Permanently shadowed region of a body in the Solar System
The Moon'sErlanger crater is an example of a permanently shadowed crater.
Apermanently shadowed crater is a depression on a body in theSolar 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 onMercury[4] andCeres.[5]
A lunar south pole terrain in coded color. Several permanently shadowed craters are shown:Shackleton,Shoemaker,Cabeus
Such a crater must be located at highlatitude (close to apole) and be on a body with very smallaxial 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]
Craters of eternal darkness might be advantageous forspace exploration andcolonization, 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, includingRozhdestvenskiy[12] andCabeus craters[13] on the Moon, and Juling Crater on Ceres.[14] Other volatiles besides water can also be trapped in such craters, such asmercury.[15] TheLCROSS mission additionally found nativesilver andgold in permanently shadowed craters on the Moon, probably brought there by electrostatic dust transport, and some inconclusive evidence forplatinum. 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 ofhelium-3.[17]
The Moon's Shackleton Crater, as imaged by Earth-basedradar
Permanently shadowed regions have a stable surface temperature. On the Moon, the temperature hovers somewhere at or below 50 K (−223.2 °C; −369.7 °F).[18] Another temperatures estimate is 25 to 70 K (−248.2 to −203.2 °C; −414.7 to −333.7 °F).[19] The low temperatures make the regions desirable locations for future infrared telescopes.[20][11] For comparison: the boiling point of nitrogen at atmospheric pressure is 77.09 K (−196.06 °C; −320.91 °F).
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.[21][22] 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.[23]
In some cases,peaks of eternal light are located nearby, that could be advantageous for solar power generation. For example, there are two peaks nearShackleton Crater that are illuminated a combined ~94% of a lunar year.[24]
In 2020, NASA assigned "sensitive location" status to the Moon's permanently shadowed regions to avoid their contamination.[26] TheSETI Institute has a contract to manageplanetary protection measures for NASA.[27]
In 2009,LCROSS sent an impactor into a Cabeus crater, that resulted in detection of water in the ejected material.[13]
In 2012, The Lyman Alpha Mapping Project aboard NASA'sLunar Reconnaissance Orbiter has found that the permanently shadowed regions have a porous, powdery surface, that indicates the presence of water ice.[37]
In 2018, an analysis of the results of theMoon Mineralogy Mapper confirmed the existence of water ice deposits in permanently shadowed craters and crevices, with more abundance near the south pole.[10]
In 2022,Lunar Flashlight was launched as a secondary payload for theHakuto-R Mission 1 mission.[38][39] The cubesat mission failed to go into orbit around the moon when debris blocked propellant lines for the spacecraft’s thrusters.[40]
In 2025, theIM-2 lunar mission, conducted byIntuitive Machines forNASA'sCLPS program, landed aNova-C lunar lander.[41][42] The lander carried a hopper namedGrace,[43] a drone equipped with aneutron spectrometer to explore the permanently shadowed region of the nearby Marston crater.[44][45] The lander landed on its side and the hopper couldn't be deployed.[46]
A camera calledShadowCam has been built that is able to take high-resolution images of Permanently Shadowed Regions. It is a NASA instrument that flies on board theKorea Pathfinder Lunar Orbiter (KPLO) since 2022.[19]
^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.ISBN978-1-62410-315-5.
^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)
^abSanin, 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.S2CID130773165.
^"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 fromthe original on 30 November 2012. Retrieved20 July 2021.
.jpg)
This article incorporates text from this source, which is in thepublic domain.
