and Mars as a result of natural impact phenomena and human spaceflight activities

Interplanetary transport of microbes between Earth and Mars can be envisioned to occur either naturally as a consequence of impacts (lithopanspermia) or as a result of human and robotic spaceflight. In either case, the considerations for modeling successful transfer of microbial life are similar. The probability of microbes surviving either natural or human-mediated transfer is a function of: the initial population size and composition (i.e., the bioload); survival of launch, transit through space, entry and deposition; and ability to survive and proliferate on the recipient planet. Modeling this process for testing lithopanspermia and for mitigation of forward and back contamination for planetary protection purposes calls for accurate simulation of all aspects of transfer.