Shadow Games: Exposing a Hidden World on the Moon

Shadow Games: Exposing a Hidden World on the Moon

Look inside a dark crater


David Kring of the Universities Space Research Association at the Lunar and Planetary Institute was co-author of the article “Cryogeomorphic characterization of shadow regions in the Artemis exploration zone” published in Geophysical Research Letters.

Imagine a world where the Sun never passes overhead and instead always moves in a circle along the horizon, casting long shadows that spin across the landscape. This world is the lunar south polar region, which will soon be explored by the astronauts of Artemis.

Because the Sun hovers near the horizon, the sunken floors of impact craters in the region never see sunlight and are in perpetual shadow. These permanently shaded regions are incredibly cold, below 100 K (or below -280°F) and close to absolute zero. At these temperatures, water vapor and other volatile substances can be frozen in the lunar soils, even if these soils are exposed to the vacuum of space.

The potential for ice makes these shadowy crater floors intriguing sites to explore. The ice may hold clues to the routing and processing of water to the Earth-Moon system. Ice can also provide resources for astronauts to use for consumption, radiation shielding, and rocket propellant.

But designing exploration plans in such regions is difficult. What is hidden in these shady regions? Where within them will our astronauts venture?

This puzzling problem was recently solved by an international team of scientists who developed a method to see into these dark regions of the Moon. Their work is published in the current issue of Geophysical Research Letters. The article is led by Valentin Bickel, a former graduate intern at the Lunar and Planetary Institute (LPI) in Houston, and now a postdoctoral researcher at ETH Zurich, Switzerland. Dr. Bickel’s former LPI mentor, Dr. David Kring, principal investigator of the Center for Lunar Science and Exploration at LPI-NASA Johnson Space Center (JSC), co-authored the study with Dr. B. Moseley (University of Oxford, Oxford, UK), Dr. E. Hauber (German Aerospace Center, Berlin, Germany), Dr. M. Shirley (NASA Ames Research Center, Mountain View, California) and Dr. J. -P. Williams (University of California, Los Angeles).

Areas that were once dark are made visible using a physics-based, deep learning-based post-processing tool to produce images from the Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC) at high signal and high resolution that effectively capture bounced photons in shadow. regions of adjacent mountains and crater walls. This allows the team of scientists to provide the world with images of potential exploration regions. As LPI’s Dr. Kring explains, “Visible routes in permanently shaded regions can now be designed, greatly reducing the risks to Artemis astronauts and robotic explorers.” The spacesuit being developed for the Artemis astronauts will allow them to spend at least two hours in these shaded grounds. Using the new images, mission planners can direct astronauts to rocks to sample in shaded areas and places where trenches can be dug in the ground to assess the distribution of any ice.

The authors applied their new technique to images collected by the Lunar Reconnaissance Orbiter Camera, which has been documenting the Artemis exploration area for more than a decade. The team used these enhanced images to determine that water ice is not visible in the leaves covering these shaded areas. Dr Bickel says: “There is no evidence of pure surface ice in the shadowed areas, implying that any ice must be mixed with lunar soil or below the surface.” Dr. Bickel also notes that this work has an immediate impact on NASA’s PRIME-1 payload delivery mission: “We are detecting an approximately 50-meter-wide crater and other surface features in an area which could change the location where the hopper lander, Micro-Nova, could land next year.

The findings published in the new paper are part of an in-depth investigation of potential Artemis landing sites and lunar surface exploration options conducted by the LPI-JSC Center for Lunar Science and Exploration. So far, the team has reviewed more than half a dozen potential landing sites for Artemis astronauts and complementary robotic missions.

Dr. Kring’s work was supported by NASA’s Solar System Exploration Research Virtual Institute (SSERVI).

About the USRA
Founded in 1969 under the auspices of the National Academy of Sciences at the request of the United States government, the Universities Space Research Association (USRA) is a nonprofit corporation dedicated to advancing science, technology, and engineering related to space. The USRA operates scientific institutes and facilities and conducts other major research and educational programs. USRA engages the academic community and employs in-house scientific leadership, innovative research and development, and project management expertise. More information about the USRA is available at

About LPI
The Lunar and Planetary Institute (LPI), operated by the Space Research Association of Universities, was established during the Apollo program in 1968 to foster international collaboration and serve as a repository for information gathered during the early years of the program spatial. Today, LPI is an intellectual leader in lunar and planetary science. The Institute serves as a scientific forum attracting world-class visiting scientists, postdoctoral fellows, students and resident experts; supports and serves the research community through newsletters, meetings, and other activities; collects and disseminates planetary data while facilitating community access to NASA science, and engages, excites and educates the public about space science and invests in the development of future generations of explorers. Research conducted at LPI supports NASA’s efforts to explore the solar system. More information about LPI is available at

PR contact:
Suraiya Farukhi, Ph.D.
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Technical contacts:
Dr. David Kring
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