A rock hits mars. It somehow smashes martian rocks into space. Those rocks float through the vast emptiness of space and somehow hit a tiny target in the darkness called Earth. Humans stumble on one of these rocks and even though they've never been to Mars or held a Martian rock before they decide it came from the red planet. Not only that but human scientist look long and hard at the rock until they see water under the surface of Mars.
Look, I don't doubt that Mars has liquid water. I've seen pictures of the surface of Mars with signs of it. I just don't like that scientists like to make definitive statements about implausible objects.
At the very least I'd like the science community and those that report on science to keep the phrase "maybe, maybe not" in their head while thinking up outlandish ideas.
