For the first time, scientists have uncovered direct evidence of water ice on the surface of the moon’s polar regions. And the ice itself could be ancient, according to a study published Monday in the Proceedings of the National Academy of Sciences.
Scientists from the University of Hawaii and Brown University and Richard Elphic from NASA’s Ames Research Center used data from NASA’s Moon Mineralogy Mapper instrument to make the discovery. The instrument is on the Indian Space Research Organization’s Chandrayaan-1 spacecraft, India’s first lunar probe, which launched in 2008.
The instrument was designed to search for distinct signatures that prove the presence of water ice on the surface of the moon. This included gathering data that not only detected ice’s reflective properties, but the way the molecules absorb infrared light — which tells the difference between water and ice.
Previous studies of the lunar poles suggested that ice could be present there, but the possible signs could have been explained due to other phenomenon as well.
The ice is in the darkest and coldest areas at the poles, in shadows of craters where sunlight never reaches due to the tilt of the moon’s axis. The warmest temperatures in these areas don’t go above negative-250 degrees Fahrenheit.
At the southern pole, the ice can be found in craters. At the northern pole, the ice is widely spread, but more sparse. This odd distribution could mean that there is a low water supply rate, or imply that the ice itself is millions of years old with little accumulation since then.
“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,” Shuai Li, lead study author and postdoctoral researcher at the Hawaii Institute of Geophysics and Planetology, said in a statement. “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.”
Further observation and study could reveal more about the moon’s evolution process as well.
It’s possible that this surface ice could be a water source for future moon mission, and easier to access than any water believed to be beneath the moon’s surface.
“Given that the Moon is our nearest planetary neighbor, understanding the processes which led to water ice on the Moon provides clues to understand the origin of water on Earth and throughout the solar system,” said Li. “A future Moon mission is needed to examine the whole lunar PSRs [permanently shaded regions] to map out all water ices and understand the processes which led to water on the Moon. This work provides a roadmap for future exploration of the Moon, particularly the potential of water ice as a resource.”