The lunar soil is apparently not as dry as expected.
According to researchers from the US space agency Nasa in the journal Nature Geoscience. Accordingly, small meteorite impacts regularly release water from the deeper soil layers of the Earth's satellite. The water probably comes from the time of the moon's formation, say the experts.
For their study, the scientists analyzed data from the probe "Lunar Atmosphere and Dust Environment Explorer" (LADEE). She had orbited the moon from October 2013 to April 2014. One of the objectives of the NASA mission was to study the atmosphere of the moon and the effects of dust particle impacts.
When analyzing the data, the researchers repeatedly found an abnormally high water concentration in the lunar atmosphere. In 29 cases, this deviation occurred shortly after the Earth's gravitational met with known meteorite currents. In addition, the scientists attribute four more anomalies to previously unknown meteorite currents.
However, the NASA experts quickly noticed that apparently only certain meteorites release water contained in the moon. The water concentration in the lunar exosphere was particularly increased when rocks with a mass of between 0.15 grams and 100 kilograms were smashed. From this, the researchers deduce that the upper eight centimeters of the lunar soil are completely dry. Only from a mass of 0.15 grams on impacting meteorites can expose deeper layers.
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Calculations showed that the water content of the lunar soil in more than eight centimeters deep is up to 0.05 percent. The researchers conclude that the lunar soil loses up to 200 tons of water per year due to meteorite impacts. In order to maintain this rate of loss over geological periods, the water must either have been present relatively evenly in the lunar soil from the beginning, or at least had arrived very early on the still young terrestrial satellite.
Water traces had been discovered on the moon ten years ago. Their origin is not clear yet. Among other things, the spacecraft "Cassini", "Deep Impact", "Lunar Prospector" and "Chandrayaan-1" had provided evidence of water release. The probe "Ladee" has now succeeded in observing this process, the researchers write. Earlier, other investigations had already encountered larger deposits of water ice in eternally sinister craters on the lunar poles.