[Oberon]

I wonder, myself. Mars represents the bottom of a very deep gravity well, and the Earth is at the bottom of an even deeper one. How could a rock get from one place to the other, and how could it get there in such a manner that evidence of life on or in the rock was not obliterated?

[RightWhale]

A rock could be blasted off Mars and get to earth 10 times easier than from earth to Mars.

[aruanan]

I wonder, myself. Mars represents the bottom of a very deep gravity well, and the Earth is at the bottom of an even deeper one. How could a rock get from one place to the other, and how could it get there in such a manner that evidence of life on or in the rock was not obliterated?

A big asteroid impact will cause some ejecta to be kicked out into space.

[Dataman]

The big mystery about the search for life outside of our planet is this:

We search the heavens for patterns in radio waves assuming there will be intelligence behind those patterns. We look in rocks for patterns that remind us of bacteria or something similar to life on earth. But we look at DNA which is certainly a pattern with a massive amount of data and do not assume an intelligence behind it. We claim that evolved life is a product of random chance yet search rocks for similarities.

Scientific schizophrenia lives. A little logic, if applied, would go a long way.