There’s more water on the Moon than expected, even in sunlit areas

The Moon, water, and the SOFIA flying telescope
Two articles – available here and here – published in the journal “Nature Astronomy” report as many studies on the presence of water on the Moon. A team of researchers used the SOFIA flying telescope to find direct evidence of the presence of water molecules even in regions other than the polar ones. Another team examined the so-called cold traps, regions in the shadows on the lunar surface where there’s perennial darkness that can allow the presence of water ice, mapping their distribution. In the end, the amount of water present on the Moon may be far greater than that known from previous research. However, there are still various questions, starting with the possibility that it’s partly present in glass beads and therefore not immediately usable in space missions.

In little more than a decade, the study of the Moon by various space agencies conducted by space probes in orbit has revolutionized our ideas regarding the presence of water on the site. From a total lack of evidence of its presence, we passed in a few years to various detections of its presence. To these were added the results of in-depth examinations of lunar rocks brought to Earth in the Apollo 15 and 17 missions with the discovery that they contain traces of water inside some glass beads.

These discoveries have increased the interest in the search for water on the Moon and the SOFIA (Stratospheric Observatory for Infrared Astronomy) flying telescope was used for this purpose too. The results were positive and SOFIA’s FORCAST (Faint Object infraRed CAmera for the SOFIA Telescope) spectrograph detected traces of water in Clavius ​Crater. The surprise came from the fact that it’s not a polar area or a cold trap but an area hit by sunlight.

The image (NASA/Daniel Rutter) shows the Moon with the Clavius ​​crater indicated and pointing to the detail of the rock containing water molecules. Below, the Boeing 747SP carrying the SOFIA flying telescope.

Alessandra Roy of the SOFIA project at DLR, the German space agency, explained that the temperature in the lunar areas illuminated by the Sun can reach 230° Celsius, so we need to understand how it can not evaporate and disperse in space. There are two theories of which one is supported by various discoveries in other areas because it’s the one about glass beads of meteoric origin while the other concerns a possible formation of water in two stages with a hydroxyl group formed by a hydrogen atom bonded to an oxygen one that binds to the hydrogen carried by solar wind.

The water discovered has a very low concentration, estimated at one hundredth of that present in the Sahara desert. If it were actually imprisoned in glass beads, the problem of its extraction would also arise.

Probably in the cold traps studied in the other research, water is simply in the form of ice that can remain solid thanks to perennial shadow conditions existing in certain craters. An examination of the areas where those traps might exist suggests that they could exist in amounts significantly greater than previous estimates for an ice surface twice as large as previously estimated.

Paul Hayne of the University of Colorado, first author of this research, explained that that ice could be an accessible source of drinking water, rocket fuel and for other needs related to human missions to the Moon. Easily usable ice reserves could be an important key to lunar bases.

In fact, it’s not currently provable that all the various cold traps contain ice reserves, but the results are promising. Future missions could conduct on-site examinations to obtain a mapping of the water actually available to understand which are the areas where local resources are best to support crewed missions and even Moon bases.

These discoveries are not revolutionary because some previous ones had already revealed the presence of water in various areas, for example in a research published in July 2017. However, its presence is greater than previously estimated, even if follow-up detections will be necessary to obtain real measurements of its amount. Surely the continuous discoveries and new projects of Moon missions, including crewed ones, will stimulate more search for lunar water and projects to extract it.

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