Water Ice on the Moon: A Lunar South Pole Observing Challenge

Water ice on the Moon! Only a few years ago we recognized the 50th anniversary of Apollo. Now returning human astronauts to the moon has never been more compelling, especially with the increasing evidence for water ice deep within the south pole craters of the moon. The excitement is increasing as NASA’s Artemis mission approaches its goals to return humans to the moon and set the stage for Mars with a moon base near the south pole, where water has been detected instrumentally by NASA’s orbiting probes. The necessary proof, of course, will be for astronauts to actually locate and recover samples of water ice. A few of the south-most lunar craters are named after earth’s Antarctic adventurers from a century ago: Amundsen, Scott, and Shackleton. The moon’s rotation axis passes through Shackleton a few km from its center. Observing the polar craters edge-on with a telescope is a real challenge and requires a favorable libration in which the moon’s tilt reveals more of the south pole area. For an excellent high resolution imaging video of the south pole region and Shackleton crater, see this article from NASA and the Planetary Society. https://www.planetary.org/articles/water-on-the-moon-guide. At the most favorable southern libration over a few nights each month an earth observer can see about 6 degrees beyond the pole. Sky & Telescope lists the favorable libration dates for north and south poles on the almanac page (center-fold star map) each month. For more ideas on when and how to observe the south pole craters, see Sky & Telescope, March 2022, “Meet Shackleton Crater: Future Moon Landing Site”. Here I’m proposing a AAAP observing challenge to see how close to the south pole you can observe, image, and identify craters through a telescope at high magnification. If you do succeed in getting an image that shows the near-south-pole craters, please send it in to Sidereal Times and we will talk about it at an upcoming meeting. The deeper craters near the moon’s poles remain in permanent shadow and are extremely cold, below -200 deg C, where water ice is stable even in the vacuum of space. Deep shade turns out to be the key to whether abundant free water ice exists on the moon, and the answer means everything to future human habitation. Moon atlases as recently as the mid-90’s, such as my edition of “Astronomy Atlas of the Moon” (1996) by Antonin Rukl, states “there is no water on the moon – not even in the rocks”. The first evidence for free water ice came from NASA’s Clementine and Lunar Prospector missions in the late 1990’s, and the instrumental data from more recent missions is convincing. Imagine an astronaut actually holding ice crystals, and someday even drinking water from the deep polar craters of the moon. Let’s hope that this happens in the next few years with Artemis, and that the Shackleton crater scenes in the acclaimed science fiction drama TV series, “For All Mankind”, do come true.