By Carmen Rodriguez / Madrid / The Moon has frozen water on its surface, according to unmistakable detection data, and there are numerous craters, including very small ones, where sunlight never enters and where it could be possible for this ice to remain trapped in a stable state, a find that could have significant implications for future manned missions to the Earth’s satellite.
Nature Astronomy on Monday published two studies carried out by US scientists, one of which discusses the unequivocal detection of molecular water – that is, H20 – on the Moon and the other suggesting and approximately 40,000 square meters (some 430,000 square feet) of the lunar surface, of which 40 percent are in its southern hemisphere, are able to retain water in so-called cold traps.
Two years ago, scientists had detected signs of moisture on the lunar surface, particularly around the South Pole, which possibly corresponded to the presence of water, but the method used could not distinguish between whether it was molecular water or hydroxyl radicals – the chemical symbol for which is “OH.”
In this new study, the team led by Casey Honniball of the University of Hawaii, used data from NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA), a Boeing 747SP jet modified to carry a reflecting telescope.
The data was collected from the huge Clavius crater near the Moon’s South Pole, which was observed with SOFIA at a wavelength of six microns, where molecular water produces a unique spectrum signature.
Earlier observations, at a wavelength of three microns, showed indications of water that still left open an alternative explanation,” but the new data eliminate all other explanations than that they definitely emanate from molecular water, Ignasi Ribas, an astrophysicist with the Space Studies Institute of Catalonia (IEEC) and the CSIC Space Sciences Institute, told EFE.
The water molecules, trapped inside grains of dust or crystals, vibrate when excited by sunlight and emit radiation at the six micron wavelength.
“In practice, it’s as if those parts of the Moon shine more than what they should at that wavelength,” said Ribas in commenting on the article, which he had no hand in preparing.
Researchers estimate that the abundance of water in the high southern latitudes is between 100-400 grams of H20 per ton of regolith (or lunar surface) and the water is distributed in that small latitude range due to local geology and “probably” is not a global phenomenon.
The amount of water on the Moon is much less than is present on Earth, “but it’s more than zero,” said Ribas, who noted that the conditions on the Moon are extreme because it is difficult to retain it there on the airless surface since it evaporates easily and escapes into space.
The second study, headed by Paul Hayne with the University of Colorado Boulder, examined the distribution of water on the lunar surface in areas that remain in eternal shadow, where the ice could be captured and remain stable.
In the cold traps, temperatures are so low that the ice behaves like stone, and if water gets into those areas it will not go anywhere else for billions of years,” the scientist said.
Although it cannot be tested from Earth whether the cold traps really contain reserves of ice – the only way to do so being to go there in person or with rovers and dig, said Hayne – the results are “promising” and future lunar missions could shed more light on whether water resources exist on the Moon.
The study was carried out with data from NASA’s Lunar Reconnaissance Orbiter to evaluate a range of possible cold traps, which could be much more common on the lunar surface than earlier investigations had suggested.
The team also used mathematical tools to recreate how the lunar surface might look at very small scales and the result is that it could look like a “golf ball” with countless small holes and cavities in it where ice could collect.
The study indicates that these “micro” cold traps, sometimes no larger than a dime, are hundreds or thousands of times more numerous than larger ones and could be found near both lunar poles.
The authors suggest that some 40,000 square meters of the lunar surface could be able to trap water.
If scientists are on the right track, Hayne said, water could be more accessible than previously thought and this would have crucial implications for the establishment of manned lunar bases.
Nevertheless, it is still not known how available this water ice is or whether it could be used as a resource by crewed Moon missions.
NASA is planning to send a crewed mission to the Moon in 2024 and to establish a permanent human presence there by 2030 as a springboard for a future Mars mission. (October 26, 2020, EFE/PracticaEspañol)
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