Every step you take, you’re likely walking on a world of unseen and undescribed microbial diversity. And you don’t need to head out into nature to find these usually unnoticed microscopic organisms.
There may be no bigger question than whether we are alone in our solar system. As our spacecraft find new clues about the presence of liquid water now or in the past on Mars, the possibility of some kind of life there looks more likely. On Earth, water means life, and that’s why the exploration of Mars is guided by the idea of following the water.