China targets permanently shadowed regions at lunar south pole

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HELSINKI — China is looking to land spacecraft near permanently shadowed regions near the south pole of the moon to investigate the potential presence of resources trapped in craters.

Researchers from the Key Laboratory of Information Science of Electromagnetic Waves at Fudan University published a paper in the Journal of Deep Space Exploration on landing site selection in permanently shadowed regions (PSRs) on the moon, indicating that China’s Chang’e-7 mission will attempt a highly accurate, fixed point landing at a solar illuminated area, such as a crater rim near the lunar south pole.

The landing site will also be in the proximity of a PSR which could then be searched and sampled for detecting water and other volatiles. 

PSRs do not receive any sunlight due to their latitude and elevation. With temperatures around –230 degrees Celsius, PSRs are colder than the surface of Pluto, making them potential traps for volatiles including water ice but also methane, carbon dioxide, ammonia and more. 

Such resources could help support human explorers on the moon, with water ice converted into drinking water, or electrolyzed to produce rocket propellant.

The Chang’e-7 mission, expected to launch in 2024 or 2025, will consist of multiple spacecraft including an orbiter, relay satellite, lander, rover and “mini flying detector.” Searching for water ice in a permanently shadowed region (PSR) is noted as a major mission objective.

The PSR search will be carried out by the Chang’e-7 mini flying detector. A main candidate design appears to be a six-legged movable repetitive lander named HexaMRL and developed by Shanghai Jiao Tong University. The craft would be capable of numerous takeoffs and landings, moving using its six legs and sampling the lunar regolith.

The authors of the landing site paper use synthetic aperture radar (SAR) data acquired by the Mini-RF onboard NASA’s Lunar Reconnaissance Orbiter with optical images and utilize high-resolution digital elevation modeling to try to find flat areas within the craters Shackleton and Shoemaker for landing and regolith sampling by the mini flying detector. 

Insights from this process are then used to learn how the Polarization Synthetic Aperture Radar (Pol-SAR) to be carried by the Chang’e-7 orbiter can be used to evaluate the topography and roughness of the lunar surface to select landing and sampling sites.

The microwave imaging radar would enable high-resolution imaging of a shadowed region, where optical observations cannot be made.

The mission could have big implications for lunar exploration, if it confirms the presence of stored, accessible resources.

“PSRs are critically important because right now they contain the largest potential reservoirs of water and volatiles on the moon but we don’t know much about the reserve potential,” Clive Neal, a lunar scientist at the University of Notre Dame, told SpaceNews

“There have been a few studies using orbital data to try and estimate abundances within PSRs but we need 3D ground truth. So we need to get in and operate assets there to understand these PSRs and the ice that’s within them.”

“A “flying probe” or hopper is a way to get point data within a PSR and the data will be enlightening. But we need to get rovers in these PSRs to understand the real extent of the ice both at the surface and in the subsurface.” 

Neal notes that investigating PSRs will be challenging because of the temperature and navigation, but adds that data ShadowCam on South Korea’s upcoming KPLO mission will yield much needed navigational data for PSR exploration. 

Neal also notes that any volatiles in Shackleton may be kilometers distant from a landing site and down a 30 degree angle slope.

China is far from the only actor interested in lunar south pole volatiles. NASA plans to launch its Volatiles Investigating Polar Exploration Rover (VIPER) mission in late 2023, near the western edge of Nobile Crater.

Both China and the U.S. would place high value on areas containing volatiles, given both parties have long-term lunar plans, making their confirmation all the more important.

NASA is developing its Artemis Program which calls for a “sustained human presence” on the moon.

China has meanwhile announced plans to construct the International Lunar Research Station (ILRS) with Russia. While initially robotic, the station would be capable of hosting long-term human stays on the moon in the 2030s.