The Moon's Erlanger crater is an example of a permanently shadowed crater.

A permanently shadowed crater is a depression on a body in the Solar System within which lies a point that is always in darkness.[1][2]

As of 2019, there are 324 known permanently shadowed regions on the Moon.[3] Such regions also exist on Mercury[4] and Ceres.[5]

Location

Such a crater must be located at high latitude (close to a pole) and be on a body with very small axial tilt. The Moon has an axial tilt of about 1.5°; Mercury, 0.03°;[6] and Ceres, about 4°.[7]

On the Moon, permanent shadow can exist at latitudes as low as 58°; approximately 50 permanently shadowed regions exist in the 58°- 65° latitude range for both lunar hemispheres.[8]

The cumulative area of permanently shadowed lunar regions is about 31 thousand km2; more than half of it is in the southern hemisphere.[9]

Conditions inside craters

Craters of eternal darkness might be advantageous for space exploration and colonization, as they preserve sources of water ice[10] that can be converted into drinkable water, breathable oxygen, and rocket propellant.[11] Several of such craters show indications of water ice in their interiors, including Rozhdestvenskiy[12] and Cabeus craters[13] on the Moon, and Juling Crater on Ceres.[14] Other volatiles besides water can also be trapped in such craters, such as mercury.[15] The LCROSS mission additionally found native silver and gold in permanently shadowed craters on the Moon, probably brought there by electrostatic dust transport, and some inconclusive evidence for platinum. Gold was estimated to have a soil mass abundance of 0.52% in these craters from LCROSS data, and mercury 0.39%. This high mercury abundance has been noted as a possible health hazard of water derived from permanently shadowed craters.[16]

The craters may also contain unusually high concentrations of helium-3.[17]

A business case analysis indicates that mining of propellants in the craters could become a profitable commercial enterprise.[18]

The Moon's Shackleton Crater, as imaged by Earth-based radar

In some cases, peaks of eternal light are located nearby, that could be advantageous for solar power generation. For example, there are two peaks near Shackleton Crater that are illuminated a combined ~94% of a lunar year.[19]

Permanently shadowed regions have a stable surface temperature. On the Moon, the temperature hovers somewhere at or below 50 Kelvin.[20] Another temperatures estimate is 25 K to 70 K.[21] The low temperatures make the regions desirable locations for future infrared telescopes.[22][23]

On the other hand, computer simulations show that powerful solar storms can charge up the soil in permanently shadowed regions near the lunar poles, and may possibly produce "sparks" that could vaporize and melt the soil.[24][25]

There are other unique challenges of such regions: dark environments that restrict the ability of rovers to perceive their surroundings, cryogenic regolith that could be hard to move on, and communication interruptions.[26]

Planetary protection

In 2020, NASA assigned "sensitive location" status to the Moon's permanently shadowed regions to avoid their contamination.[27]

List

Computer renderings of some permanently shadowed regions
The south pole of the Moon
The northern hemisphere of Ceres

Below is an incomplete list of such craters:

The Moon:

Mercury:

Ceres:[39]

Research missions

Past

In 2009, LCROSS sent an impactor into a Cabeus crater, that resulted in detection of water in the ejected material.[41]

In 2012, The Lyman Alpha Mapping Project aboard NASA's Lunar Reconnaissance Orbiter has found that the permanently shadowed regions have a porous, powdery surface, that indicates the presence of water ice.[42]

In 2018, an analysis of the results of the Moon Mineralogy Mapper confirmed the existence of water ice deposits in permanently shadowed craters and crevices, with more abundance near the south pole.[43]

Current

Lunar Flashlight launched in December 2022 as a secondary payload for the Hakuto-R Mission 1 mission.[44][45]

A camera called ShadowCam has been built that is able to take high-resolution images of Permanently Shadowed Regions. It is a NASA instrument that flies on board the Korea Pathfinder Lunar Orbiter (KPLO) since 2022.[46]

Planned

The proposed International Lunar Observatory mission involves a landing near the Malapert crater.[47]

