Some time ago there was an article in The Republic about scientists finding a rock from Mars here on Earth. How do they know that it did not come from somewhere else in the universe or from anywhere in our solar system? I can’t see how it can be anything but a wild guess.
It is true that every now and again, they find rocks from Mars here at home. Mostly they find them in places like Antarctica, not because Antarctica is especially prone to getting hit by rocks from outer space, but because it’s easier to find them there. There aren’t a lot of trees or underbrush or buildings or stuff to cover them up.