The south pole of the Moon is the newest hot spot in space for robotic and upcoming human missions. This region is home to some harsh conditions, including temperatures as low as -233 Celsius (-388 Fahrenheit). The area is heavily cratered, and the sun barely grazes the horizon, scarcely illuminating the surface at these latitudes. Shadows in some craters never fade, leaving icy walls and floors in eternal darkness.
Those conditions, which seem to make an inhospitable place even less inviting, is part of what makes this region so appealing.
Water ice, eternally frozen in eternal darkness deep within craters there, could be harvested, providing travelers to the Moon with water, air, and rocket fuel. Now, a new study shows harvesting water ice from within these craters could be easier than engineers expected.
“People think of some areas in these polar craters as trapping water and that’s it. But there are solar wind particles and meteoroids hitting the surface, and they can drive reactions that typically occur at warmer surface temperatures,” stated William Farrell, a plasma physicist at NASA’s Goddard Space Flight Center, who led the lunar frost research.
The Moon Convoy
NASA has their sights set on the south pole of the Moon for their next crewed mission to our planetary companion. Artemis 3, due for launch in 2024, is scheduled to bring the next human crew to the lunar surface, including the first woman to walk on the Moon. But, this mission is not the only one headed to our planetary companion.
China is focusing intently on exploring the Moon, and the Chinese National Space Agency (CNSA) has announced plans to build a Moon station in the next 10 years. In January 2019, the Chinese Chang’E 4 lander and Yutu-2 rover became the first vehicles to ever safely touch down on the far side of the Moon. The Chinese space agency, CNSA, is on-schedule to carry out a series of launches to the southern regions of the Moon over the coming years.
India, the world’s second-most-populated nation, is experiencing a boon of research as they join the United States, Russia, and China on the surface of the Moon. On July 22, 2019, India launched the Chandrayaan-2 orbiter, along with the Vikram lander and Pragyan rover, to the southern regions of our planetary companion. Multiple science experiments aboard that trio of spacecraft will scour out and map deposits of water for further exploration.
Is that an Oasis?
“High and fine literature is wine, and mine is only water; but everybody likes water.”
― Mark Twain
The Moon was once thought to be a dead, airless, dry world, offering little assistance to those who will, one day, colonize space. The detection of water on the Moon by several spacecraft show the heavily-cratered south pole could provide the first oasis on our way through the frigid desert of space. Water ice has also been detected at the north pole of the Moon, although most deposits are found in the southern polar region.
Water was deposited on the Moon as comets hit the surface, and water may be produced on the lunar surface through chemical reactions triggered by the Sun. Water molecules may even migrate around the Moon, although only over short distances.
When researchers examine the regolith, or lunar soil, they expected to find solid ice. Instead, what they found was wispy frost of ice dispersed throughout the sample. Impacts on the lunar surface by micro-meteorites could explain this unexpected finding, researchers suggest.
“Spacecraft orbiting the Moon have detect a low density water frost on the floor of some of the south polar craters ‐ regions that are known to be very cold and can trap water & other volatiles. The floor of these craters are also exposed to the space environment including incoming meteors and ionized gases from the sun,” researchers described in an article published in the journal Geophysical Research Letters.
Unlike the Earth, the extremely thin atmosphere of the Moon does not protect our natural satellite from the solar wind or impacts from small asteroids. These conditions are slowly driving water off from an extremely thin layer of the lunar crust. Bits of debris thinner than a human hair kicked up in these mini-collisions can fly nearly 32 kilometers (20 miles) from the impact in the largely air-free, low gravity environment before landing.
“So every time you have one of these impacts, a very thin layer of ice grains is spread across the surface, exposed to the heat of the Sun and to the space environment, and eventually sublimated or lost to other environmental processes,” said Dana Hurley, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory.
One intriguing idea is the possibility of a water cycle on the Moon. Water is deposited on the surface by comets, or forms from solar wind, and is transported to other places by the impact of micrometeorites and chemical processes before collecting and dispersing once more.
Don’t Forget Your Galoshes!
One of the problems with spaceflight, whether robotic or human, is that a spacecraft needs to carry everything needed for the flight, including fuel, and life support for human missions. These necessities add significant weight to the rocket, and cost to the flight.
A ready-made storehouse of water on the Moon (and the air and fuel which can be produced from it), will mean space travelers will not need to bring as much air, water, or fuel on their journeys, This would greatly ease the challenges of travel within the inner Solar System. If travelers to the Moon can obtain water from ice (through mining or by natural processes), colonizing the lunar surface becomes slightly easier, and much less expensive, than having to carry water from Earth.
“This research is telling us that meteoroids are doing some of the work for us and transporting material from the coldest places to some of the boundary regions where astronauts can access it with a solar-powered rover,” Hurley stated.
It would, naturally, be foolhardy to embark on a journey to another world without water, air, and fuel unless one were certain these supplies could be procured along the way. Robotic explorers from the United States, Europe, China, and India are exploring the lunar south pole for that vital ingredient of life — water.
The Lunar Reconnaissance Orbiter (LRO), launched in 2009, detects hydrogen, the main ingredient in water, in order to find hidden reservoirs of ice. Light has not fallen in some of the darkest craters for billions of years.
The Lyman Alpha Mapping Project (LAMP) instrument aboard the LRO provides evidence frost seen at the lunar poles is just 2,000 years old. This would suggest a significant means of replenishing water is taking place on the lunar surface.
As NASA pieces their own crewed mission to the Moon, China and India are both focusing their sights on the robotic exploration of the Moon. Private space entrepreneur Elon Musk recently told Time Magazine that his company, SpaceX, could land a robot on the Moon in two years, and place a person on the lunar surface in just four years.
Everyone has their eyes set on the newest, most desirable territory in the planetary neighborhood — the south pole of the Moon.
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