Prime real estate

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The south pole of the moon

Since the 1990s, scientists have suspected that water-ice might be hidden in the forever-dark floors of the polar craters on the Moon. If so, these locations become valuable real estate, as they not only would provide future settlers water for drinking, the water itself can be processed to provide oxygen and fuel.

Moreover, the high points near these craters, including the crater rims, are hoped to be high enough so that the sun would never set or be blocked by other mountains as it made its circuit low along the horizon each day. If such a place existed, solar panels could be mounted there to generate electricity continuously, even during the long 14-day lunar night.

Below the fold is a six minute video, produced from images taken by Lunar Reconnaissance Orbiter (LRO) from February 6, 2010 to February 6, 2011, in an effort to find out if such a place actually exists. It shows how the sunlight hits the south pole across an entire year.

Before you watch, let me first give some explanation of what this video shows you. Each time LRO’s two-hour-long orbit took it over the south pole, it would snap an image, essentially a long swath with the sunlight coming from one end and the pole itself at the center. Because the Moon rotates below the spacecraft, the angle at which this swath was photographed changes each time. Thus, as you watch, the swath rotates around, completing one full rotation for each lunar day.

This means that the only place appearing in every image is the region around pole itself, and central to this region is the crater Shackleton, which NASA has made a considerable effort to study as it sits right on the south pole and appears to have a sufficiently useful flat area on its rim for establishing a lunar base.

As the swath rotates, Shackleton is always captured, and you can see the pattern of shadow and sunlight change on its rim from hour to hour. Unfortunately for future explorers, it appears from this compilation that there is no place on Shackleton’s rim that is illuminated continuously year round, though different parts of the rim get more light than others. A careful analysis of these images will tell engineers exactly what spot on the rim gets the most light, and even how high above the ground their solar panels would have to be mounted to remain forever in eternal sunlight.

In other words, this spot on the Moon is valuable because everyone is going to want to own it. Obviously, whoever gets there first will have the most say on that ownership.


One comment

  • James Fincannon

    A topic I know something about…

    While I agree that there is _likely_ no terrain which is illuminated 100% of the time at the lunar surface (either North or South pole) based solely on LOLA data, I have always had some problems with using imagery to deduce this.

    At the resolution of the imagery in the video, it is hard to see the spots that might be where solar arrays could get eternal light. This might be addressed if the full resolution images were examined although it is devilishly hard to register the images (i.e. get them to overlay precisely). But even if you could get the maximum resolution of the images and have them registered correctly, the resolution may still not be enough to see the eternal illumination (for solar arrays) spot. How small is acceptable?

    But it seems to me the most convincing imagery evidence of a spot of eternal illumination (for solar arrays) is a dark “spot” or location for about half the year (near the pole) around which is illuminated terrain. Why? Because the Sun’s rays during the worse time of year near the pole is either parallel to the surface or coming from below. So your flat lunar surface near the pole which may be the highest point around is going to be dark because the sunlight is passing parallel to the surface at best. Sure, the terrain adjacent and _around_ the “dark” spot/location may be getting illuminated, but during the lunar day (our month) as the Sun’s rays come from different directions, the surface around the “dark” spot will be getting less than 100% illumination. Finding such dark “spots” is hard because it’s hard to register the images correctly.

    But let’s say we don’t have to worry about the problems I mention above. Other problems include the regolith color. There is dark and light and average color regolith. If I am seeing a dark piece of surface, is it due to be regolith color being dark (absorbing all the light, not reflecting it)? These colors (or reflectivity properties) change based on Sun angle. Also, let’s say a spot was illuminated all the time, how can we tell that the Sun isn’t being partially blocked (>50% even)? For general illumination purposes, 50% Sun isn’t so bad (we can see using polarizing lens/shades/sunglasses), but for solar arrays it’s a different matter and would not count as fully lit. Also, since the orbit is 2 hours, we do not know what is going on illumination-wise when the camera is not imaging the spot. Sure, it is _only_ 2 hours, but some critical shadows from distant terrain could occur as the Sun is passing between mountain peaks/valleys.

    Regarding how high up you need to put a solar array for capturing the Sun 100% of the time, I did some analysis using LOLA showing the height was ~3500m (~3100m for south pole and ~1500m for north pole using terrestrial radar data of the Moon). You need to clear the shadows cast by Malapert Mountain.

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