The surface of the moon can change not only as a result of its "bombardment" by meteorites, but also due to lightning strikes, signs of the existence of which were found by the LRO probe in the coldest and darkest craters, according to an article published in the journal Icarus.
The surface of the Moon is covered with large craters, most of which were formed in the distant past, about 3.8 billion years ago, at a time when the Earth and its companion were "bombarded" by large asteroids. Some of them began to attract the attention of scientists especially strongly after the Indian Chandrayan probe and the Russian LEND instrument aboard the American MRO probe found ice in the darkest craters on the Moon.
Andrew Jordan of NASA Ames Research Center in Moffett Field (USA) and his colleagues wondered what else these particles of the "dark moon" could hide in themselves, studying the strange data received by the CRaTER instrument aboard the probe LRO.
This device, the scientists explain, is designed to study how much cosmic rays and charged particles from the solar wind fall on the lunar surface, and estimate how much radiation will be received by astronauts that NASA plans to send to the moon at the turn of 2020.
Studying the data collected by CRaTER, Jordan and his colleagues noticed unusual bursts in the number of solar wind particles that occurred during the flight over the craters, where eternal darkness reigns and where, as observations with LEND show, significant reserves of water are hidden. The accumulation of charged particles in the soils of these craters, as well as the unusually high soil temperature in them, made scientists think about what consequences it could lead to.
As the researchers explain, regolith - the soil of the Moon - practically does not conduct current, due to which the charged particles of the solar wind, falling on it, will not lose their charge and discharge. Over time, the strength of the electric field generated by these particles will gradually increase, which under certain conditions - for example, in the presence of an electrically conductive medium - can lead to the formation of lightning and powerful electrical discharges.
Most corners of the moon do not have such an environment, however, as Jordan's calculations show, it can arise inside dark craters with significant water reserves. In this case, the conductor of electrical discharges will be water vapor formed inside the soil. Traces of their existence should be clouds of steam, thrown out after a lightning discharge into open space.
If these lunar lightnings really exist, then they will have an extremely unusual character. First, they will be born not above the soil surface, but inside it, at a depth of a millimeter from the surface. Secondly, their birth will lead to significant geological changes - the discharges of electricity will intensively evaporate the regolith and stir its grains.
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According to Jordan and his colleagues, lunar lightning should play no less a role in changing the appearance of the Earth's companion than asteroids and meteorites falling on the Moon - flashes of electricity, according to their calculations, evaporate and destroy about 6.5 thousand tons of regolith every year. Traces of these lightning, as scientists hope, will be found in samples of regolith from "Apollo" and in materials that will collect future expeditions to the moon.