Recognizing Martians: If We Find ET, Will We Know?

As NASA prepares to set twin robots loose on the Martian surface and makes plans to send another in 2007, the agency’s long term goal is clear: Determine whether the red planet does or ever did harbor life. But the current search for life is necessarily limited to life as we know it, organisms dependent on liquid water. A reader recently suggested that “we as humans are arrogant, simply believing that any other form of life will be just like us.”