Is the Sun continually creating water on our moon?

It's an interesting concept from NASA's Goddard Space Flight center, and relayed by Space.com. 

The sun is the continuous source of the streams of particles that have come to be called the solar wind.  The intensity of that wind varies over the 11 year solar cycle and on much shorter time scales but the solar wind is always present at some speed or intensity.  

There have been predictions since the 1960s that solar wind could create water on the moon.  In 2016, a NASA probe called  LADEE found that micrometerorite impacts on the moon release water.  When a speck of comet debris strikes the moon, it vaporizes on impact, creating a shock wave in the lunar soil. With a sufficiently large impactor, this shock wave can breach the soil’s dry upper layer and release water molecules from a hydrated layer below.

Now, in the most realistic lab simulation of this process yet, NASA-led researchers have confirmed the solar wind prediction.  

The high-speed particles, primarily composed of positively charged hydrogen ions, capture lunar electrons to become hydrogen atoms. The newly-formed hydrogen atoms then migrate through the dusty and rocky regolith to bond with oxygen, forming hydroxyl and water molecules across the surface, often concentrating in permanently shadowed polar regions. However, the natural cycle and renewability of these ingredients remained unclear. So, to shed light on this process, Li Hsia Yeo, a planetary scientist at NASA's Goddard Space Flight Center in Maryland, led a lab experiment observing the effects of simulated solar wind on two samples of loose regolith brought to Earth by the Apollo 17 mission. [NOTE: hydroxyl is "half a water molecule", (OH^-) the other half being the H⁺ from the solar wind.  SiG]

Since these samples have been on Earth since 1972, the researchers took steps to ensure they were still valid, drying them out to ensure any water they find was created in the experiment, and built their needed custom test equipment.

To remove any terrestrial water the 50-year-old samples would have absorbed since their return to Earth, Yeo and her team baked the samples overnight in a vacuum furnace. To mimic conditions on the moon, the researchers built a custom apparatus that included a vacuum chamber, where the samples were placed, and a tiny particle accelerator, which the scientists used to bombard the samples with hydrogen ions for several days.

In the end, the most useful method they had to detect water was infrared emissions from the Apollo 17-collected regolith being hit with the high energy hydrogen.  The team saw a drop in the light signal that bounced to their detector precisely at the point in the infrared region of the electromagnetic spectrum — near 3 microns — where water typically absorbs energy, leaving a telltale signature.  

While they can’t conclusively say if their experiment made water molecules, the researchers reported in their study that the shape and width of the dip in the wavy line on their graph suggests that both hydroxyl and water were produced in the lunar samples. 

One of the experiment's team members put it this way:

“It took a long time and many iterations to design the apparatus components and get them all to fit inside,” said McLain, “but it was worth it, because once we eliminated all possible sources of contamination, we learned that this decades-old idea about the solar wind turns out to be true.” 

Image capture from NASA Goddard's article on the experiments.  Water being released from the moon during meteor showers, when micrometeoroid impacts breach the dry lunar surface and eject water molecules from a hydrated layer below.  The blue haze above the soil and in the cross section is intended to show water.  Image credit: NASA video.