The far side of the moon has a certain mystique about it. The far side of the moon is always out of sight, and never faces Earth. This has given it the misleading name “the darkside”, as in sunlight doesn’t reach its surface . This is the part of the moon that we will never be able to see, unless we fly there on a spaceship.
But there are some parts that remain mysterious. They’re at the poles, where the sun always hovers near the horizon. The lighting conditions create special circumstances: Hundreds of craters at the north and south poles never, ever receive direct sunlight, and so never feel the warmth of our star. They are, in astronomy parlance, permanently shadowed regions, and they’ve been that way, dark and frigid, for as long as billions of years. While astronauts have seen the lunar surface from up-close, space probes have also mapped most of it. However, neither have ventured into the darkened craters below. With the right tools, astronomers hope, they’ll be able to peek inside and find something spectacular: water.
Not flowing water, of course–that’s not possible on the lunar surface–but ice crystals. Researchers believe water may have been present on the moon since ancient times, as it was delivered to it by comets or asteroids .. The same procedure is believed to have sprayed our planet water. The bombardment would have scattered icy particles across the surface, and particles that were exposed to the sun wouldn’t have lasted. But any bits of ice that might have tumbled into permanently shadowed regions would have been left untouched, sparkling in their freezing surroundings ever since. The environment is perfect; some sunless spots are colder than Pluto, says Prasun Mahanti, an Arizona State research scientist.
Scientists and engineers have probed permanently shadowed regions with several spacecraft missions over the years, Parvathy Prem, a planetary scientist at the Johns Hopkins Applied Physics Laboratory who studies the moon, told me. To determine if the hidden terrain is made from icy or rock material, they’ve bounced radar wave off the surface. They’ve done the same with lasers, to get a sense of the hidden topography. In 2009, a spacecraft fired a projectile into the moon’s south pole and then detected, in the resulting plume of excavated material, the distinct signature of H20.
But, no missions had ever targeted permanent shadowed areas with a photographer such as ShadowCam. This new NASA camera was launched in December aboard and is currently orbiting the Moon. . Mariah Heck is a Research Analyst Assistant at Arizona State University. She programs ShadowCam each day to record these secluded places. The ASU team plans to take photographs of every moon region that is permanently shaded in the future, and reveal their inner workings. The instrument has already provided a glimpse inside a crater near the moon’s south pole, which included a curious, previously unknown little furrow in the otherwise smooth soil–the path of a boulder that had rolled down the slope. This is the type of image that non-astronomers will immediately recognize. Prem stated that it was powerful to see shadowed areas at wavelengths our eyes can detect.
How do you illuminate a pitch-black hole on the moon? It’s not by hanging a flashlight from spacecraft, like I had originally imagined. Like other cameras that have documented the lunar surface, ShadowCam relies on sunlight reflected by landscape features, such as crater walls. “It’s like you’re standing in the shadow of a tree, but you can still see what’s on the ground because of all the light reflecting off of the stuff around you,” Heck told me. ShadowCam is more than 200 times more sensitive than its predecessors, which means it’s better at basking in dim, ambient light to reveal details cloaked in darkness. “We’re seeing the moon in a way no one’s ever seen the moon before,” they said.
Scientists weren’t expecting to spot signs of water ice in ShadowCam’s first photo shoot, which covered a region that isn’t cold enough to sustain it. But there are many places left to check. Prem said that Earth scientists have been conducting laboratory tests to find out how much lunar soil must contain water ice to make it visible from space. She said that “the quantities of ice we are likely to see at surface in visible lighting will be very small” but added, “If there is enough ice we should be capable of seeing it.” Other types of ice may also be detected by the camera, including nitrogen, ammonia and methane. It could even reveal there is no water ice. Although scientists are optimistic that this is not true, ShadowCam deputy principal investigator Mahanti said “that’s always possible.” “We really do not know what to expect.”
NASA is keen on getting close to permanently shadowed regions soon. The agency plans to dispatch to the south pole a new lunar rover next year, and a new generation of moonwalking astronauts later this decade, under the modern-day Artemis program, the successor to Apollo. Apollo’s astronauts were trained to land at locations along the sun-dappled moon’s equator. These sites proved easier and more safe for short missions. But the next generation of astronauts will arrive at the south pole. And if they can get their gloved hands on water ice, people could eventually return to the lunar surface with technology designed to extract its oxygen and hydrogen for use in life-support systems and even fuel, which would allow us to take up residence on the moon for weeks or months at a time.
The prospect of mining moon water is still closer to sci-fi than reality. ShadowCam and other missions will continue to explore the moon from afar. This adds texture to scientist’s daydreams of exploring its most mysterious shadows. Prem finds the idea of lighting them up at last almost transcendental. It’s as though we are trying to see something that was never meant to be lit. She said that there was something mysterious about a place that has been hidden from human sight for many billions of centuries.
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