Ancient moon volcanoes may one day provide astronauts with drinkable water

At the lunar poles, temperatures are low enough for water ice formations to remain stable over lengthy timeframes. However, the origins, amount, and distribution of water ice are unknown. Volcanism on the moon, which occurred billions of years ago, is one possible water source.

A new study from CU Boulder looks into whether volcanic outgassing is a plausible source of lunar polar water ice accumulation. Scientists discovered that lunar volcanism had a long-term impact on the lunar surface: The moon's poles are dotted with ice sheets. In some locations, these sheets are dozens, if not hundreds, of feet thick.

Long before complex life evolved on Earth, scientists built a model to simulate circumstances on the moon. According to the model, previous lunar volcanic eruptions ejected massive amounts of water vapor. These water vapors condense on the lunar surface, generating ice deposits that may yet exist in lunar craters.

“It’s a potential bounty for future moon explorers who will need water to drink and process into rocket fuel. It’s possible that you have big sheets of ice 5 or 10 meters below the surface," said Paul Hayne, one of the study's co-authors.

The moon was a tumultuous world almost 2 to 4 billion years ago, according to astronomers. During this time, several volcanoes erupted across the land, creating massive lava rivers and lakes.

“They dwarf almost all of the eruptions on Earth,” Hayne added.

These volcanoes are also thought to have ejected vast clouds of carbon monoxide and water vapor, according to a recent study from the Lunar and Planetary Institute in Houston. Following that, the clouds swirled around the moon, possibly generating thin, temporary atmospheres.

Could the same environment have caused the ice on the lunar surface, similar to frost accumulating on the ground after a cold fall night?

To discover out, scientists attempted to place themselves on the moon's surface billions of years ago. They used estimations that the moon erupted once every 22,000 years on average at its peak. They then looked into how volcanic gases would have swirled about the moon, eventually escaping into space. They also realized that the weather had turned frosty.

According to the model, around 41% of the water that erupted during this time period could have solidified as ice in the polar regions, with thicknesses of several hundreds of meters.

“The atmospheres escaped over about 1,000 years, so there was plenty of time for ice to form,” said Andrew Wilcoski, a lead author of the new study and a PhD student in the Department of Astrophysical and Planetary Sciences (APS).

It's possible that there was so much ice on the moon that you might have seen a coating of frost and thick polar ice caps from Earth. About 18 quadrillion pounds of volcanic water could have condensed as ice, according to the researchers. That's more water than Lake Michigan currently has. According to the research, much of that lunar water may still exist today. 

It's not easy to locate those ice cubes, though. The majority of them gathered towards the moon's poles and may have been buried beneath several feet of lunar dust or regolith.

“We really need to drill down and look for it,” Wilcoski added.