When we send missions to other planets like Mars, there are multiple objectives like studying the chemical composition of the surface soil, the physical structure of the planet etc... The most important of them being detection of life. Though there is communication between the Probe and the command centre on earth, the signal is not strong enough to stream video. Hence, the machine will have to be given rules based on which it can detect life.
The fundamental based on which the rules were framed was Entropy or the degree of disorderliness. The scientists decided that one thing which was common across all forms of life on earth was that the Entropy of these life forms was lower than the entropy of the environment. Now for one to detect order or disorder, there must be a definition of order. This is where the validity of the Probe's findings are doubtable because the order which the Probe is going to look for is something we have defined.
There might be forms of order which we might not have even imagined. So in effect we are sending a mission to an alien planet to detect forms of life which are similar to those on this planet. This is an unavoidable mistake because life adapts to the environment and hence a different environment like that of a planet like Mars would have forms of life which display forms of order different from that on the Earth.