Ice in the Lunar Polar regions (excerpt)
With the parade of anniversaries marking 50 years since the heights of the Apollo missions, humanity’s eyes are being drawn back to the Moon. At the time of this project, headlines are coming out daily marking progress politically and technologically towards returning to the lunar surface — yet we have been there before. Why has it taken so long for us to return? Why hasn’t our technological progress over the last half-century made lunar trips trivial? A host of reasons might be offered from social, political, and economic perspectives, but the foremost commonality amongst them is that traveling from Earth to the Moon was and remains a hugely challenging prospect. In order to have a successful and complete exploration of the Moon will require in depth analysis of the entire surface, including one of the more unexplored locales - the polar regions.
I am proposing a progression of missions in three phases to allow for human beings to exist safely on the lunar surface and work in conjunction with robotic elements to scientifically analyze and explore the shadowed regions of the lunar North pole. These sites are potentially an important resource for future lunar endeavors, as they might host an abundance of water ice. Ice is not usually considered a valuable commodity here on Earth when compared to other things people mine, like metals or precious stones. In space, however, the average person might have less need for shiny baubles than oxygen and rocket fuel — both of which can be created from H2O. Its proximity to Earth makes this solid water more easily utilized by humans, and the lower gravitational attraction on the surface of the Moon makes launches more efficient - having stores of hydrogen and oxygen in situ would be much cheaper than bringing these propellants from Earth. Even missions beyond the Moon (like Mars or beyond) would benefit tremendously from being able to “fill up” on the Moon’s surface or from orbit around it without having to blast off Earth already laden with these important reserves. So where do we find this icy motherlode?
The region of the moon identified as the focus of the mission is the polar region (80 degrees latitude to the poles themselves) due to the fact that the Moon’s spin access is nearly perpendicular to the ecliptic and these regions will therefore never receive direct sunlight to the degree that the equatorial regions do.
Graph 1: Elevation angle of Sun at 80°, 0° over one year (in yellow)
Graph 2: Elevation angle of Sun at 90°, 0° (lunar north pole) over one year (in yellow)Graphs 1 & 2 duplicated from Moontreks software.
The low apparent elevation of the Sun would be a bit like sunrise or sunset here on Earth - some taller or unshadowed features would receive sunlight (in fact some might be nearly constantly illuminated if tall or isolated enough) but others would be in constant shadow. Without an atmosphere or method of efficient heat transmission between these features, the warm spots stay warm and the nearby cold spots can be incredibly cold. (LPIpolesweb)
The presence of cold spots does not translate to the presence of ice though. For evidence of actual ice deposits in these regions we can look to evidence produced by the LCROSS impact - when the centaur stage of the mission struck the surface of the moon, the resulting ejecta was analyzed and found to have not insignificant concentrations of water within it. (Hayne et al. 2010) When the Lunar Reconnaissance Orbiter (LRO) mapped surface temp and brought these ideas together, the probability and observational evidence for water ice at the pole makes for an engaging possibility.
Image 1: Lunar north pole
Image 2: Lunar North pole
Mapped “temperature traps” for ice in white.
Image 3: detail of “Temperature Trap” (in white) distribution at LNP.
Images 1-3 duplicated from Moontreks software (NASA).
This abundance of water ice on the surface has been supported by polarization effects observed by NASA’s miniature Synthetic Aperture Radar instrument (Mini-SAR) on the Indian Chandrayaan-1 spacecraft (SARweb). While this is excellent supporting evidence, determining the chemical makeup, abundance, and distribution of the ice on the surface is challenging from a distance and surface level analysis could offer more certainty before extraction is attempted.
References (from complete paper)
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