(News from Nanowerk) Hydrogen and oxygen ions escaping from Earth’s upper atmosphere and combining on the moon could be one of the known sources of lunar water and ice, according to new research by scientists at the Institute. University of Alaska Fairbanks Geophysics (Scientific reports“Distribution of the aqueous phase near the poles of the Moon from gravitational aspects”).
The work by Gunther Kletetschka, an associate research professor at the UAF Geophysical Institute, adds to a growing body of research on water at the north and south poles of the moon.
Finding water is key to NASA’s Project Artemis, the planned long-term human presence on the moon. NASA plans to return humans to the moon this decade.
“As NASA’s Artemis team plans to build a base camp at the moon’s south pole, water ions that appeared many eons ago on Earth can be used in the astronauts’ life support system. “, said Kletetschka.
The new research estimates that the moon’s polar regions could contain up to 3,500 cubic kilometers – 840 cubic miles – or more of surface permafrost or subsurface liquid water created from ions that escaped from the earth’s atmosphere. This is a volume comparable to that of Lake Huron in North America, the eighth largest lake in the world.
The researchers based this total on the lowest volume model calculation – 1% of Earth’s atmospheric exhaust reaching the moon.
It is generally believed that a majority of lunar water was deposited by asteroids and comets that collided with the moon. Most took place during a period known as the Late Heavy Bombardment. During this period, around 3.5 billion years ago, when the solar system was around 1 billion years old, it is claimed that the first inner planets and Earth’s moon suffered an unusually heavy impact. asteroids.
Scientists also hypothesize that the solar wind is a source. The solar wind carries oxygen and hydrogen ions, which may have combined and deposited on the moon as water molecules.
Now there is another way to explain how water accumulates on the moon.
The research was published March 16 in the journal Scientific Reports in an article authored by Kletetschka and co-authored by Ph.D. student Nicholas Hasson of the Geophysical Institute and Center for Water and Environmental Research at the UAF at the Institute for Northern Engineering. Several colleagues from the Czech Republic are also among the co-authors.
Kletetschka and his colleagues suggest that hydrogen and oxygen ions are swept into the moon as it passes through the tail of Earth’s magnetosphere, which it does for five days of the moon’s monthly journey around the planet. The magnetosphere is the teardrop-shaped bubble created by the Earth’s magnetic field that shields the planet from much of the continuous flux of charged solar particles.
Recent measurements by several space agencies – NASA, European Space Agency, Japan Aerospace Exploration Agency and Indian Space Research Organization – have revealed significant numbers of water-forming ions present during the transit of the moon through this part of the magnetosphere.
These ions have slowly accumulated since the late heavy bombardment.
The presence of the moon in the tail of the magnetosphere, called the magnetotail, temporarily affects some of the Earth’s magnetic field lines – those that are interrupted and simply recede into space for several thousand miles. Not all Earth field lines are tethered to the planet at both ends; some have only one point of attachment. Think of each of them as a string tied to a pole on a windy day.
The presence of the moon in the magnetotail causes some of these broken field lines to reconnect with their opposite broken counterpart. When this happens, hydrogen and oxygen ions that had escaped Earth rush to these reconnected field lines and are accelerated back to Earth.
The authors of the paper suggest that many of these returning ions hit the passing moon, which has no magnetosphere of its own to repel them.
“It’s like the moon is in the shower – a shower of water ions returning to Earth, falling on the moon’s surface,” Kletetschka said.
The ions then combine to form lunar permafrost. Some of this, through geological processes and other processes such as asteroid impacts, is carried below the surface, where it can become liquid water.
The research team used gravitational data from NASA’s Lunar Reconnaissance Orbiter to study the polar regions as well as several major lunar craters. Abnormalities in subsurface measurements at impact craters indicate locations of fractured rock likely to contain liquid water or ice. Gravity measurements at these underground locations suggest the presence of ice or liquid water, the research paper states.
The latest research builds on work published in December 2020 by four of the new paper’s authors, including Kletetschka.