When it comes right down to it, the Moon is a pretty hostile environment. It’s extremely cold, covered in electrostatically-charged dust that clings to everything (and could cause respiratory problems if inhaled), and its surface is constantly bombarded by radiation and the occasional meteor. And yet, the Moon also has a lot going for it as far as establishing a human presence there is concerned.
In addition to offering astronauts with extensive research opportunities, scientists have theorized for decades that water ice exists on the lunar surface. But thanks to a new study by a team of NASA-supported scientists, we now have definitive proof that the Moon has an abundant supply of water ice in its polar regions. This news could further fuel NASA and other space agencies plans to build a base there in the coming decades.
The study, titled “Direct evidence of surface exposed water ice in the lunar polar regions“, recently appeared in the Proceedings of the National Academy of Sciences. The study was led by Shuai Li – a postdoctoral researcher at the University of Hawaii – and included members from Brown University, the University of Colorado Boulder, the University of California Los Angeles (UCLA), John Hopkins University, and the NASA Ames Research Center.
The possibility that lunar water ice exists within the permanently-shadowed regions (PSRs) – i.e the cratered polar regions – was first suggested in the 1960s. However, it was not until 2008 that the first lines of evidence for the existence of lunar water began to emerge. These included the study of lunar rock samples that were brought back by the Apollo astronauts, which revealed evidence of water molecules trapped in volcanic glass beads.
Prior to this, NASA scientists had believed that the trace amounts of water they had found in these samples were the result of contamination. It was also in 2008 that India’s Chandrayaan-1 orbiter and its accompanying probes – which included the Indian-designed Moon Impact Probe (MIP) and NASA’s Moon Minerology Mapper (M³) – found indirect evidence of water in the Moon’s southern polar region.
This included evidence of hydrogen in the debris that was released by the MIP after it impacted in the Shackleton Crater. These findings were confirmed by NASA’s Moon Minerology Mapper (M³), which also noted the presence of hydrogen over much of the southern polar region. A year later, NASA’s Lunar Crater Observation and Sensing Satellite (LCROSS) and Lunar Reconnaissance Orbiter (LRO) missions also found evidence of water in the lunar south polar area.
However, none of these missions were able to provide direct evidence of lunar water. Hoping to remedy this, Li and his colleagues consulted data from the M³ mission and compared it to data acquired by the Lunar Orbiter Laser Altimeter (LOLA), Lyman-Alpha Mapping Project and Diviner Lunar Radiometer Experiment aboard the Lunar Reconnaissance Orbiter mission.
What they found were absorption features in the M3 data that were similar to those of pure water ice that had been measured in the laboratory. As Li said in a recent University of Hawaii News release:
“We found that the distribution of ice on the lunar surface is very patchy, which is very different from other planetary bodies such as Mercury and Ceres where the ice is relatively pure and abundant. The spectral features of our detected ice suggest that they were formed by slow condensation from a vapor phase either due to impact or water migration from space.”
This was no easy task, since the M³ mission was designed to measure light being reflected from the illuminated regions on the Moon. However, at PSRs, there is no direct sunlight, which meant that the M³ could only measure scattered light in these areas. This was further complicated by the fact that the Moon has no atmosphere, which means light bouncing around the surface is scattered weakly and produces a weak signal.
“This was a really surprising finding,” said Li. “While I was interested to see what I could find in the M3 data from PSRs, I did not have any hope to see ice features when I started this project. I was astounded when I looked closer and found such meaningful spectral features in the measurements.”
These findings are exciting news for NASA and other space agencies that are hoping to build a lunar outpost, beginning some time in the next decade. These include the ESA’s plan to build an “international lunar village“, which would act as a spiritual successor to the International Space Station (ISS). NASA has also proposed building a lunar base in the next decade, which could be located in the PSRs or in stable lava tubes.
Roscosmos and the Chinese National Space Administration (CNSA) have also announced their own plans for a lunar outpost, which would be the culmination of lunar exploration programs that would see crewed missions sent to the surface by the late 2020s and 2030s. The confirmation that the lunar polar regions have plenty of water ice effectively brings all of these plans closer to reality.
Basically, the strong presence of ice on the surface indicates that there could be far more beneath the surface. Not only could this ice be used to provide the crews of a lunar base with drinking water, but the ice could also be used to manufacture hydrazine fuel. This base could therefore act as a refueling station for missions headed to Mars or farther into the Solar System, potentially shaving billions off the cost of long-duration space missions.
It has been clear for some time that the major space agencies of the world intend for humanity to return to the Moon. However, this time around, they want us to stay there. In addition to developing the necessary technology and components to make this happen, ensuring that there are enough resources for local utilization is also key.
And be sure to check this video about lunar water, courtesy of NASA:
Further Reading: NASA, University of Hawaii News, PNAS