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Lunar horizon glow

Lunar horizon glow is a phenomenon due to which dust particles on the Moon's thin Atmosphere create a glow during lunar sunset. The Surveyor program provided data and photos of the phenomenon, Astronauts in the Apollo 15, and Apollo 17 missions observed them while in lunar orbit.

Lunar Horizon Glow as observed by Surveyor 7 mission.
The thin lunar atmosphere is visible on the Moon's surface at sunrise and sunset with the lunar horizon glow[1] and lunar twilight rays, like Earth's crepuscular rays. This Apollo 17 sketch by Eugene Cernan depicts the glow and rays[2] among the general zodiacal light.[3][4]

Cause edit

Dust kicked off from the surface of the Moon will stay in the atmosphere for around 3 hours. Apart from this, electrically charged particles could be levitated by electrostatic fields with a strength of >500 V cm−1.[5] This cloud of dust, near the lunar terminator line, forward scatters the light, creating a glow near the horizon during lunar sunset. The dust, 10 micrometer in diameter, is thought to be above 10 km from the lunar surface. The levitation mechanism is thought to eject 10^7 more particles per unit time into the cloud than could micro meteorites. The term "Moon fountain" has been used to describe this effect.

During lunar day, infrared rays and ultraviolet rays from the Sun are strong enough to knock electrons off the dust present on lunar surface. These positively charged particles get repelled from the surface kilometers high. On the night side, the dust is negatively charged by electrons from the solar wind. Particles at the night side achieve greater electrical tension differences than the day side, launching dust particles to even higher altitudes.[6] This dust eventually falls back to the surface, and the cycle repeats.[7]

In celestial bodies without any significant atmosphere, electrostatic transport is believed to be the leading cause of dust transport. Laboratory experiments show that dusty surfaces tend to become smooth as a result of dust mobilization. This phenomenon is thought to explain the process of dust ponds in the asteroids 433 Eros and comet 67P/Churyumov–Gerasimenko.[8]

Strange glowing lights on the Moon are recorded from Earth for centuries. This phenomenon, known as "transient lunar phenomena", is now generally accepted to be visible evidence of meteoroids impacting the lunar surface. But others with a amorphous reddish or whitish glows or even as dusky hazy regions that change shape or disappear over seconds or minutes, are thought to be because of sunlight reflecting from suspended lunar dust.

In 1956, this effect was anticipated by science fiction author Hal Clement in his short story "Dust Rag", published in Astounding Science Fiction.[6]

Exploration edit

Coronal photographs of the Moon from Apollo 15 and 17 showed excessive brightness. The glow was also observed by Astronauts in lunar orbit during sunrise for about 10 seconds. Such rays were also reported by astronauts aboard Apollo 8, and 10. These might have been similar to crepuscular rays on Earth.[6] The glow is also believed to appear in the star tracker data from the Clementine mission although it will be masked by Coronal and Zodiacal light. The Apollo missions placed laser retroreflectors on the lunar surface. The dust is believed to be the cause of the degradation of the instruments. Apollo 17 also placed an experiment on the Moon's surface called LEAM (Lunar Ejecta and Meteorites). It looked for dust kicked up by small meteoroids hitting the Moon's surface, and recorded the speed, energy, and direction of tiny particles. LEAM saw a large increase in number of particles every morning, coming from the east or west—rather, and slower than speeds expected for lunar ejecta. The experiment's temperature increased to near 100 degrees Celsius a few hours after each lunar sunrise, so the unit had to be turned off temporarily to prevent overheating. It is thought that this is a result of electrically charged moondust sticking to LEAM, darkening its surface so the experiment package absorbed rather than reflected sunlight. Scientists were unable to make a definite explanation of the problem, as LEAM operated only briefly before the Apollo program ended.[9]

 
Clementine mission star tracker image of Moon and Venus

During the Lunar Reconnaissance Orbiter mission, scientists performed experiments with the Lunar Reconnaissance Orbiter Camera (LROC), on 20 July 2011 to attempt to detect a weak signal of LHG. The experiment was done jointly with the Lyman-Alpha Mapping Project (LAMP), LRO narrow angle camera and wide angle camera. Both of these captured pictures at high exposure times, almost 50 times larger than their normal. During the experiment LRO was positioned in a way that it shadowed the Sun by the Moon and was looking back across Space to observe material. The NAC found a glow of 0.03 DN, and the LHG found a glow of 0.2 DN. A spectral radiance of 0.01 W/m2/sr/um was predicted to be detected by the NAC. So for the given observing geometry, the LHG, must be dimmer than 0.01 W/m2/sr/um.

