I was watching another alien invasion movie today. And I feel that this whole Martians/venusians or Alpha centaurians are vulnerable is a big problem with the whole genre. I believe that no civilization can really discover space travel without first discovering the secrets of health and disease. And if they have discovered that, then it is only a matter of time before they realize that they dont need huge machines and energy expensive robots and exoskeletons etc. All that they will do is send an earth-rover initially equipped with a small biological specimen collector/analyzer and find out the genetic makeup of earthlings. Once they do that, they will obviously realize that humans are susceptible to a lot of diseases. They dont need to understand english, they dont need to communicate with us (who the hell except us wants to anyway ?). It is our (rather Hollywood's) stupidity to think that Aliens would come to Earth and stand before us and in a comma...