A study published in Nature Geoscience indicates that water in small quantities is present at an underground depth of less than 8 cm, and has been preserved there since the early history of the moon.
The small meteorites that constantly bomb the lunar surface “displace” some 200 tons of water into outer space, according to the authors of an article published in Nature Geoscience. In addition, the results indicated that water in small quantities is present at an underground depth of less than 8 cm, and has been preserved there since the early history of the moon.
In the 1960s, when the Moon was explored using automatic probes and manned expeditions, scientists were convinced that the natural satellite was an absolutely dry body and that all the water that could exist in it had evaporated long ago, according to the results of the study of soil samples brought by the Apollo missions and the Soviet stations of the Luna series.
However, in the 1990s, data were obtained that shook this vision. In particular, data from the Lunar Prospector probe indicated signs of the presence of large amounts of ice in shaded areas of the poles. Subsequently, these observations were confirmed by the LRO and LCROSS devices. Scientists believe that ice deposits in “cold traps” could have formed as a result of falling meteorites composed of hydrated minerals and cometary nuclei consisting mainly of ice. Upon impacting the lunar surface, the water molecules were released and “condensed” into cold traps, where they remained for billions of years.
Although the scientists managed to build models of the lunar water cycle (including the formation of water as a result of the “implantation” of the solar wind protons and the release of water as a result of the meteorite fall and its transport through the exosphere lunar), some questions remained elucidated.
For example, it was not clear if the main source of water came from the surface or from the meteoroids; if the impacts of the latter could maintain a constant concentration of water in the exosphere; and if they can be the main source of water in cold traps. On the one hand, the Lunar Prospector data indicated that the upper layer of the lunar soil contained 180 to 1350 ppm of H 2 O, which induced a possible solar origin, but the Indian Chandrayan-1 device did not detect water in those same areas.
Water and rock pumps
Now, a group of scientists led by Mehdi Benna of NASA’s Goddard Space Center decided to answer this question by analyzing the information compiled by the LADEE lunar orbital probe ( Lunar Atmosphere and Dust Environment Explorer). During the eight-month mission, the device investigated the composition of the lunar exosphere using an NMS spectrometer; managed to collect data on the amount of key volatile substances, including methane, helium, neon, argon, among others. In addition, the probe produced 743 measurements of the number of water molecules and OH hydroxyl groups.
The average value detected was 22.8 molecules per cm³. However, the scientists found 214 cases of an acute excess of H2O over the “bottom”: more than 10 times. In addition, these anomalies occurred mainly between mid-November 2013 and mid-January 2014, corresponding to the period of peak activity of the famous meteor showers (Leonidas, Geminids and Quadrantids) that bombard both the Moon and the Earth.
In this way, the calculations indicated that most of the water was “generated” by meteoroids that hit the lunar surface with sufficiency in its crust, releasing the entrapped water. It is estimated that at a depth of less than 8 cm, the water concentration ranges from 220 to 520 ppm; and in a year, the meteorites would have released 300 metric tons of water, of which 200 went into space.
This new research supports previous studies that affirmed widespread and relatively immobile water dispersion in Earth’s natural satellite. Also, scientists reported that the Moon would have been transiently habitable 4,000 million years ago when water was an active and essential component to allow the presence of life as we know it.