NASA's Stratospheric Observatory for Infrared Astronomy (SOFIA) has for the first time confirmed the presence of water on the Moon's side illuminated by the Sun, reports Nature Astronomy.
SOFIA is a joint project of NASA and the German Center for Aviation and Astronautics. Equipped with a telescope approximately 270 cm in diameter, the modified Boeing 747SP Jetliner enables astronomers to study the solar system and more in a way that is not possible with ground-based telescopes. Flying over 13 kilometres, the plane rises above the atmospheric water vapour (or rather 99% of that vapour) to get a clearer infrared picture of the universe.
Using its Faint Object infrared camera connected to the telescope (FORCAST), SOFIA was able to capture a water-molecule-specific wavelength (6.1 microns) and discovered it in the sunlit lunar Clavius crater.
Clavius, which is located in the southern hemisphere of the moon, is one of the largest craters visible from Earth. Earlier observations of the lunar surface have detected some form of hydrogen, but have not been able to distinguish water from its resemblance to hydroxyl (OH). Data from Clavius revealed the presence of water at concentrations ranging from 100 to 412 parts per million - roughly just over 1/3 of a litre per cubic meter of soil on the lunar surface.
For comparison, there is 100 times more water in the sand of the Sahara than in the lunar soil studied by Sofia. The discovery raises new questions about how water is produced and persists on the lunar's raw, airless surface. According to experts, water may be present on the surface of the moon not only in cold, shady places.
"We had indications that water might be present on the sunlit side of the Moon," said Paul Hertz, director of the Astrophysics Division at NASA's Directorate of Science Missions in Washington. Now we know it's there. This discovery challenges our understanding of the lunar surface and raises intriguing questions about resources relevant to space exploration. '
Water is a precious resource in space and a key component of life as we know it. It is not known whether the one discovered on the moon will be easy to exploit. As part of the Artemis program, NASA wants to learn all about the presence of water on the moon before sending more people to its surface in 2024 and establishing a permanent human presence there by the end of the decade.
"Before the SOFIA observations, we knew there was some type of hydration," said Casey Honniball, lead author who published the results of her thesis at the University of Hawaii at Manoa in Honolulu. "But we didn't know how many, if any, were water molecules - the kind we drink every day - or something more like a pipe cleaner."
"Without a dense atmosphere, the water on the moon's sunlit surface should just disappear into space," said Honniball, who is now a PhD research fellow at Goddard Space Flight Center in Greenbelt, Maryland. “But we can see something. Something produces water and something has to trap it there, ”she added.
Several forces can be involved in providing or creating this water. A rain of micrometeorites carrying a small amount of water can deposit water on the lunar surface when it hits it. Another possibility is a two-step process in which the solar wind from the sun delivers hydrogen to the lunar surface and causes a chemical reaction with oxygen-containing minerals in the soil to form hydroxyl. In the meantime, radiation from the bombardment of micrometeorites may change.
SOFIA results build on years of previous research into the presence of water on the moon. When Apollo astronauts first returned from the moon in 1969, it was considered completely dry. Orbital and impact missions over the past 20 years, such as NASA's Lunar Crater Observation and Detection, have confirmed the presence of ice in constantly shaded craters around the Moon's poles.
Meanwhile, several spacecraft - including the Cassini mission and the Deep Impact comet mission, as well as the Indian Space Research Organization's Chandrayaan-1 mission - and the NASA ground-based Infrared Telescope, have looked around the moon's surface and found evidence of hydration in the sunny regions. However, these missions were unable to definitely distinguish the form in which he was present - neither H2O nor OH.
In the same issue of Nature Astronomy, scientists published a paper using theoretical models and data from NASA's Lunar Reconnaissance Orbiter, indicating that water may be trapped in somewhat shaded areas where temperatures remain below freezing over more of the Moon than is currently expected.
"Water is a valuable resource, both for scientific purposes and for use by our explorers," said Jacob Bleacher, chief exploration scientist at NASA's Human Exploration and Missions Directorate. "If we are able to use the resources of the moon, we will be able to take less water and more equipment to enable new scientific discoveries" - he pointed out. (PAP)
Author: Paweł Wernicki