See also

References

  1. ↑ "LUNAR RECONNAISSANCE ORBITER: Permanently Shadowed Regions on the Moon" (PDF). lunar.gsfc.nasa.gov. National Aeronautics and Space Administration. Archived (PDF) from the original on 25 August 2014. Retrieved 5 December 2022.
  2. ↑ "GMS: The Moon's Permanently Shadowed Regions". 6 March 2013.
  3. ↑ "Permanently Shadowed Regions Atlas | Lunar Reconnaissance Orbiter Camera".
  4. ↑ "Permanently shadowed, radar-bright regions on Mercury".
  5. ↑ Schorghofer, Norbert; Mazarico, Erwan; Platz, Thomas; Preusker, Frank; Schröder, Stefan E.; Raymond, Carol A.; Russell, Christopher T. (2016). "The permanently shadowed regions of dwarf planet Ceres". Geophysical Research Letters. 43 (13): 6783–6789. Bibcode:2016GeoRL..43.6783S. doi:10.1002/2016GL069368.
  6. ↑ Planetary Fact Sheets, at http://nssdc.gsfc.nasa.gov
  7. ↑ Schorghofer, N.; Mazarico, E.; Platz, T.; Preusker, F.; Schröder, S. E.; Raymond, C. A.; Russell, C. T. (6 July 2016). "The permanently shadowed regions of dwarf planet Ceres". Geophysical Research Letters. 43 (13): 6783–6789. Bibcode:2016GeoRL..43.6783S. doi:10.1002/2016GL069368.
  8. ↑ Bussey, D. B. J.; Cahill, J. T. S.; McGovern, J. A.; Spudis, P. D. (1 September 2012). "A Global Catalogue of Lunar Permanently Shadowed Regions" (PDF). EPSC Abstracts. 7. Bibcode:2012epsc.conf..756B. Retrieved 5 December 2022.
  9. ↑ Crawford, Ian (2015). "Lunar Resources: A Review". Progress in Physical Geography. 39 (2): 137–167. arXiv:1410.6865. Bibcode:2015PrPhG..39..137C. doi:10.1177/0309133314567585. S2CID 54904229.
  10. ↑ "Water Ice Confirmed on the Surface of the Moon for the 1st Time!". Space.com. 21 August 2018.
  11. ↑ "Moon Mountain Seen as Prime Real Estate". www.space.com. Archived from the original on 13 February 2006. Retrieved 12 January 2022.
  12. ↑ Mitchell, Julie (2017). "Investigations of Water-Bearing Environments on the Moon and Mars". Bibcode:2017PhDT.......229M. {{cite journal}}: Cite journal requires |journal= (help)
  13. ↑ "LCROSS Mission Finds Water - Planetary News | the Planetary Society". www.planetary.org. Archived from the original on 22 January 2010. Retrieved 12 January 2022.
  14. ↑ "NASA Dawn Reveals Recent Changes in Ceres' Surface". 14 March 2018.
  15. ↑ Reed Jr., George W. (1999). "Don't drink the water". Meteoritics & Planetary Science. 34 (5): 809–811. Bibcode:1999M&PS...34..809R. doi:10.1111/j.1945-5100.1999.tb01394.x.
  16. ↑ Platts, Warren J.; Boucher, Dale; Gladstone, G. Randall (12 December 2013). "Prospecting for Native Metals in Lunar Polar Craters". 7th Symposium on Space Resource Utilization. doi:10.2514/6.2014-0338. ISBN 978-1-62410-315-5.
  17. ↑ Cocks, F. H. (2010). "3He in permanently shadowed lunar polar surfaces". Icarus. 206 (2): 778–779. Bibcode:2010Icar..206..778C. doi:10.1016/j.icarus.2009.12.032.
  18. ↑ Sowers, George F.; Dreyer, Christopher B. (2019). "Ice Mining in Lunar Permanently Shadowed Regions". New Space. 7 (4): 235–244. Bibcode:2019NewSp...7..235S. doi:10.1089/space.2019.0002. S2CID 210245597.
  19. ↑ Bussey D. B. J., McGovern J. A., Spudis P. D., Neish C. D., Noda H., Ishihara Y., Sørensen S.-A. (2010). "Illumination conditions of the south pole of the Moon derived using Kaguya topography". Icarus. 208 (2): 558–564. Bibcode:2010Icar..208..558B. doi:10.1016/j.icarus.2010.03.028.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  20. ↑ "Eternal Darkness Near the North Pole | Lunar Reconnaissance Orbiter Camera".
  21. ↑ "Casting Light on Permanently Shadowed Regions | Lunar Reconnaissance Orbiter Camera".
  22. ↑ "Liquid Mirror Telescopes on the Moon | Science Mission Directorate". Archived from the original on 2011-03-23. Retrieved 2020-08-08.
  23. ↑ "Moon Mountain Seen as Prime Real Estate". www.space.com. Archived from the original on 13 February 2006. Retrieved 12 January 2022.
  24. ↑ "Solar Storms Could Spark Soils at Moon's Poles".
