Shackleton crater in never-before-seen detail
NASA/KARI/Arizona State University
We’ve got our best look yet into the areas on the moon that sunlight never reaches. These permanently shadowed regions lie inside craters and depressions near the moon’s poles, and because the spin axis of the moon is only tilted about 1.5 degrees, they stay dark and cold year-round.
There are more than 300 known permanently shadowed regions, or PSRs, on the moon, but the fact that they are always dark makes it extraordinarily difficult to observe what is going on inside them. That is the goal of NASA’s ShadowCam instrument, which orbits the moon aboard the Korea Pathfinder Lunar Orbiter, also called Danuri.
Danuri entered orbit around the moon on 16 December 2022, and now ShadowCam has sent back its first image. The picture shows a region about 2000 metres wide inside Shackleton crater, near the lunar south pole.
This first image didn’t reveal any surprises, but it demonstrated that the camera works just as well as the researchers were hoping, says Mark Robinson at Arizona State University, ShadowCam’s principal investigator. Near the top of the image is the trail worn by a boulder about five metres across as it rolled down the sloped wall of the crater.
ShadowCam is 200 times more sensitive than the camera that was previously used to observe PSRs, which circles the moon aboard NASA’s Lunar Reconnaissance Orbiter. That high sensitivity allows it to peer into these dark areas using only the small amount of sunlight that bounces off the surrounding landscape.
The portion of Shackleton crater in this image is warm compared with other PSRs, regularly rising above the -163°C temperature that is required to keep water ice stable on the lunar surface. But other, colder PSRs – and maybe even colder regions of the same crater – are thought to host ice or frost, which may be useful for future missions to the moon.
Over the course of the next year or so, ShadowCam is expected to observe all of the known PSRs, Robinson says. The hunt is on for moon ice, and if it lurks in the shadows, this camera should be able to spot it.
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