Excellent link,
tzb57r!
We may be facing this sort of ethical dilemma in the near future, if non-intelligent life is discovered on Mars;
As it says in that link, there is no NASA policy or international protocol yet concerning the discovery of extraterrestrial life; soon we may need one.
That page contains further links to two fascinating PDF'S considering the situation from a moral and scientific standpoint;
http://www.seti.org/pdf/m_race_guidelines.pdf
http://www.seti-inst.edu/pdf/m_race_ethics.pdf
Three axioms defined in one of these links are of interest; faced with the discovery of extraterrestrial life of any kind, the most important considerations are considered to be the
Preservation, Stewardship and
Intrinsic Worth of the lifeforms concerned.
Some however consider that the preservation of extraterrestrial lifeforms, intelligent or non-intelligent, should be subordinate to the propagation of Terrestrial species and civilisation; it is important to remember that the expansion of terrestrial life into the universe is a respectable aim. If we find lifeforms on every terrestrial type planet this aim will be difficult to achieve without disturbing such lifeforms.
For this reason the policies of Preservation and Stewardship should be observed as far as possible, but if it is possible to remove any primitive ecosystems from a planet and preserve them in smaller, tailor-made environments, preservation could be possible while allowing the planet concerned to be developed for terrestrial life.
This procedure would certainly not be correct in the case of the discovery of intelligent extraterrestrial life; any such society should be disturbed as little as possible, while being closely observed and recorded;
eventually it should be contacted and exposed to the full complexity of our terrestrial civilisation (whatever that may be like at the time);
but I am of the opinion that a series of representative samples of the local intelligent race should be extracted prior to that contact, and exposed to terrestrial culture at full strength to produce a group of beings capable of crosscultural interpretation.
This process could go on for decades or millenia before full contact is made.
This idea is partly based on the imaginings of present-day UFO 'contactees'; the strategy allegedly followed by the imaginary aliens in the equally imaginary flying saucers would be a sensible one, if they didn't keep allowing themselves to be 'seen'. Hopefully future human explorers wouldn't make such a pig's breakfast of such an important issue.