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The frozen side of the moon

A new study by Weizmann Institute of Science scientists and their research partners in the USA indicates that at least some of the water on the moon may be trapped in much more accessible places - in pits and small depressions

The scarred surface near the North Pole of the Moon as captured by one of the cameras of NASA's LRO probe. The first step of the researchers was to decipher the two-dimensional images in an attempt to understand how many pits and depressions there are in these areas, what their possible depth is and what proportion of their surface is permanently shaded NASA /GSFC/ASU
The scarred surface near the North Pole of the Moon as captured by one of the cameras of NASA's LRO probe. The researchers' first step was to decipher the two-dimensional images in an attempt to understand how many pits and depressions there are in these areas, what their possible depth is and what proportion of their surface is permanently shaded NASA/GSFC/ASU

If and when humans settle on the moon, it is likely that they will choose to settle in the areas near the poles, since that is where the few water reserves of this arid patch of sky are found. Even in such a scenario, access to water is not expected to be easy at all - so far these reservoirs of frozen water have been discovered in places where access is particularly difficult: in the dark bottoms of gigantic craters where temperatures do not exceed minus 160 degrees Celsius even on the hottest day of the year. However, there may also be good news for those future settlers: MNew research of the scientists of the Weizmann Institute of Science and their research partners in the USA indicates that at least some of the water on the moon may be trapped in much more accessible places - in pits and small depressions. 

The absence of an atmosphere and the high temperatures that prevail during the day do not allow water to form on the surface of the moon, but due to its slight inclination on its axis, the giant craters in the areas near the poles are always in shadow, and therefore can store ice. Since the idea was first raised in 1961, many space missions of various countries have provided evidence of the existence of these ice reservoirs. Prof. Oded Aharonson From the Department of Earth and Planetary Sciences at the Institute and its research partners - Prof. Paul Hein from the University of Colorado in Boulder; Dr. Norbert Schraghofer of the Honolulu Planetary Science Institute speculated that smaller pits and depressions formed in these areas may also be cold enough to trap and store ice.

Data from the LRO probe

To investigate the matter, the team of researchers used data obtained from the instruments on board NASA's LRO probe, which has been mapping the moon in high resolution for more than a decade. One of the probe's cameras, the narrow angle camera - connected to a powerful telescope - provided them with close-up images of the moon's surface scarred at both poles. The first step was to decipher the two-dimensional images in order to understand how many potholes and depressions are in these areas, what their possible depth is and what proportion of their surface is permanently shaded.

But are these dark holes cold enough to trap ice? Another instrument on the probe provided scientists with information about average temperatures in the region, but could not reveal the specific temperatures at the bottom of the depressions. To this end, the researchers calculated the degree of possible influence of various heat factors in the vicinity of the depressions - for example, a protruding rock or light reflections - on the bottom temperatures. The results of their calculations indicate that even depressions less than a meter in size may constitute "cold micro-traps" with small amounts of frozen water. "According to our models, this is indeed only a small part of all the ice on the moon, but instead of going down to the depths of deep and unfriendly craters, future visitors to the moon - whether as part of a scientific mission or as part of a colonization mission - will be able to 'pump' water from small ice reservoirs And more are available," says Prof. Aaronson.

The researchers also examined the distribution and density of the ice traps - both small and large - at both poles, and they estimate that their area reaches about 40,000 square kilometers - more than double compared to previous estimates. About 60% of these surfaces are in the South Pole, although a higher proportion of small depressions and craters is found in the North Pole.

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