shadowy craters and lighter highlands

In this multi-temporal illumination map of the lunar south pole, Shackleton crater (about 12 miles or 19 kilometers in diameter) is in the center, and the south pole is located approximately at 9 o'clock on its rim. The map was created from images from the camera aboard the Lunar Reconnaissance Orbiter. Full size image and caption. Image credit: NASA/GSFC/Arizona State University

NASA is working right now to send American astronauts to the surface of the Moon in five years, and the agency has its sights set on a place no humans have ever gone before: the lunar south pole.

Water is a critical resource for long-term exploration, and that’s one of the main reasons NASA will send astronauts to the Moon’s south pole by 2024. Water is a necessity for furthering human exploration because it could potentially be used for drinking, cooling equipment, breathing and making rocket fuel for missions farther into the solar system. The experience NASA gains on the Moon, including using lunar natural resources, will be used to help prepare the agency to send astronauts to Mars.

“We know the south pole region contains ice and may be rich in other resources based on our observations from orbit, but, otherwise, it’s a completely unexplored world,” said Steven Clarke, deputy associate administrator of the Science Mission Directorate at NASA Headquarters in Washington. “The south pole is far from the Apollo landing sites clustered around the equator, so it will offer us a new challenge and a new environment to explore as we build our capabilities to travel farther into space.”

The south pole is far from the Apollo landing sites clustered around the equator, so it will offer us a new challenge and a new environment to explore as we build our capabilities to travel farther into space.
- Steven Clarke

The south pole is also a good target for a future human landing because robotically, it’s the most thoroughly investigated region on the Moon.

The elliptical, polar orbit of NASA’s Lunar Reconnaissance Orbiter (LRO) is closest to the Moon during its pass over the south pole region. Through its thousands of orbits in the last decade, LRO has collected the most precise information about the south pole region than any other, offering scientists precise details about its topography, temperature and locations of likely frozen water.

“We’ve mapped every square meter, even areas of permanent shadow,” said Noah Petro, an LRO project scientist based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

There’s still so much to learn about Earth’s nearest neighbor. Ahead of a human return, NASA is planning many to send new science instruments and technology demonstration payloads to the Moon using commercial landers through Commercial Lunar Payload Services (CLPS). These robotic precursors will further investigate regions of interest to human explorers, including the south pole, and will provide information to the engineers designing modern lunar surface systems.

Water on the Moon

The floors of polar craters reach frigid temperatures because they’re permanently in shadow as a result of the low angle at which sunlight strikes the Moon’s surface in the polar regions (and also because the Moon has no atmosphere to help warm up its surface). This angle is based on the 1.54-degree tilt of the Moon’s axis (Earth’s is 23.5 degrees). If an astronaut was standing near the south pole, the Sun would always appear on the horizon, illuminating the surface sideways, and, thus, skimming primarily the rims of deep craters, and leaving their deep interiors in shadow.

These permanently shadowed craters feature some of the lowest temperatures in the solar system — down to -414 degrees Fahrenheit (-248 Celsius). Water ice is stable at these temperatures and it is believed that some of these craters harbor significant ice deposits.

Video: Permanent Shadows on the Moon

The south pole’s frozen water may date back billions of years and has been untainted by the Sun’s radiation or the geological processes that otherwise constantly churn and renew planetary surfaces (think of wind and erosion on Earth), offering us a window into the early solar system.

“That record of water collection is a record that can help us understand how water and other volatiles have been moving around the solar system, so we’re very interested in getting to these locations and sampling the material there,” said John W. Keller, a lunar scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Studying samples of ice from polar regions of Earth, for example, has revealed how our planet's climate and atmosphere have evolved over thousands of years.

Constant Light and Power

Other extremes at the Moon’s south pole are not so dark and cold ­— there are also areas, near Shackleton crater for instance, that are bathed in sunlight for extended periods of time, over 200 Earth days of constant illumination. This happens also because of the Moon’s tilt and is a phenomenon that we experience at our own polar regions on Earth. Unrelenting sunlight is a boon to Moon missions, allowing explorers to harvest sunlight in order to light up a lunar base and power its equipment.

The president’s direction from Space Policy Directive-1 galvanizes NASA’s return to the Moon and builds on progress on the Space Launch System rocket and Orion spacecraft, collaborations with U.S industry and international partners, and knowledge gained from current robotic assets at the Moon and Mars.

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