A new study has pieced together the first detailed map of water distribution on the Moon.
Scientists have mapped water near the Moon’s South Pole that could be vital for human bases.
The map was created using the now-retired Stratospheric Observatory for Infrared Astronomy (SOFIA).
As Nasa prepares to send astronauts back to the Moon under the Artemis lunar mission, the agency has identified thirteen potential landing zones near the lunar South Pole.
Through Artemis, Nasa will land the first woman and the first person of colour on the Moon, and lunar water could be a critical resource for establishing a long-term human presence.
‘Our common knowledge from the Apollo era that the Moon is bone dry was wrong,’ said Paul Lucey, a professor at the University of Hawaii at Mānoa and co-author on the paper. ‘We already know it’s wrong, but the question is by how much.’
With clear, identifiable lunar features marked out by the water data, the study provides hints about how water may be moving across the Moon’s surface, particularly near its South Pole – an important area for space exploration.
The new map covers about one-quarter of the Earth-facing side of the lunar surface below 60 degrees latitude and extends to the Moon’s South Pole.
Given the large area covered, the researchers could easily identify how water relates to surface features on the Moon, staying away from sunlight and favouring cold areas.
‘When looking at the water data, we can actually see crater rims, we see the individual mountains, and we can even see differences between the day and night sides of the mountains, thanks to the higher concentration of water in these places,’ said Bill Reach, director of the SOFIA Science Center at Nasa’s Ames Research Center in California’s Silicon Valley and lead author on the study, which was presented at the 2023 Lunar and Planetary Science Conference.
In late 2024, Nasa’s Volatiles Investigating Polar Exploration Rover (VIPER) will land in the region studied by SOFIA, atop Mons Mouton, a newly named lunar mountain, to conduct the first resource mapping mission beyond Earth.
This current finding, along with two previous SOFIA results about the amount and distribution of water on the Moon’s sunlit surface, tracks a unique light signature of water.
Other missions observing wide areas of the lunar surface have studied different wavelengths of light, which can’t distinguish water from similar molecules, such as hydroxyl. The Moon’s water is present in the soil and might be found as ice crystals, or as water molecules chemically bound to other materials.
Instead of determining the absolute quantity of water in the region, the researchers compared the data obtained around the Moon’s South Pole to a relatively dry reference region near the Moon’s equator to see how its abundance changes.
The water was found in greater concentrations on the shadowed sides of craters and mountains, similar to the way skiers on Earth know the slopes receiving less direct sun retain snow longer. This suggests the Moon’s local geography plays an important role in the amount of water present.
‘With this map of SOFIA data, and others to come, we are looking at how water is concentrated under different lunar environmental conditions,’ said Casey Honniball, a VIPER science team member at Nasa’s Goddard Space Flight Center, who was involved in the work.
‘This map will provide valuable information for the Artemis program on potential prospecting areas but also provides regional context for future science missions, like VIPER.’
In addition to the southern region for which the new map results were created, SOFIA observations of sites relevant to other missions are in the archive and now being analysed.
Nasa’s Artemis-related missions will target both polar and non-polar regions, including Lunar Trailblazer, which will orbit the Moon to map its hydroxyl and water.
Nasa is still trying to understand where the Moon’s water may be coming from. It could be ancient and exist inherently in the Moon’s minerals as a result of early volcanic activity or is contemporary and delivered by asteroids, comets, or solar wind.
However, Nasa is sure that even at its lowest limit, the Moon contains much more water than they once believed.
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