Earth色视频下载檚 atmosphere may be source of some lunar water
Rod Boyce
907-474-7185
April 27, 2022
Hydrogen and oxygen ions escaping from Earth色视频下载檚 upper atmosphere and combining on the moon could be one of the sources of the known lunar water and ice, according to by University of 色视频下载 Fairbanks Geophysical Institute scientists.
The work led by UAF Geophysical Institute associate research professor Gunther Kletetschka adds to a growing body of research about water at the moon色视频下载檚 north and south poles.
Finding water is key to NASA's Artemis project, the planned long-term human presence on the moon. NASA plans to send humans back to the moon this decade.
色视频下载淎s NASA色视频下载檚 Artemis team plans to build a base camp on the moon色视频下载檚 south pole, the water ions that originated many eons ago on Earth can be used in the astronauts色视频下载 life support system,色视频下载 Kletetschka said.
The image shows the distribution of surface ice at the moon色视频下载檚 south pole (left) and north pole (right), detected by NASA色视频下载檚 Moon Mineralogy Mapper instrument in 2009. Blue represents the ice locations, plotted over an image of the lunar surface, where the gray scale corresponds to surface temperature (darker representing colder areas and lighter shades indicating warmer zones). The ice is concentrated at the darkest and coldest locations, in the shadows of craters. This image was the first time scientists directly observed definitive evidence of water ice on the moon色视频下载檚 surface.
The new research estimates the moon色视频下载檚 polar regions could hold up to 3,500 cubic kilometers 色视频下载 840 cubic miles 色视频下载 or more of surface permafrost or subsurface liquid water created from ions that escaped Earth色视频下载檚 atmosphere. That色视频下载檚 a volume comparable to North America色视频下载檚 Lake Huron, the world色视频下载檚 eighth-largest lake.
Researchers based that total on the lowest volume model calculation 色视频下载 1% of Earth色视频下载檚 atmospheric escape reaching the moon.
A majority of the lunar water is generally believed to have been deposited by asteroids and comets that collided with the moon. Most was during a period known as the Late Heavy Bombardment. In that period, about 3.5 billion years ago when the solar system was about 1 billion years old, it is argued that the early inner planets and Earth色视频下载檚 moon sustained unusually heavy impact from asteroids.
Scientists also hypothesize that the solar wind is a source. The solar wind carries oxygen and hydrogen ions, which may have combined and been deposited on the moon as water molecules.
Now there色视频下载檚 an additional way to explain how water accumulates on the moon.
The research was published March 16 in the journal Scientific Reports in a paper authored by Kletetschka and co-authored by Ph.D. student Nicholas Hasson of the Geophysical Institute and UAF Water and Environmental Research Center at the Institute for Northern Engineering. Several colleagues from the Czech Republic are also among the co-authors.
Kletetschka and his colleagues suggest hydrogen and oxygen ions are driven into the moon when it passes through the tail of the Earth色视频下载檚 magnetosphere, which it does on five days of the moon色视频下载檚 monthly trip around the planet. The magnetosphere is the teardrop-shaped bubble created by Earth色视频下载檚 magnetic field that shields the planet from much of the continual stream of charged solar particles.
Recent measurements from multiple space agencies 色视频下载 NASA, European Space Agency, Japan Aerospace Exploration Agency and Indian Space Research Organization 色视频下载 revealed significant numbers of water-forming ions present during the moon色视频下载檚 transit through this part of the magnetosphere.
This diagram from the research paper authored by Gunther Kletetschka shows the moon approaching Earth's magnetotail.
These ions have slowly accumulated since the Late Heavy Bombardment.
The presence of the moon in the magnetosphere色视频下载檚 tail, called the magnetotail, temporarily affects some of Earth色视频下载檚 magnetic field lines 色视频下载 those that are broken and which simply trail off into space for many thousands of miles. Not all of Earth色视频下载檚 field lines are attached to the planet at both ends; some have only one attachment point. Think of each of these as a thread tethered to a pole on a windy day.
The moon色视频下载檚 presence in the magnetotail causes some of these broken field lines to reconnect with their opposing broken counterpart. When that happens, hydrogen and oxygen ions that had escaped Earth rush to those reconnected field lines and are accelerated back toward Earth.
The paper色视频下载檚 authors suggest many of those returning ions hit the passing moon, which has no magnetosphere of its own to repel them.
色视频下载淚t is like the moon is in the shower 色视频下载 a shower of water ions coming back to Earth, falling on the moon色视频下载檚 surface,色视频下载 Kletetschka said.
The ions then combine to form the lunar permafrost. Some of that, through geologic and other processes such as asteroid impacts, is driven below the surface, where it can become liquid water.
The research team used gravitational data from NASA色视频下载檚 Lunar Reconnaissance Orbiter to study polar regions along with several major lunar craters. Anomalies in underground measurements at impact craters indicate locations of fractured rock conducive to containing liquid water or ice. Gravity measurements at those subsurface locations suggest the presence of ice or liquid water, the research paper reads.
The latest research builds on work published in December 2020 by four of the new paper's authors, including Kletetschka.
ADDITIONAL CONTACTS: Gunther Kletetschka, 907-474-7090, gkletetschka@alaska.edu; Nicholas Hasson, nhasson@alaska.edu
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