See also edit

References edit

  1. ^ "Lunar horizon glow from Surveyor 7". The Planetary Society. May 6, 2016. from the original on August 8, 2022. Retrieved Aug 8, 2022.
  2. ^ "NASA Mission To Study Mysterious Lunar Twilight Rays". Science Mission Directorate. Sep 3, 2013. from the original on July 3, 2022. Retrieved Aug 8, 2022.
  3. ^ Colwell, Joshua E.; Robertson, Scott R.; Horányi, Mihály; Wang, Xu; Poppe, Andrew; Wheeler, Patrick (2009-01-01). "Lunar Dust Levitation - Journal of Aerospace Engineering - Vol 22, No 1". Journal of Aerospace Engineering. 22 (1): 2–9. doi:10.1061/(ASCE)0893-1321(2009)22:1(2). from the original on 2022-08-08. Retrieved 2022-08-08.
  4. ^ Deborah Byrd (Apr 24, 2014). "The zodiacal light, seen from the moon". EarthSky. from the original on August 8, 2022. Retrieved Aug 8, 2022.
  5. ^ Stubbs, Timothy J.; Richard R. Vondrak & William M. Farrell (2005). "A Dynamic Fountain Model for Lunar Dust" (PDF). Lunar and Planetary Science XXXVI. (PDF) from the original on 2019-02-01. Retrieved 2023-10-15.
  6. ^ a b c . NASA. Archived from the original on 19 March 2010.
  7. ^ . NASA. Archived from the original on 2021-11-14. Retrieved 2023-10-15.
  8. ^ "Dust 'floats' above lunar surface—electrostatic dust transport reshapes surfaces of airless planetary bodies". Phys.org. from the original on 13 July 2023. Retrieved 28 September 2023.
  9. ^ Bell, Trudy E. (September 2006). "Stronger Than Dirt". Air & Space Smithsonian: 46–53. from the original on 2021-10-19. Retrieved 2023-10-15.

