Mercury (planet) Mercury (planet) Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 87.97 days is the shortest of all the planets in the Solar System. It is named after the Roman deity Mercury, the messenger of the gods. Like Venus, Mercury orbits the Sun within Earth's orbit as an "inferior planet", and never exceeds 28° away from the Sun. When viewed from Earth, this proximity to the Sun means the planet can only be seen near the western or eastern horizon during the early evening or early morning. At this time it
The Secret of the Ninth Planet The Secret of the Ninth Planet The Secret of the Ninth Planet is a science-fiction novel written by Donald A. Wollheim and first published in the United States in 1959 by the John C. Winston Co. Wollheim takes his heroes on a grand tour of the solar system as that team struggles to prevent an alien force from blowing up the sun. This is the last of three juvenile novels that Wollheim wrote for Winston, the other two being "The Secret of Saturn's Rings" and "The Secret of the Martian Moons". This is one of the thirty-five juvenile novels that