My two-cents: Anthropologically speaking it is best to not contaminate the indigenous life forms one is trying to study such as by making too much of an overt presence. To announce one's presence would immediately cause the subjects one is observing to behave unnaturally. Data would immediately be skewed. I would imagine that there are general guide-lines in place that attempt to minimize unnecessary exposure to outside influences.
Of course, expeditions occasionally mess up. An occasional crash happens here or there. S#*t happens. If accidental exposure can be kept to a minimum covert observations can continue more-or-less unabated. I would imagine that as we become more technologically advanced and interstellar travel finally becomes feasible we are likely to be in for a rude awakening. An old Star Trek TNG episode "First Contact" deals with the subject of first introductions in both a poignant and humorous way. It's one of my favorite ST-TNG episodes. Here's Wikipedia's take on the plot-line: http://en.wikipedia.org/wiki/First_Contact_%28Star_Trek:_The_Next_Generation%29 http://tinyurl.com/6r5zxc2 Regards Steven Vincent Johnson www.OrionWorks.com www.zazzle.com/orionworks