  25. ↑ Jordan, A. P.; Stubbs, T. J.; Wilson, J. K.; Schwadron, N. A.; Spence, H. E.; Joyce, C. J. (2014). "Deep dielectric charging of regolith within the Moon's permanently shadowed regions". Journal of Geophysical Research: Planets. 119 (8): 1806–1821. Bibcode:2014JGRE..119.1806J. doi:10.1002/2014JE004648. S2CID 53533526.
  26. ↑ "Roving in the Permanently Shadowed Regions of Planetary Bodies". 4 December 2014.
  27. ↑ "NASA issues new guidelines to protect the Moon and Mars from Earth's germs | Business Insider India". www.businessinsider.in. Archived from the original on 2020-08-14.
  28. ↑ "Eternal Darkness Near the North Pole | Lunar Reconnaissance Orbiter Camera".
  29. ↑ "Casting Light on Permanently Shadowed Regions | Lunar Reconnaissance Orbiter Camera".
  30. ↑ Sanin, A. B.; Mitrofanov, I. G.; Litvak, M. L.; Malakhov, A.; Boynton, W. V.; Chin, G.; Droege, G.; Evans, L. G.; Garvin, J.; Golovin, D. V.; Harshman, K.; McClanahan, T. P.; Mokrousov, M. I.; Mazarico, E.; Milikh, G.; Neumann, G.; Sagdeev, R.; Smith, D. E.; Starr, R. D.; Zuber, M. T. (2012). "Testing lunar permanently shadowed regions for water ice: LEND results from LRO". Journal of Geophysical Research: Planets. 117: n/a. Bibcode:2012JGRE..117.0H26S. doi:10.1029/2011JE003971. hdl:2060/20140005994. S2CID 130773165.
  31. ↑ Sanin, A. B.; Mitrofanov, I. G.; Litvak, M. L.; Malakhov, A.; Boynton, W. V.; Chin, G.; Droege, G.; Evans, L. G.; Garvin, J.; Golovin, D. V.; Harshman, K.; McClanahan, T. P.; Mokrousov, M. I.; Mazarico, E.; Milikh, G.; Neumann, G.; Sagdeev, R.; Smith, D. E.; Starr, R. D.; Zuber, M. T. (2012). "Testing lunar permanently shadowed regions for water ice: LEND results from LRO". Journal of Geophysical Research: Planets. 117: n/a. Bibcode:2012JGRE..117.0H26S. doi:10.1029/2011JE003971. hdl:2060/20140005994. S2CID 130773165.
  32. ↑ "Moon Mountain Seen as Prime Real Estate". www.space.com. Archived from the original on 13 February 2006. Retrieved 12 January 2022.
  33. ↑ L. J. Harcke; et al. (2001). "Radar Imaging of Mercury's North and South Poles at 3.5 cm Wavelength" (PDF). Workshop on Mercury: Space Environment, Surface, and Interior (1097): 36. Bibcode:2001mses.conf...36H.
  34. ↑ J. K. Harmon; et al. (1994). "Radar mapping of Mercury's polar anomalies". Nature. 369 (6477): 213–215. Bibcode:1994Natur.369..213H. doi:10.1038/369213a0. S2CID 4320356.
  35. ↑ "Ice on Mercury". NASA. Retrieved 13 August 2016.
  36. ↑ "NASA - Eternal Darkness of Petronius Crater".
  37. ↑ New evidence for surface water ice in small‐scale cold traps and in three large craters at the north polar region of Mercury from the Mercury Laser Altimeter, Ariel N. Deutsch, Gregory A. Neumann, James W. Head. 14 September 2017. Geophysical Research Letters, Volume 44, Issue 18. doi.org/10.1002/2017GL074723
  38. ↑ "Permanently Shaded Polar Craters". NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory. 15 November 2012. Archived from the original on 30 November 2012. Retrieved 20 July 2021.
  39. ↑ Schorghofer, Norbert; Mazarico, Erwan; Platz, Thomas; Preusker, Frank; Schröder, Stefan E.; Raymond, Carol A.; Russell, Christopher T. (2016). "The permanently shadowed regions of dwarf planet Ceres". Geophysical Research Letters. 43 (13): 6783–6789. Bibcode:2016GeoRL..43.6783S. doi:10.1002/2016GL069368.
  40. ↑ "Juling Crater's Shadow". Jet Propulsion Laboratory.
  41. ↑ "LCROSS Mission Finds Water - Planetary News | the Planetary Society". www.planetary.org. Archived from the original on 22 January 2010. Retrieved 12 January 2022.
  42. ↑ "Shadows of the Moon Hide 'Fluffy' Dirt & Water Ice". Space.com. 19 January 2012.
  43. ↑ "Water Ice Confirmed on the Surface of the Moon for the 1st Time!". Space.com. 21 August 2018.
  44. ↑ "NASA is Studying How to Mine the Moon for Water". Space.com. 9 October 2014.
  45. ↑ "NASA's large SLS rocket unlikely to fly before at least late 2021". 17 July 2019.
  46. ↑ "Casting Light on Permanently Shadowed Regions | Lunar Reconnaissance Orbiter Camera".
  47. ↑ "International Lunar Observatory to offer a new astrophysical perspective". 12 August 2017.
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