THE LUNAR POLAR ENVIRONMENT: AN OVERVIEW

It has long been known that the lunar poles represent a unique environment on the Moon. Due to the spin axis of the Moon being near perpendicular to the ecliptic plane, areas of topographic lows and highs may experience illumination extremes. Specifically crater floors may be permanently shielded from the Sun whilst areas of high elevation may constantly see the Sun. Both of these extremes have value from a lunar exploration point of view.

Permanently shadowed regions are extremely cold, below 110 K and therefore represent cold traps for any water molecules that enter. Whilst the Moon has no indigenous water, molecules are brought to the Moon by cometary and asteroid impact. While most of the incoming water is lost back to space, a small fraction could be retained in these polar cold traps. Over the lifetime of the Moon a significant amount of ice could have been trapped. Evidence of possible ice deposits have been discovered by the Clementine bistatic experiment, and the neutron spectrometer on Lunar Prospector.

Areas of near-constant illumination represent ideal sites for extended surface operations. First is the abundance of solar energy, possibly continuous. Secondly is the relatively benign thermal environment. Whereas the temperature at an equatorial site varies by more than 250 K during a lunar day, it has been modeled that the temperature of a permanently illuminated are should be a constant 220 K.

We have conducted analysis of Clementine images, combined with modeling of polar topography to build up an understanding of the illumination conditions near the lunar poles. Key results include areas near the north pole that are constantly lit during the summer, and also the fact that permanently shadowed regions can exist many degrees away from the pole.