There isn’t much, relatively speaking, going on on the Moon. There is dust. There is a rock. There are basaltic plains that resulted from widespread volcanic activity over most of the Moon’s history.
And as we recently discovered, there is water. a lot of water. bound in the lunar regolith. Trapped in volcanic glass. Perhaps even in sheets of ice on or just below the surface, hiding in craters at the poles lurking in permanent shade, where they cannot cope with the heat of the sun.
Where this water came from is still a mystery. But new research points to an intriguing source, a process we know has happened on the Moon a lot in the past: volcanism.
Planetary scientists wonder if there were enough water molecules in the ancient moon’s volcanic gases to retreat to the surface and form layers of ice in a permanent shadow. Now the answer appears to be “yes”.
Our model indicates that [around] 41 percent of total H2A team of researchers led by planetary scientist Andrew Wilkowsky of the University of Colorado Boulder writes in their paper that the mass that erupted during this period could have condensed as ice in the polar regions, up to several hundred meters thick.
“Our work indicates that the volcanically active period of the early Moon would have been punctuated by short-lived impact atmospheres that allowed sequestration of large amounts of water ice at the poles and the temporary diurnal availability of ice and water vapor at all latitudes.”
The moon looks very calm these days, but one day the weather was a mess. Those dark spots you see when you look at a full moon are vast plains of igneous rock, from a period of widespread volcanic activity that probably began 4.2 billion years ago, and lasted until about a billion years ago, with most activity occurring in the first two billion years or so of that time frame. .
Tens of thousands of volcanoes have spewed lava onto the Moon, covering the surface with volcanic landscapes (for example, the most current volcanic body in the Solar System is Jupiter’s moon Io, which contains more than 400 known volcanoes).
In addition, those eruptions would have included huge clouds of volcanic gases, mostly carbon monoxide and water vapor. These could have formed weak, transient atmospheres around the Moon that later dissipated into space. But, Wilkowski and colleagues postulate, what if the water vapor did not completely dissipate in the solar wind? What if some of them settled like frost?
They did the modeling, based on an average supermassive eruption rate of once every 22,000 years. Then they studied the rate at which volcanic gases escaped into space, compared to the amount of condensation, frozen and stable on the moon’s surface.
They found that while the atmosphere lasts—a time period of about 1,000 years—about 15 percent of the water settles and forms frost on the moon’s nocturnal side, about 8.2 quadrillion kilograms (18 quadrillion pounds). The researchers said some of that frost would tolerate sunlight over time, but over billions of years, enough would have been left to form a significant proportion of the ice remaining today.
This does not mean that it will be easy to find. Some of them may be buried meters below the surface of the moon. But some of the water could have remained at the surface at low latitudes long enough to interact with the minerals there, or had been captured in the remelted volcanic glass in meteorite impacts.
Such evidence of past water presence on the Moon has already been identified, giving us a starting point for searching for supporting evidence of ancient volcanic moon frosts. The science is very rad.
The team’s research was published in Planetary Science Journal.