Carl Sagan, pioneer and hero of planetary protection standing next to model of Viking - still regarded as the gold standard for planetary protection.
When the entire biosphere hangs in the balance, it is adventuristic to the extreme to bring Martian life here. Sure, there is a chance it would do no harm; but that is not the point. Unless you can rule out the chance that it might do harm, you should not embark on such a course.Carl Sagan wrote in his book Cosmic Connection:
…Precisely because Mars is an environment of great potential biological interest, it is possible that on Mars there are pathogens, organisms which, if transported to the terrestrial environment, might do enormous biological damage - a Martian plague, the twist in the plot of H. G. Wells' War of the Worlds, but in reverse. This is an extremely grave point. On the one hand, we can argue that Martian organisms cannot cause any serious problems to terrestrial organisms, because there has been no biological contact for 4.5 billion years between Martian and terrestrial organisms. On the other hand, we can argue equally well that terrestrial organisms have evolved no defenses against potential Martian pathogens, precisely because there has been no such contact for 4.5 billion years. The chance of such an infection may be very small, but the hazards, if it occurs, are certainly very high.
…The likelihood that such pathogens exist is probably small, but we cannot take even a small risk with a billion lives.
…The likelihood that such pathogens exist is probably small, but we cannot take even a small risk with a billion lives.
RECOMMENDATION 10: Considering the global nature of the issue, consequences resulting from an unintended release could be borne by a larger set of countries than those involved in the programme.
It is recommended that mechanisms dedicated to ethical and social issues of the risks and benefits raised by an MSR are set up at the international level and are open to representatives of all countries.
from: Mars Sample Return backward contamination – Strategic advice and requirements
"the problem of risk - even extremely low risk - is exacerbated because the consequences of back contamination could be quite severe Without being overly dramatic, the consequences might well include the extinction of species and the destruction of whole ecosystems. Humans could also be threatened with death or a significant decrease in life prospects
In this situation, what is an ethically acceptable level of risk, even if it is quite low? This is not a technical question for scientists and engineers. Rather, it is a moral question concerning risk. Currently, the vast majority of the people exposed to this risk do not have a voice or a vote in the decision to accept it. Most of the literature, on back contamination is framed as a discourse among experts in planetary protection. Yet, as I've already argued, space exploration is inescapably a social endeavor done on behalf of the human race. Astronauts and all the supporting engineers and scientists work as representatives of the human race...
..In this situation, to treat persons with dignity and justice means that everyone must have an opportunity to voice their opinion concerning whether humans should accept the risk..."
from: God's preferential option for life: a Christian perspective on astrobiology