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Lunar horizon glow is a phenomenon due to which dust particles on the Moon s thin Atmosphere create a glow during lunar sunset The Surveyor program provided data and photos of the phenomenon Astronauts in the Apollo 15 and Apollo 17 missions observed them while in lunar orbit Lunar Horizon Glow as observed by Surveyor 7 mission The thin lunar atmosphere is visible on the Moon s surface at sunrise and sunset with the lunar horizon glow 1 and lunar twilight rays like Earth s crepuscular rays This Apollo 17 sketch by Eugene Cernan depicts the glow and rays 2 among the general zodiacal light 3 4 Contents 1 Cause 2 Exploration 3 See also 4 ReferencesCause editDust kicked off from the surface of the Moon will stay in the atmosphere for around 3 hours Apart from this electrically charged particles could be levitated by electrostatic fields with a strength of gt 500 V cm 1 5 This cloud of dust near the lunar terminator line forward scatters the light creating a glow near the horizon during lunar sunset The dust 10 micrometer in diameter is thought to be above 10 km from the lunar surface The levitation mechanism is thought to eject 10 7 more particles per unit time into the cloud than could micro meteorites The term Moon fountain has been used to describe this effect During lunar day infrared rays and ultraviolet rays from the Sun are strong enough to knock electrons off the dust present on lunar surface These positively charged particles get repelled from the surface kilometers high On the night side the dust is negatively charged by electrons from the solar wind Particles at the night side achieve greater electrical tension differences than the day side launching dust particles to even higher altitudes 6 This dust eventually falls back to the surface and the cycle repeats 7 In celestial bodies without any significant atmosphere electrostatic transport is believed to be the leading cause of dust transport Laboratory experiments show that dusty surfaces tend to become smooth as a result of dust mobilization This phenomenon is thought to explain the process of dust ponds in the asteroids 433 Eros and comet 67P Churyumov Gerasimenko 8 Strange glowing lights on the Moon are recorded from Earth for centuries This phenomenon known as transient lunar phenomena is now generally accepted to be visible evidence of meteoroids impacting the lunar surface But others with a amorphous reddish or whitish glows or even as dusky hazy regions that change shape or disappear over seconds or minutes are thought to be because of sunlight reflecting from suspended lunar dust In 1956 this effect was anticipated by science fiction author Hal Clement in his short story Dust Rag published in Astounding Science Fiction 6 Exploration editCoronal photographs of the Moon from Apollo 15 and 17 showed excessive brightness The glow was also observed by Astronauts in lunar orbit during sunrise for about 10 seconds Such rays were also reported by astronauts aboard Apollo 8 and 10 These might have been similar to crepuscular rays on Earth 6 The glow is also believed to appear in the star tracker data from the Clementine mission although it will be masked by Coronal and Zodiacal light The Apollo missions placed laser retroreflectors on the lunar surface The dust is believed to be the cause of the degradation of the instruments Apollo 17 also placed an experiment on the Moon s surface called LEAM Lunar Ejecta and Meteorites It looked for dust kicked up by small meteoroids hitting the Moon s surface and recorded the speed energy and direction of tiny particles LEAM saw a large increase in number of particles every morning coming from the east or west rather and slower than speeds expected for lunar ejecta The experiment s temperature increased to near 100 degrees Celsius a few hours after each lunar sunrise so the unit had to be turned off temporarily to prevent overheating It is thought that this is a result of electrically charged moondust sticking to LEAM darkening its surface so the experiment package absorbed rather than reflected sunlight Scientists were unable to make a definite explanation of the problem as LEAM operated only briefly before the Apollo program ended 9 nbsp Clementine mission star tracker image of Moon and Venus During the Lunar Reconnaissance Orbiter mission scientists performed experiments with the Lunar Reconnaissance Orbiter Camera LROC on 20 July 2011 to attempt to detect a weak signal of LHG The experiment was done jointly with the Lyman Alpha Mapping Project LAMP LRO narrow angle camera and wide angle camera Both of these captured pictures at high exposure times almost 50 times larger than their normal During the experiment LRO was positioned in a way that it shadowed the Sun by the Moon and was looking back across Space to observe material The NAC found a glow of 0 03 DN and the LHG found a glow of 0 2 DN A spectral radiance of 0 01 W m2 sr um was predicted to be detected by the NAC So for the given observing geometry the LHG must be dimmer than 0 01 W m2 sr um See also editDust ponds Atmosphere of the Moon Lunar soilReferences edit Lunar horizon glow from Surveyor 7 The Planetary Society May 6 2016 Archived from the original on August 8 2022 Retrieved Aug 8 2022 NASA Mission To Study Mysterious Lunar Twilight Rays Science Mission Directorate Sep 3 2013 Archived from the original on July 3 2022 Retrieved Aug 8 2022 Colwell Joshua E Robertson Scott R Horanyi Mihaly Wang Xu Poppe Andrew Wheeler Patrick 2009 01 01 Lunar Dust Levitation Journal of Aerospace Engineering Vol 22 No 1 Journal of Aerospace Engineering 22 1 2 9 doi 10 1061 ASCE 0893 1321 2009 22 1 2 Archived from the original on 2022 08 08 Retrieved 2022 08 08 Deborah Byrd Apr 24 2014 The zodiacal light seen from the moon EarthSky Archived from the original on August 8 2022 Retrieved Aug 8 2022 Stubbs Timothy J Richard R Vondrak amp William M Farrell 2005 A Dynamic Fountain Model for Lunar Dust PDF Lunar and Planetary Science XXXVI Archived PDF from the original on 2019 02 01 Retrieved 2023 10 15 a b c Moon Fountains NASA Archived from the original on 19 March 2010 The Moon and the Magnetotail NASA Archived from the original on 2021 11 14 Retrieved 2023 10 15 Dust floats above lunar surface electrostatic dust transport reshapes surfaces of airless planetary bodies Phys org Archived from the original on 13 July 2023 Retrieved 28 September 2023 Bell Trudy E September 2006 Stronger Than Dirt Air amp Space Smithsonian 46 53 Archived from the original on 2021 10 19 Retrieved 2023 10 15 Retrieved from https en wikipedia org w index php title Lunar horizon glow amp oldid 1210121825, wikipedia, wiki, book, books, library,

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