On Earth, gravity holds some of your body fluids down in your legs. In space, about two liters shift toward the upper body within the first days. Astronauts call it puffy face, bird legs syndrome. Their noses get stuffy, like a never-ending cold, and the extra pressure in the head can even change their eyesight.
A large share of Earth's water molecules formed in the interstellar cloud that existed before the Sun was even born, more than 4.6 billion years ago. You are literally drinking a cosmic fossil.
By day, the Martian sky looks butterscotch because of fine dust hanging in the air. But at dusk, those same grains scatter blue light forward, creating a bluish glow around the Sun. Rovers have photographed these blue sunsets: the exact reverse of what we see on Earth.