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Module 4 - Follow the Water

Lunar South Pole

LRO Diviner Lunar Radiometer Experiment surface temperature map of the south polar region of the moon. The data were acquired during September and October 2009 when south polar temperatures were close to their annual maximum values. The map shows the locations of several intensely cold impact craters that are potential cold traps for water ice as well as a range of other icy compounds commonly observed in comets. The approximate maximum temperatures at which these compounds would be frozen in place for more than a billion years is shown next to the scale on the right. The LCROSS spacecraft was targeted to impact one of the coldest of these craters, and many of these compounds were observed in the ejecta plume. Image credit: UCLA/NASA/Jet Propulsion Laboratory, Pasadena, Calif./Goddard

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Moon Even though our moon is not near Mercury, its surface conditions are similar to that planet. This means that the conditions for water on the moon are very similar to those for Mercury which is why we consider it next. The temperature range for the moon is between -233°C and 123°C for the dark and sunny sides respectively, the dark side does rotate towards the sun and it lacks an atmosphere.

The moon is tidal locked to the Earth which means that we always view the same, familiar side. The video on the side has a nice 2 minute explanation of why this came about. So we always see the near side of the moon, never the far side, which is shown in the image at the top of the page. Because the Earth and the moon orbit around the Sun all sides of the moon are eventually exposed to sunlight. The only locations that are permanently dark are once again craters near the lunar poles. Totally irrelevant side issue: So, by exchanging Far for Dark, this 1973 album would have been both, awesome and scientifically correct.

Back to science. We have long considered the possibility of lunar bases, both in reality and in a wide range of fiction. As humans we depend on a good supply of water so having a good supply of water available is absolutely crucial. As this NASA press release states:
A bottle of one of the most expensive brands of water costs $40 and is presented in a frosted glass container decorated with crystal. On the moon, a bottle of water would run about $50,000 and forget about that heavy crystal glass. That is because it costs around $50,000 per pound to launch anything to the moon. Discovering water on the moon would be like finding a gold mine.

In fact, scientists have discovered evidence for water or hydrogen, a component of water, in special places on the moon. Since the moon is not tilted much from its rotation axis, the depths of certain craters in the lunar poles may not have seen the sun for billions of years. The long night over these areas, called Permanently Shaded Regions (PSRs), will have made them very cold and able to trap water molecules as ice or hydrogen.
And so, the search for water on the moon has a long history, going back to the original Apollo program. We will only mention the latest effort, the LCROSS mission because in some ways it was the most exciting and it did confirm the presence of water. The mission involved impacting the upper stage of the rocket that carried the space craft into the moon. The impact took place near the Southern Pole of the moon.

This short video summarizes the LCROSS hard landing and findings.

The actual spacecraft with the scientific instruments then flew through the plume of debris ejected by the rocket impact and measured the composition of the plume. Then it too impacted on the moon. The results were positive. In 2010, analysis of the data, published in the Journal of Science stated:
On 9 October 2009, a spent Centaur rocket struck the persistently shadowed region within the lunar south pole crater Cabeus, ejecting debris, dust, and vapor. This material was observed by a second “shepherding” spacecraft, which carried nine instruments, including cameras, spectrometers, and a radiometer. Near-infrared absorbance attributed to water vapor and ice and ultraviolet emissions attributable to hydroxyl radicals support the presence of water in the debris. The maximum total water vapor and water ice within the instrument field of view was 155 ± 12 kilograms. Given the estimated total excavated mass of regolith that reached sunlight, and hence was observable, the concentration of water ice in the regolith at the LCROSS impact site is estimated to be 5.6 ± 2.9% by mass. In addition to water, spectral bands of a number of other volatile compounds were observed, including light hydrocarbons, sulfur-bearing species, and carbon dioxide
So, if we set up colonies on the moon, PSRs are where we want to be, or at least, where we want to go and get our water. You may not have to wait for long before we get one step closer. This lunar ice drill design was just unveiled and is (tentatively) scheduled to be deployed in 2020.