Mercury’s shorter, but still very long, days

Using the Arecibo Radio Telescope in Puerto Rico, a team of radio astronomers led by Gordon Pettengill makes the determination that Mercury rotates on its axis once every 59 Earth days, a much shorter “day” for Mercury than the previously estimated 88 Earth day rotation. Pettengill is a pioneer of radio and radar astronomy, and will go on to use both methods to study asteroids, Venus, and Earth’s moon.