Kamal Ghorui
Scientists have intensely studied the Moon’s polar regions due to the ice found in Permanently Shadowed Regions. The newest study in Nature Astronomy confirms that the Moon has been accumulating ice for about 1.5 billion years. Researchers used data from NASA’s Lunar Reconnaissance Orbiter (LRO) to determine that the build-up of ice is a steady-state process of gradual accumulation from water delivered by comets and solar wind. As the axial tilt of the Moon has changed through time, these frigid traps for water have increased in size by capturing more water than when they were formed. This study shows that the polar regions of the Moon can provide a valuable resource for future missions to explore deep space more efficiently.
Moon quietly built up its water ice over 1.5 billion years
The key finding that this research provides is the correlation between the age of a cold trap and its water ice content. The Lyman-Alpha Mapping Project (LAMP) study suggests the Moon has had a decreasing angle of axial tilt (obliquity) since the formation of its cold traps (permanently shadowed regions) and that this orbital change has resulted in the various lunar polar craters being within permanent shadow at different times in the Moon’s history. Ice lying exposed on the lunar surface was discovered to be present in younger PSRs (formed approximately 100 million years ago) while older PSRs contained buried ice covered with regolith layers, as noted in the study, published in Nature Astronomy. This means that there has been a continuous, long-term accumulation and gardening of the lunar poles where water ice was added, covered, and preserved for 1.5 billion years.
How axial shifting created the Moon’s ‘cold traps’
While the accumulation of water ice occurs due to the Moon’s current position within a gravitational field, its ‘true polar wander’ has created conditions suitable for ice formation. The Moon’s mass and rotation act as a gravitational field upon the planet, changing as it spins, and with its changing mass distribution, this shifting of the Moon’s mass causes the Moon’s axial angle to change with respect to its orbital plane (ecliptic pole), which alters the amount of Permanently Shadowed Regions (PSRs) of the Moon. NASA’s Goddard Space Flight Centre states that PSRs are cold traps where water ice and water molecules remain stable for billions of years because of their extremely low temperatures below 110 Kelvin (-261 degrees Fahrenheit). As the Moon’s axial tilt changes and the number of regions of total darkness increases, the volume of water ice continues to increase in the PSRs by way of trapping processes.
Turning 1.5 billion-year-old ice into life support
Researchers have verified that there is a reservoir of ice approximately one and a half billion years old. This provides NASA with a new path for its Artemis exploration program. Rather than being in one large area, the ice is dispersed in different amounts with soil and various depths depending on how long ago it formed. Because of the uniqueness of this ice resource, it will take very careful and precise extraction methods. The ice is also an important ‘in-situ’ resource instead of only being used for scientific research. A way to utilise this ice is to electrolyse the water to produce hydrogen fuel and oxygen for rockets and oxygen to supply life-support systems for human missions. Therefore, ice on the surface of the Moon will become a critical strategic propellant reserve or ‘gas station’ for travelling to Mars.
