The moon’s surface doesn’t contain much compared to the Earth. There is only dust, rocks and basaltic plains resulting from intense volcanic activity over long periods of the moon’s life. We’ve recently discovered a lot of water bound to the moon’s rocky debris or trapped in volcanic glass, or in sheets of ice at or just below the surface, hidden in craters that hide in perpetual shade near the poles, where the sun’s heat can’t evaporate them.
The source of the water is still unknown. But new research suggests an interesting source for it, events we know have happened on the Moon in the past: volcanoes.
Planetary scientists have long wondered if there could be enough water molecules in the gaseous emissions of ancient moon volcanoes to fall back to the surface and form ice sheets in regions of permanent shadows, and it now seems possible.
“Our model suggests that about 41 percent of the total mass of water erupted in that period may have condensed into ice in the polar regions, several hundreds of meters thick,” wrote a team of researchers led by planetary scientist Andrew Wilkowski of the University of Colorado Boulder.
“Our work suggests that short-lived atmospheres resulting from the impacts permeated the period of volcanic activity in ancient times of the Moon’s age, allowing sufficient insulation of large amounts of ice at the poles, and provision of ice and water vapor temporarily during the day at all altitudes.”
The moon looks calm today, but it was hot and chaotic once. Those dark patches that we see when we look at the full moon are vast plains of igneous rocks that resulted from a period of great volcanic activity that may have begun 4.2 billion years ago, and lasted until about a billion years ago, and most of the activity occurred in the first two billion years of this time frame.
Tens of thousands of volcanoes spewed lava onto the surface of the moon, covering it with volcanic terrain.
Jupiter’s moon Io is the most volcanic body in the Solar System today, with more than 400 known volcanoes.
These eruptions involved huge clouds of volcanic gases, mostly carbon monoxide and water vapor. These gases may have formed thin, temporary atmospheres around the Moon that later dissipated into space. But what if the solar wind did not dissipate all the water vapor, and some of it settled as ice? This is what Wilkowski and colleagues postulate.
The team modeled based on a massive eruption rate every 22,000 years, on average. Then they studied the rate of loss of volcanic gases in space compared to the amount of gases that condensed, solidified and settled on the surface of the moon.
They found that during the lifetime of the atmosphere – about 1,000 years – about 15% of the water settled and formed ice on the night side of the moon, which is equivalent to 8.2 trillion tons of water. Some of this ice has evaporated in sunlight over time, but perhaps enough remains over billions of years to make up a significant proportion of the ice that exists today, according to the researchers.
This does not mean that it is easy to find, as some of it may be buried several meters below the surface of the moon. But some of the water at lower altitudes may have stayed at the surface long enough to react with the minerals there, or was trapped in the volcanic glass that melted when meteorites hit the moon.
Evidence of water on the Moon has previously been found, giving us a starting point to search for evidence to support the theory that ice originated from ancient lunar volcanoes.
Source