Water on the Moon – October 28, 2020


In some more exciting space news, a team of scientists found evidence for widespread presence of water molecules on the Moon! This is exciting as lunar exploration continues – and lunar bases may soon become a reality. Water on the Moon simplifies what needs to be brought from Earth: ice can provide astronauts with water to drink and water molecules can be broken apart into hydrogen and oxygen atoms and formulated into rocket fuel for missions to Mars and beyond.
To confirm water on the Moon, measurements can’t be done accurately from Earth’s surface because there is too much water in the lower atmosphere that interferes with the signal. No current lunar spacecraft has the right instrument to look for the molecules, either. Instead, scientists used NASA’s telescope, SOFIA (Stratospheric Observatory for Infrared Astronomy) which flies at 45,000 feet in a 747 equipped with an opening sliding door to allow the telescope to make its observations. Flying so high means the telescope can make accurate measurements, as its above 99.9% of the water vapor in our atmosphere.
In the past, measurements of the lunar surface focused on a specific wavelength of light (at 3 microns) to search for the presence of water. But the signal at that wavelength can also be attributed to hydroxyl (OH instead of H2O). Scientists needed more evidence to confirm the distinct “chemical fingerprint” for water. There is an unambiguous feature found at 6 microns in the infrared part of the electromagnetic spectrum that is tied specifically to water – and SOFIA was able to spot it!
What has been found are not puddles of water in deep shadowed craters on the Moon. Rather, water molecules are so spread apart that they do not form ice OR liquid water in these regions (note: in permanently shadowed craters near the lunar poles, scientists HAVE discovered deposits of water ice). The heat of the Sun simply wouldn’t allow water to persist – and yet, based on these findings, it does. How is this possible? Scientists hypothesize that the water molecules are more diffuse and may actually be trapped within glass beads in the soil. When you have a micrometeorite impact on the Moon, this melts some of the lunar soil which then cools quickly and forms glass. If water is already present – formed during or delivered during impact – that water can then get captured in the structure of the glass.
It remains to be known just how easy it will be to extract water from these glass beads. But imagine that we do finally establish a permanent presence on the Moon, thanks in part to these water molecules. Future lunar exploration could be expanded to the frigid -400-degree Fahrenheit polar craters which house water ice deposits. On Earth, layers of accumulated ice (ice cores) tell us about our past climate. Extracting a lunar ice core could provide us with a unique historical record of solar system conditions by revealing more about the nature of the ice delivered via ancient comets. And if we find organics in the ice, it might even help us understand the origin of life on planet Earth. These are exciting times!
photo: U. Horodyskyj, Rice University campus observatory