“This discovery reveals that water might be distributed across the lunar surface and not limited to the cold shadowed places near the lunar poles,” Paul Hertz, the director of NASA’s astrophysics division, said during a news conference on Monday.
Although that water could be difficult to collect by astronauts, another group of researchers also reported on Monday that in addition to big, frigid, deep and potentially treacherous craters in the moon’s polar regions, smaller and shallower depressions in the same areas may also be cold enough to hold onto water ice for millions, if not billions, of years. These small water ice deposits could be a “real game changer,” Paul O. Hayne, a professor of astrophysical and planetary sciences at the University of Colorado, who led that research, said in an interview. “It could make it much more accessible to future astronauts and rover missions.”
The moon’s South Pole has become a desired destination for a number of robotic missions by NASA, China and other space programs. Such ice might not only provide water for future astronauts to drink, but water molecules can also be broken apart into their constituent hydrogen and oxygen atoms. The oxygen would give the astronauts something to breathe. Hydrogen and oxygen can also be used as rocket propellant for trips home to Earth or even some day to Mars and beyond.
“Anytime we don’t need to pack water for our trip, we have an opportunity to take other useful items with us,” said Jacob Bleacher, chief exploration scientist for the NASA’s human exploration and operations directorate.
In the observations taken by NASA’s flying telescope, scientists were able to observe a wavelength of infrared light, at six microns, emitted by water molecules. Those emissions were seen in sunlit parts of the Clavius crater near the South Pole but not near the lunar Equator where temperatures get warmer. Observations by spacecraft a decade ago had also suggested a more widespread distribution of water on the moon. Those measurements focused on a shorter, three-micron wavelength that was more ambiguous, unable to differentiate between a water molecule, which consists of two hydrogen atoms and one oxygen atom or hydroxyl, which has one hydrogen atom and one oxygen atom.
“Hydroxyl is actually the active ingredient in drain cleaners,” said Casey I. Honniball, a postdoctoral researcher at NASA’s Goddard Spaceflight Center in Greenbelt, Md., and lead author of the study that used SOFIA. “Hypothetically, if drain cleaner were on the moon, we could not tell the difference between the drain cleaner and water using the three-micron wavelength.”
The six-micron emissions are a “distinct chemical fingerprint” for water, Dr. Honniball said. These observations cannot be performed from Earth’s surface because there is too much water in the lower
atmosphere. Also, no lunar spacecraft, present or planned, has an instrument to examine this particular wavelength.
But SOFIA can. The aircraft, NASA’s Stratospheric Observatory for Infrared Astronomy, is a 747 with a sliding door that opens to allow a 106-inch, 17-ton telescope to peer into the night sky. But the
observatory, a collaboration between NASA and the German Aerospace Center that has been in operation since 2010, is expensive, and the Obama and Trump administrations both sought to end the program. Each time, Congress has restored financing and SOFIA has continued flying.
Kenneth Chang is a science reporter with NYT©2020
The New York Times