First proof that water can be created on the lunar surface by the Earth’s magnetosphere

75% of its orbit in the solar wind (yellow), which is blocked by the magnetosphere the rest of the time. Credit: E. Masongsong, UCLA EPSS, NASA GSFC SVS.” width =”800″ height =”496″/>

Before the Apollo era, the moon was thought to be dry like a desert due to the extreme temperatures and harshness of the space environment. Numerous studies have since discovered lunar water: ice in shaded polar craters, water bound to volcanic rocks, and unexpected rusty iron deposits in the lunar soil. Despite these findings, there is still no real confirmation of the extent or origin of lunar surface water.

The dominant theory is that the positively charged hydrogen ions propelled by the solar wind bombard the lunar surface and react spontaneously to produce water (as hydroxyl (OH^–) and molecular (H₂O)). However, a new multinational study published in Letters from the Astrophysical Journal suggests that the solar wind is not the only source of ions forming water. The researchers show that particles from Earth can also seed the moon with water, implying that other planets could also supply water to their satellites.

Water is much more widespread in space than astronomers initially thought, from the surface of Mars to the moons of Jupiter, including Saturn’s rings, comets, asteroids and Pluto; it has even been detected in clouds far beyond our solar system. It was previously assumed that water was incorporated into these objects during the formation of the solar system, but it is increasingly evident that water in space is much more dynamic. Although the solar wind is a likely source of lunar surface water, computer models predict that up to half of it should evaporate and disappear in high latitude regions for about three days of full moon when it passes through the earth’s magnetosphere.

Surprisingly, the latest analysis of hydroxyl surface / water surface maps by the Moon Mineralogy Mapper from the Chandrayaan-1 satellite (M³) has shown that lunar surface water does not disappear during this period of protection of the magnetosphere. It was believed that the Earth’s magnetic field prevented the solar wind from reaching the moon so that water could not be regenerated faster than it was lost, but the researchers found that was not the case.

By comparing a time series of water surface maps before, during and after the transit of the magnetosphere, the researchers argue that lunar water could be replenished by fluxes of magnetospheric ions, also known as “earth winds.” The presence of these Earth-derived ions near the moon has been confirmed by the Kaguya satellite, while THEMIS-ARTEMIS satellite observations have been used to profile the distinctive characteristics of ions in the solar wind versus those of the earth wind. of the magnetosphere.

Previous observations of the Kaguya satellite during the full moon detected high concentrations of oxygen isotopes that escaped from the Earth’s ozone layer and drowned in the lunar soil, as well as an abundance of ions hydrogen in the vast extended atmosphere of our planet, called the exosphere. These combined fluxes of magnetosphere particles are fundamentally different from those of the solar wind. So the latest detection of surface water in this study refutes the shielding hypothesis and instead suggests that the magnetosphere itself creates a “water bridge” that can replenish the moon.

The study used a multidisciplinary team of experts in cosmochemistry, space physics and planetary geology to contextualize the data. Previous interpretations of surface water did not take into account the effects of the Earth’s ions and did not examine how surface water changed over time. The only surface maps and particle data available during a full moon in the magnetosphere were in winter and summer 2009, and it took several years to analyze and interpret the results. Analysis was particularly difficult due to the sparse observations, which were needed to compare the same lunar surface conditions over time and to monitor temperature and surface composition.

In light of these results, future studies of solar wind and planetary winds may reveal more about the evolution of water in our solar system and the potential effects of solar and magnetosphere activity on other moons and planetary bodies. Expansion of this research will require new satellites equipped with full hydroxyl / water mapping spectrometers and particle sensors in orbit and on the lunar surface to fully confirm this mechanism. These tools can help predict the best regions for future exploration, mining, and eventual colonization on the moon. In practice, this research can influence the design of future space missions to better protect humans and satellites from the risks of particle radiation, and also improve computer models and laboratory experiments on water formation in the world. ‘space.