Artist’s concept of the moon in Earth’s magnetic tail, the part of our magnetosphere that extends outward, away from our sun. The moon sweeps into this tail every month at full moon. Image via E. Masongsong / UCLA / EPSS / NASA / GSFC / SVS / Duluth News Tribune.
By Bob King aka AstroBob. Originally published in the Duluth News Tribune on Feb. 16, 2021. Reprinted here with permission.
Finding water on the bald moon is one of the most remarkable discoveries of the post-Apollo era. Satellite mapping has revealed ice in permanently shaded craters on the lunar poles and more recently in Clavius, a prominent crater on the moon near the moon that basks in the sun for two weeks a month. Comets and meteoroids likely delivered the water that eventually frozen to ice, although water-rich lava that erupted from the moon’s distant past may also have contributed.
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Orange earth that the Apollo 17 astronauts stumbled upon contained glass droplets ejected from a volcanic fire fountain 3.64 billion years ago. Subsequent analyzes found water trapped in some of the beads. Image via NASA / Duluth News Tribune.
Back on Earth, scientists found water trapped in volcanic glasses and rocks collected by the Apollo 15 and 17 astronauts. In 2019, NASA’s LADEE (Lunar Atmosphere and Dust Environment Explorer) mission found that the constant stream of micrometeorites (small space rocks) bombarding the moon creates a thin, temporary atmosphere of water vapor. When the particles penetrate at least 8 cm into the surface, the impact of the impact releases water molecules that are attached to minerals in deeper soil that are not exposed to direct sunlight.
To be clear, the moon is far from soaking wet, but it’s not the bone dry place we once thought. In comparison, the driest stretch of the Sahara Desert has 100 times more of the wet stuff than the moon. To fill your 16-ounce water bottle, you should process about a ton of moon soil.
The stream of protons and electrons emitted by the sun, called the solar wind, affects both the Earth (shown here) and the Moon. Protons (hydrogen) in the wind bind with oxygen in the moon’s soil to make water. Image via NASA / Duluth News Tribune.
The sun also helps distill droplets and blobs of lunar water when protons in the solar wind collide with the lunar surface and bind with oxygen atoms in minerals to make H2O. Protons are basically hydrogen atoms that have lost an electron. They are the “H” in H2O. Besides, the same solar wind occasionally connects to Earth’s magnetic field and delivers hordes of protons and electrons that fuel the aurora borealis.
In a new study, a team of scientists found that an “earth wind” of ionized atoms blowing from the polar regions can interact with lunar soil and rocks to make water molecules. H represents hydrogen; He for helium, O for oxygen and N2 for nitrogen. The plus sign means that the atoms or molecules have lost an electron and are positively charged. Image via NASA / Bob King / Duluth News Tribune.
A study published February 1, 2021 in the Astrophysical Journal Letters has discovered that the earth may also play a key role in creating water. Like the electrified particle wind from the sun, Earth has made its own wind from ionized hydrogen, helium, oxygen and nitrogen. “Ionized” means that the atoms have lost an electron and have a positive charge.
Powered by interactions with the solar wind, some ionized atoms and molecules in the planet’s polar atmosphere shoot into space where they are held captive by Earth’s magnetic field, known as the magnetosphere.
Usually the moon stays away from the magnetosphere, which points away from the sun like a weather vane, but travels through it for 3-5 days a month around the time of the full moon. The magnetosphere deflects the solar wind, preventing the sun’s protons from collecting fresh water on the lunar surface. With the moon cut off from its supply, astronomers assumed that lunar water created by solar bombardments would quickly hiss into space and that the moon would emerge from its temporary magnetic shelter all the more drier.
This image of the moon is from NASA’s Moon Mineralogy Mapper on the Indian Chandrayaan-1 probe. Small amounts of water and hydroxyl (related to water) are shown in blue. Most lunar water is concentrated in the colder polar regions. Image via ISRO / NASA / JPL-Caltech / Brown University / USGS.
But no! Using data from the Indian spacecraft Chandrayaan-1, which mapped water in the polar regions of the moon, Chinese researchers made a surprising discovery. The water level remained almost the same every time the moon left the magnetosphere. Something had to throw protons at our satellite to make the water come. Earth’s polar wind seemed the likely suspect.
Additional evidence came from Japan’s Kaguya lunar orbit, active in the early 2000s, which detected scads of positively charged oxygen atoms on the moon every time it hid in the shadow of Earth’s magnetic tail. In addition to hydrogen, oxygen can also contribute to the formation of water on the moon. It’s amazing to consider that ionic breezes from Earth can help cover the lunar surface with life-giving water that may be beneficial to future astronauts.
In short, particles transported from the poles of the Earth through our planet’s magnetosphere can interact with lunar rocks to create small amounts of water on the moon.
Source: Earth wind as a possible exogenous source of lunar surface hydration
Via Duluth News Tribune
