Comparing the planets

The planets fall into two main groups, and their orbits differ as well: distance from the Sun and orbital period both increase outward, from Mercury's 88-day year to Neptune's roughly 165-year orbit, and all eight orbit in nearly the same plane and in the same direction. The inner, terrestrial planets, Mercury, Venus, Earth, and Mars, are small, dense, and rocky, with few or no moons: Mercury has almost no atmosphere, Venus has a thick carbon dioxide atmosphere whose greenhouse effect makes it the hottest planet at about 460 degrees Celsius, Earth is the only planet with liquid water on its surface and active plate tectonics, and Mars has a thin, cold carbon dioxide atmosphere and no global magnetic field. The outer, giant planets are much larger and have no solid surface: Jupiter and Saturn are gas giants made mostly of hydrogen and helium, while Uranus and Neptune are ice giants rich in water, ammonia, and methane. All four giants have rings and many moons, and Jupiter has the strongest magnetic field of any planet. Planets also differ in rotation: Venus spins slowly backward, with a day longer than its year, and Uranus is tipped on its side. Some moons are geologically active too; Jupiter's moon Io is the most volcanically active body known.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report