by Dr. Tony Phillips
An artist's concept of Earth wind (blue)
Every day, 24/7, a breeze of electrified gas blows away from the sun
faster than a million mph.
Solar wind sparks
beautiful auroras around the poles of Earth, sculpts the tails
of comets, and scours the surface of the Moon.
Would you believe, Earth
is windy, too...?
Our own planet produces a breeze of electrified gas. It's like the
solar wind, only different, and it
may have important implications for space weather on
"Earth wind" comes from the axes of our planet.
Every day, 24/7, fountains of gas shoot into space
from the poles.
The leakage is tiny compared to Earth's total atmosphere, but it is
enough to fill the magnetosphere with a riot of rapidly blowing
Once a month, the Moon
gets hit by a blast of Earth wind.
It happens around the time of the full Moon when Earth's magnetic
tail points like a shotgun toward the lunar disk.
For 3 to 5 days,
lunar terrain is bombarded by,
O+, N2+ and other particles...
One effect of Earth wind,
just discovered, is to create water...
According to a new study (Earth
Wind as a Possible Exogenous Source of Lunar Surface Hydration)
published in the January 2021 edition of the Astrophysical
Journal Letters, Earth wind can actually make H2O on
the lunar surface.
"Hydrogen ions in
Earth wind combine with oxygen in Moon rocks and soil to make
hydroxyl (OH–) and water (H2O)," explains
one of the lead authors, Quanqi Shi of Shandong University and
the Chinese Academy of Sciences.
"This came as a surprise."
Researchers have long
known that hydrogen from space raining down on the Moon can create a
temporary form of surface water.
Solar wind does it
all the time...
However, this kind of
water was expected to dry up once a month when the Moon enters
Earth's magnetic tail.
Terrestrial magnetism deflects solar wind, turning the faucet to the
OFF position. But that's not what happened...
The researchers looked at data from NASA's Moon Mineralogy Mapper
(M3) onboard India's
spacecraft, which was orbiting the Moon in 2009 when the Moon made
multiple passes through Earth's magnetic tail.
"We found that lunar
surface water does not disappear as expected during the
magnetosphere shielding period," says Shi.
"Earth wind must be bridging the gap."
Above: Sample Chandrayaan-1
observations of lunar surface water
In fact, when it comes to producing water, Earth wind has some big
advantages over solar wind.
When the full Moon is inside Earth's magnetic tail, it is surrounded
by Earth wind and feels its impact from every direction.
The lunar nearside, lunar farside, and lunar poles are all peppered
with Earth wind particles. In this sense, Earth wind can potentially
make water anywhere - unlike the solar wind which rains down only on
the lunar dayside.
Another potential advantage of Earth wind:
It is oxygen rich,
much more so than solar wind.
another key element of water," points out Shi.
"Whether these oxygen ions can contribute to the formation
of lunar water is a very intriguing question for future