While previous observations have indicated millions of tons of ice in the permanently shadowed craters of the moon’s poles, a pair of studies in the journal Nature Astronomy take the availability of lunar surface water to a new level.
The latest discovery is good news for astronauts at future lunar bases who could tap into these resources for drinking and making rocket fuel.
More than 15,400 square miles (40,000 square kilometres) of lunar terrain have the capability to trap water in the form of ice, according to a team led by the University of Colorado’s Paul Hayne. That’s 20 per cent more area than previous estimates, he said.
These ice-rich areas are near the moon’s north and south poles. Temperatures are so low in these so-called cold traps — minus 261 degrees Fahrenheit (minus 163 degrees Celsius) — that they could hold onto the water for millions or even billions of years.
"We believe this will help expand the possible landing sites for future lunar missions seeking water, opening up real estate previously considered 'off limits' for being bone dry," Hayne said in an email to The Associated Press.
Using data from NASA’s Lunar Reconnaissance Orbiter, the researchers identified cold traps as small as a few yards (metres) across and as wide as 18 miles (30 kilometres) and more, and used computer models to get all the way down to micrometers in size.
"Since the little ones are too small to see from orbit, despite being vastly more numerous, we can’t yet identify ice inside them," Hayne said. "Once we’re on the surface, we will do that experiment."
For a second study, scientists used NASA's airborne infrared observatory Sofia to conclusively identify water molecules on the sunlit portions of the moon, just outside the polar regions. Most of these molecules are likely stored in the voids between moon dust and other particles or locked inside glassy volcanic material.
Scientists believe all this water on the moon came from comets, asteroids, interplanetary dust, the solar wind or even lunar volcanic eruptions. They'll have a better idea of the sources “if we can get down on the surface and analyze samples of the ice,” Hayne said.
The lead researcher, Casey Honniball, a postdoctoral fellow at NASA’s Goddard Space Flight Center, said at a news conference that she wanted to make it clear the Sofia study had not found puddles on the moon. Rather, the identified hydrogen and oxygen molecules are so far apart, they are neither in liquid or solid form, she noted.
NASA is under White House direction to put astronauts back on the moon by 2024. The space agency wants its new Artemis moon-landing program to be sustainable, unlike the Apollo program a half-century ago.