On 15 August 1977, a radio telescope in Ohio picked up a narrow, powerful signal from the direction of Sagittarius. Astronomer Jerry Ehman circled the characters on the printout and wrote "Wow!" in the margin. Despite decades of searching, it has never been heard again. Nothing points to an alien origin, and natural explanations have since been proposed.
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.