When a coin comes out tails ten times in a row, you’ll bet on it being rigged strictly depending on your prior belief about how much you expect it to be rigged. Evidence only makes sense given your prior belief, inferred from other factors. If I hear a report of a devastating hurricane, I believe it more than if the very same report stated that a nuclear bomb went off in a city, and I won’t believe it at all if it stated that the little green men have landed in front of the White House.
When a coin comes out tails ten times in a row, you’ll bet on it being rigged strictly depending on your prior belief about how much you expect it to be rigged. Evidence only makes sense given your prior belief, inferred from other factors. If I hear a report of a devastating hurricane, I believe it more than if the very same report stated that a nuclear bomb went off in a city, and I won’t believe it at all if it stated that the little green men have landed in front of the White House.
This is one of the principles of rationality I’m proud to say I discovered on my own: http://heresiology.blogspot.com/2006/01/intelligent-design-1.html
Short version: An interesting formation on earth might be a sign of human involvement, and interesting formation on mars, not so much.