Intergalactic space is staggeringly empty: on average, around one atom per cubic metre. The air you breathe holds about 25 trillion trillion molecules in the same volume. Even the best laboratory vacuums are millions of times fuller. And yet this thin gas, spread across vast distances, holds a large share of the Universe's ordinary matter.
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.