In the ongoing effort to prove whether the Earth's moon once held water and ice on its surface, scientists turned to decades-old data for additional clues, using photos taken during the Apollo Mission series. 

Researchers from the NASA Jet Propulsion Laboratory (JPL) in California turned to various moon landings from 1969 to 1972 in an attempt to solve the discrepancy between predictions made by computer models and those that were drawn from observations of the lunar surface.

The new analysis on the lunar surface is reported in the Monthly Notices of the Royal Astronomical Society, in the article "Implications of Surface Roughness in Models of Water Desorption on the Moon."

Terraced Wall Crater on the Lunar Limb
(Photo: NASA Apollo via Wikimedia Commons)
This oblique view featuring International Astronomical Union (IAU) Crater 302 on the Moon surface was photographed by the Apollo 10 astronauts in May of 1969. Note the terraced walls of the crater and central cone. Center point coordinates are located at 162 degrees, 2 minutes east longitude, and 10 degrees, 1 minute south latitude.

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Water in the Shadows of the Lunar Surface

Previous computer simulations tend to simplify the lunar surface, rendering it flat and almost featureless. These led to assumptions that water and ice could not have existed on the moon since it lacks natural barriers from sunlight, such as mountains, craters, ridges, and more. It would suggest that the surface of the moon receives uniform light and heat during its lunar daytime or when it faces the sun. This, in turn, would mean that water would dry up as soon as it faces the sun.

But why do lunar missions keep on reporting that traces of water are on the lunar surface?

A recent article from NASA JPL suggests that one possibility is that water molecules might find their way into rocks or even impact glass. These are hardened, crystallized surfaces made when a meteorite strikes on the lunar surface and releases immense heat upon impact. Once trapped inside these surfaces, water can stay without evaporating even when exposed to sunlight, creating the signals detected by ongoing studies such as that of SOFIA, and was reported by NASA in October.

However, JPL notes that one problem with the notion is that the same observations also showed that the amount of water decreases just before noon or when the sunlight on the surface is at its maximum. It suggests that instead of being actually trapped, water moves somewhere else across a lunar day.

The Importance of Shadows on the Moon

With the new study using the Apollo Mission images, led by scientist Björn Davidsson and research and instrument scientist Sona Hosseini, there might be new evidence to support that water and ice can be discovered at the moon's poles, particularly its permanently shadowed craters. These are the locations that do not receive sunlight after all.

In their new study, Davidsson and Hosseini suggest that the shadows cast by the roughness of the moon's irregular surface could provide refuge for water ice, keeping them and allowing them to form as frost over the lunar surface. 

The duo revised the computer model to start considering the roughness of the lunar surface, as evidenced by photographs from the different Apollo Mission images from 1969 to 1972. This results in a model that is filled with craters and boulders scattered around. It revealed several shadowed areas that could have offered natural protection from the sunlight.

Since the moon does not have an atmosphere that disperses heat across the entire object, temperatures can range from minus 350 degrees Fahrenheit (-210 degrees Celsius) in shaded areas to about 240 degrees Fahrenheit (120 degrees Celsius) in areas facing the sun.


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