Lunar Water - Evidence of Ice at the South Pole of the Moon

Lunar water may be more accessible than previously assumed, according to new Moon observations. The new information is especially interesting for NASA, which intends to use the Moon's resources particularly water ice embedded in the soil to aid future astronauts in living and working on the lunar surface.

Researchers discovered water directly on the lunar surface in one investigation, discovering the molecule on portions of the Moon that were lit by the Sun. According to a second study, water ice could be stored in tiny pockets or small craters strewn across the Moon's surface, making water possibly more abundant and accessible than we could have thought. Both studies were published in the journal Nature today.

It's not the first time that water has been discovered on the Moon. However, the only water we've been able to locate and verify thus far is quite difficult to access. It appears to be mostly found in perpetually shadowed huge craters at the lunar South Pole. The icy craters are extremely cold, possibly reaching -400℉, making contemporary technology nearly impossible to access. According to Paul Hayne, a planetary scientist at the University of Colorado and a primary author on one of the Nature papers, "these happen to be the coldest known regions in the Solar System, believe it or not."

Figure 1 Lunar Astronauts mining the rock samples on moon.

According to new studies published today, astronauts may be able to discover water in less dangerous parts of the Moon. "If we find that it's common enough in specific regions," Casey Honniball, a postdoctoral scholar at NASA's Goddard Space Flight Center and main author on one of the experiments, tells The Verge, "it would be easier to reach versus travelling into these extremely cold, very dark places."

Anyone interested in establishing a base or settlement on the Moon should consider extracting water ice from the Moon. Lunar water, if filtered, might be utilized as drinking water or to hydrate plants. Water can also be separated into its constituent elements hydrogen and oxygen and used as rocket fuel. Sending supplies to the Moon requires a lot of energy, time, and money, so if astronauts can use what's already there, it will cut down on shipments from Earth and help the astronauts stay alive.

However, what is true of liquid water isn't always true of solid water, such as ice. The problem with ice on the Moon is that the majority of its surface endures extreme temperature variations, ranging from extremely cold to extremely hot, depending on whether the Sun is shining or not. During the day, the average surface temperature is 107°C (with a maximum of 123°C) – much above the boiling point of water; at night, it drops to an average of -153°C (with a low of -233°C) over the entire Moon.

During a full lunar day, the Sun's rays illuminate the majority of the Moon's surface, rendering any ice on or near the surface impossible to survive. Many craters at or near the north and south lunar poles, on the other hand, have persistent shadows. Ice that had been deposited in such craters in the past may theoretically still is there now.

Possibility

To test this theory, numerous recent lunar orbiting spacecraft have been outfitted with instruments that can detect the presence of water ice on the Moon in a variety of ways. The Clementine mission, launched in 1994, provided the first evidence of ice near the Moon's poles. In March 1998, observations by Lunar Prospector1 provided confirmation, leading to an initial conservative estimate of 300 million tons of ice. Water-ice (or, more accurately, hydrogen) may be detected to a depth of 0.5 meter using the sensor aboard Lunar Prospector. Water might theoretically be present at this level since lunar soil has been changed over by meteorite impacts to a depth of around 2 m over the last few billion years. If this water is present as crystals in the lunar regolith, however, higher amounts of pure water ice deposits could exist at considerably deeper depths.

Figure 2 (a) Clementine Mission, uncontrolled image mosaic, detecting moon ice at the lunar south polar region- Orthographic projection. (b) The Lunar Prospector to detect traces of water ice at a concentration of less than 0.01 %.

In 2009, NASA's mini-SAR instrument, which was carried on India's Chandrayaan lunar orbiting mission, revealed additional data on lunar ice. A lightweight synthetic aperture radar called Mini-SAR discovered ice in more than 40 tiny craters. These craters range in size from 2 to 15 km (1 to 9 mi) in diameter. Although the total amount of ice in each crater varies depending on its thickness, it is estimated that at least 600 million metric tons of water ice exist.

Figure 3 India's moon mission, Chandrayaan-2, to detect the lunar ice and minerals at the south pole of the moon. 

Comets that impacted with the Moon in the distant past are assumed to be the source of the lunar ice. Although the majority of the water deposited on the lunar surface in this manner would have been evaporated long ago by the Sun's daily heat, it appears to have survived in small, permanently shadowed zones at the poles. Its presence demonstrates that water, whether frozen or not, is a common commodity on many worlds, which increases the chances of extraterrestrial life. Water is also abundant on the Moon, which is a major plus for any plans to establish a self-sustaining lunar colony.