Unrestricted Earth Return, Planetary Protection and the Wisdom of the Precautionary Principle

We live in a new era of space exploration where robotic spacecraft can be sent out to deep space and retrieve samples of our moon, planets, and icy moons for direct return to Earth. These sample return missions are now mounted by diverse international space agencies as well as private industry, but without international planetary protection protocols necessary to prevent a back contamination event involving any alien microbes. The organizations that allow for these missions (Category V) to proceed are the Committee on Space Research (COSPAR) and the Space Studies Board (SSB), which has been allowing Unrestricted Earth Return (hereafter UER) from samples of Small Solar System Bodies such as comets and asteroids. These samples are brought directly to Earth-based laboratories for study without any of them being certified to handle harmful or deadly pathogenic organisms if these are found. Although little is decisively known about the potential of comet and asteroid samples to contain harmful pathogens, the decision to allow UER’s is based on the “assumption” based on a possibly incorrect scientific opinion that comets and asteroids are indeed dead lifeless objects. The rationale for this assumption is centered on the estimated 4700 metric tons of Interplanetary Dust Particles (IDP’s) from comets and asteroids that settle to the surface of Earth each year without having any substantial evidence of adverse global effects that we are aware of and therefore is considered “biosphere safe”. But is it? We ourselves have good reason to challenge this assertion. Moreover, SSB recommendations point out that while the risk of back contamination from UER missions is very low, it is not zero.