While the common wisdom that the moon lacks an atmosphere has been part of general knowledge for years, a NASA document released in January 2014 indicates that the moon does have an atmosphere with gases like potassium and sodium which do not appear in the atmosphere of Venus, Mars or Earth. The atmosphere on the moon has much less gas in it; on Earth, the sea-level atmosphere has 10 quintillion molecules per cubic centimeter, while that same cubic centimeter only has 1 million molecules on the moon. So while the lunar atmosphere is quite thin, it nevertheless exists.
The Apollo 17 mission used the Lunar Atmospheric Composition Experiment on the lunar surface to analyze what the air was actually like on the moon. This study found minuscule amounts of several different types of molecules and atoms, such as argon, helium and possibly ammonia, carbon dioxide, neon and methane. Researchers on Earth using telescopes designed to block lunar light have captured images of the glow that the potassium and sodium atoms create when they receive energy from the sun. These gases likely came from solar wind particles and high-energy photons, as well as surface material evaporation, material grabbed from meteoroid and comet impact, and gas come from the interior of the moon.Learn More
The moon has a total of eight individual phases. Four of these phases are considered to be the moon's main phases. The remaining four phases are considered to be the moon's transitional phases.Full Answer >
The way to identify which of the phases the moon is in is based on which section of the moon's face is lit by the sun. The moon has eight phases, which happen in the same cycle over the course of a 29-day period.Full Answer >
Half of the moon is always lit by the sun, unless the sun is eclipsed by the Earth. The portion of the illuminated moon viewed from Earth depends on the moon's orbit. As the moon orbits, different portions of shadow and illumination are seen from Earth, creating the moon's phases.Full Answer >
The moon orbits Earth about once every 27.322 days. Viewed from Earth, the moon's orbit is nearly a perfect circle tilted approximately 5 degrees to Earth's orbit. Due to tidal forces, the same side of the moon always faces Earth, so it also rotates about once every 27.322 days.Full Answer >