EXPLORING THE LUNAR POLES

The poles are of interest for both scientific and exploration reasons. The majority of impact craters near both poles contain permanently shadowed interiors that are extremely cold, < 110K, and can harbor ice deposits. The fact that the Moon’s spin axis is nearly perpendicular to the ecliptic plane also results in the existence of areas that receive near-constant sunlight. These represent excellent future exploration sites as they offer abundant solar energy, and also a relative benign thermal environment.

Perhaps more than anywhere else on the Moon, our knowledge of the lunar poles has increased the most in the last thirty years. Although the Moon was well mapped before and during Apollo, the vast majority of these data were acquired to support the manned landings, all of which took place in the equatorial region. The amount of polar data is limited to a handful of images acquired by the Lunar Orbiters IV& V.

Our first good look at the polar regions came from the Clementine mission. Clementine mapped the Moon for 71 days in 1994. During that time it took an image of each pole roughly every 10 hours. This permitted the production of the first quantitative illumination maps of the polar regions. These showed that nowhere near the south pole were permanently illuminated, and that areas near the north pole exist that are lit for an entire lunar day in summer. Additionally a bistatic experiment indicated the existence of ice in the permanently shadowed floor of Shackleton crater.

Later lunar missions, including ESA’s SMART-1, ISRO’s Chandrayaan-1 and JAXA’s Kaguya all added to our depth of knowledge of the polar regions.

Turning full circle from the 1960’s we currently have a mission in orbit around the Moon whose primary goal is to better understand the poles. NASA’s Lunar Reconnaissance Orbiter (LRO) has been orbiting the Moon since June 2009, using its payload of seven instruments to study the poles (and the rest of the Moon!) in unprecedented detail.