Sixty-six million years ago, an asteroid about 10 km wide struck Earth, gouging a crater roughly 180 km across. Fires, dust and aerosols darkened the sky and collapsed ecosystems: about three in four species vanished. Birds, the direct descendants of dinosaurs, were among the survivors.
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.