Since there are Mars rocks on Earth, there are surely Earth rocks on Mars (even if it is a bit harder to get off Earth than Mars.)

Some of those Earth rocks had bacteria inside them. The only question is how many survived the trip, and what happened once they got there.

By the start of 2033, will there be consensus that there has ever been life on Mars that was not brought there by humans?, 8k, beautiful, illustration, trending on art station, picture of the day, epic composition