PlanetsDiscusses the planets and the broad areas of disagreement existing about their origin, composition, atmospheres and surfaces; also looks at the possibility of life on other planets. |
Common terms and phrases
ammonia approx areas astronauts astronomers atmos believed belt billion carbon dioxide Century charged particles civilization clouds color comets contain cool Copernicus core craters crust dark detected distance dust earth earth's atmosphere earthly emit erosion evolved gases gravitation Greeks heat helium hydrogen infrared instruments interior ionosphere Jupiter Jupiter's known land layer liquid lunar magnetic field mantle Mare Imbrium Mariner Mars Martian mass material Mercury meteorite methane miles in diameter million miles modern molecules moon moon's surface mosphere motion mountains moving mysterious Neptune Observatory observed ocean orbit organisms oxygen pass picture planet planetary Pluto probably radar radiation radio telescopes radio waves radio window rays Red Spot reflected rings rocks rotation satellites Saturn scientists seen solar system solid space spacecraft speed sphere stars sun's sunlight temperature tion ultraviolet light universe Uranus Venus visible light water vapor wavelengths zone