Even though we have satellite imagery and programs like google earth, there are still creatures out there that we have not discovered. how is this possible?

A lot of the organisms we haven't discovered are bacteria and really really small organisms that can't be seen by google earth, only under a microscope. Also there are a lot more organisms living in the depths of the sea that we don't have the technology to find. 

Google that man, you don't need to use look for synonyms of critical, but that info should be in the defenition.