In 1967, PhD student Jocelyn Bell spotted a radio signal pulsing every 1.3 seconds with clockwork regularity. Her team jokingly labelled it LGM-1, for "Little Green Men". It turned out to be a spinning neutron star, sweeping its beam across space like a lighthouse. The 1974 Nobel Prize went to her supervisor, but not to her.
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.