Atmosphere of the Moon
The atmosphere of the Moon is a very scant presence of gases surrounding the
Otherwise, the Moon is considered not to have an atmosphere because it cannot absorb measurable quantities of radiation, does not appear layered or self-circulating, and requires constant replenishment due to the high rate at which its gases are lost into space.Roger Joseph Boscovich was the first modern astronomer to argue for the lack of atmosphere around the Moon in his De lunae atmosphaera (1753).
Sources
One source of the lunar atmosphere is outgassing: the release of gases such as radon and helium resulting from radioactive decay within the crust and mantle. Another important source is the bombardment of the lunar surface by micrometeorites, the solar wind, and sunlight, in a process known as sputtering.[7]
Escape velocity and atmospheric hold
Gases can:
- be re-implanted into the regolith as a result of the Moon's gravity;
- escape the Moon entirely if the particle is moving at or above the lunar escape velocity of 2.38 km/s (1.48 mi/s), or 5,328 mph (8,575 km/h);
- be lost to space either by solar radiation pressure or, if the gases are ionized, by being swept away in the solar wind's magnetic field.
Composition
What little atmosphere the Moon has consists of some unusual gases, including sodium and potassium, which are not found in the atmospheres of Earth, Mars, or Venus. At sea level on Earth, each cubic centimeter of the atmosphere contains approximately 1019 molecules; by comparison the lunar atmosphere contains fewer than 106 molecules in the same volume. On Earth, this is considered to be a very good vacuum. In fact, the density of the atmosphere at the Moon's surface is comparable to the density of some of the outermost fringes of Earth's atmosphere, where the International Space Station orbits.[8]
The elements sodium and potassium have been detected in the Moon's atmosphere using Earth-based
The average daytime abundances of the elements known to be present in the lunar atmosphere, in atoms per cubic centimeter, are as follows:
- Argon: 20,000–100,000[11]
- Helium: 5,000–30,000[11]
- Neon: up to 20,000[11][12]
- Sodium: 70
- Potassium: 17
- Hydrogen: fewer than 17
This yields approximately 80,000 total atoms per cubic centimeter, marginally higher than the quantity posited to exist in the atmosphere of Mercury.[10] While this greatly exceeds the density of the solar wind, which is usually on the order of just a few protons per cubic centimeter, it is virtually a vacuum in comparison with the atmosphere of the Earth.
The Moon may also have a tenuous "atmosphere" of electrostatically levitated dust. See Lunar soil for more details.
Ancient atmosphere
In October 2017,
See also
- Atmosphere of Mercury
- Exosphere
- Lunar Atmosphere and Dust Environment Explorer (LADEE)
- Orders of magnitude (pressure)
- Sodium tail of the Moon
References
- ^ "Lunar horizon glow from Surveyor 7". The Planetary Society. May 6, 2016. Retrieved Aug 8, 2022.
- ^ "NASA Mission To Study Mysterious Lunar Twilight Rays". Science Mission Directorate. Sep 3, 2013. Retrieved Aug 8, 2022.
- . Retrieved 2022-08-08.
- ^ Deborah Byrd (Apr 24, 2014). "The zodiacal light, seen from the moon". EarthSky. Retrieved Aug 8, 2022.
- ^ Williams, David R. "Moon Fact Sheet". NASA. Retrieved 16 November 2016.
- ^ Globus, Ruth (1977). "Chapter 5, Appendix J: Impact Upon Lunar Atmosphere". In Johnson, Richard D.; Holbrow, Charles (eds.). Space Settlements: A Design Study. NASA. NASA SP-413. Archived from the original on 2010-05-31. Retrieved 2016-11-15.
- .
- ^ "Is There an Atmosphere on the Moon?". NASA. 12 April 2013.
- .
- ^ S2CID 10406165.
- ^ .
Neon was detected over the nightside at levels comparable to He and was found to exhibit the spatial distribution of a surface accommodated noncondensable gas.
- ^ Steigerwald, William A. (17 August 2015). "NASA's LADEE Spacecraft Finds Neon in Lunar Atmosphere". NASA. Retrieved 18 August 2015.
- ^ Ciaccia, Chris (July 24, 2018). "Life on the Moon? New study argued life could have existed on the lunar surface". Fox News.
- ^ "NASA: The Moon Once Had an Atmosphere That Faded Away". Time. Retrieved 16 April 2018.
This article incorporates public domain material from Is There an Atmosphere on the Moon?.