Billions of years ago, a series of volcanic eruptions raged across the moon, blanketing hundreds of thousands of square kilometers of the orb’s surface in hot lava. Over the eons, this lava created the dark spots, or maria, that give the face of the moon its distinctive appearance today.
Now, new research from the University of Colorado at Boulder (CU Boulder) suggests that volcanoes may have left another lasting impact on the lunar surface: patches of ice that dot the moon’s poles and, in some places, could measure tens or even hundreds of feet. thick.
“We think of it as frost on the moon that has built up over time,” said Andrew Wilcoski, lead author of the new study and a graduate student in the Department of Astrophysical and Planetary Sciences (APS) and the Laboratory of atmospheric and space physics. (LASP) at CU Boulder.
He and his colleagues published their findings this month in The Journal of Planetary Science.
The researchers relied on computer simulations, or models, to try to recreate conditions on the moon long before complex life appeared on Earth. They discovered that ancient lunar volcanoes spewed out huge amounts of water vapor, which then settled on the surface, forming reserves of ice that could still be hiding in lunar craters. If humans had been alive at the time, they might even have seen a sliver of this frost near the border between day and night on the surface of the moon.
That’s a potential bounty for future lunar explorers who will need water to drink and turn into rocket fuel, said study co-author Paul Hayne.
“It’s possible that 5 or 10 meters below the surface you have large patches of ice,” said Hayne, an assistant professor in APS and LASP.
The new study adds to a growing body of evidence that suggests the moon could be flooded with far more water than scientists once thought. In a 2020 study, Hayne and his colleagues estimated that nearly 6,000 square miles of the lunar surface may be able to trap and cling to ice, mostly near the moon’s north and south poles. Where all this water came from in the first place is unclear.
“There are a lot of potential sources right now,” Hayne said.
Volcanoes could be big. The planetary scientist explained that 2-4 billion years ago, the moon was a chaotic place. Tens of thousands of volcanoes erupted on its surface during this time, generating huge lava rivers and lakes, much like the features you might see in Hawaii today, but much larger.
“They dwarf nearly all eruptions on Earth,” Hayne said.
Recent research by scientists at the Lunar and Planetary Institute in Houston shows that these volcanoes likely also ejected towering clouds composed primarily of carbon monoxide and water vapor. These clouds then swirled around the moon, potentially creating thin, short-lived atmospheres.
This led Hayne and Wilcoski to wonder: Could this same atmosphere have left ice on the lunar surface, much like frost forming on the ground after a cold autumn night?
To find out, the duo alongside LASP associate researcher Margaret Landis set out to try to get to the surface of the moon billions of years ago.
The team used estimates that, at its peak, the moon erupted every 22,000 years, on average. The researchers then tracked how volcanic gases may have swirled around the moon, escaping into space over time. And, they found, conditions may have turned freezing.
According to the group’s estimates, about 41% of the water in volcanoes may have condensed on the moon as ice.
“The atmospheres escaped over about 1,000 years, so there was plenty of time for the ice to form,” Wilcoski said.
There may have been so much ice on the moon, in fact, that you could, in theory, spot the glow of frost and thick, polar ice caps from Earth. The group calculated that about 18 quadrillion pounds of volcanic water could have condensed as ice during this time. That’s more water than there is currently in Lake Michigan. And research suggests that much of that lunar water may still be present today.
These space ice cubes, however, won’t necessarily be easy to find. Most of this ice likely accumulated near the moon’s poles and may be buried under several feet of lunar dust, or regolith.
One more reason, Hayne said, for people or robots to come back and start digging.
“We really have to dig and search,” he said.
Reference: “Polar Ice Accumulation from Volcano-Induced Transient Atmospheres on the Moon” by Andrew X. Wilcoski, Paul O. Hayne, and Margaret E. Landis, May 3, 2022, The Journal of Planetary Science.