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In the Lufthansa Technik hangar at Hamburg airport there is a single aircraft for regular inspection these days: the “Sofia” flying observatory, a 43-year-old Boeing 747SP, will be overhauled at Fuhlsbüttel until early next year.
What is special about the machine is that it carries an infrared telescope and other scientific equipment inside. With them, you can look beyond space on research flights, beyond disturbing water vapor in Earth’s atmosphere. To do this, a large door is opened on the side of the jet through which the 2.7-meter telescope can see outside.
The flying observatory is a joint project of the US space agency NASA and the German Aerospace Center (DLR). However, it has been a topic of discussion for years. The Americans have threatened several times to withdraw from the project. From his point of view, the scientific production in the form of publications was not convincing enough.
On Monday, however, at a press conference that was set on short notice, NASA announced an “exciting new discovery”, as announced in advance, that would not have been possible without further ado without “Sofia.” A team led by Casey Honniball from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, already detected molecular water on the moon’s surface during a measurement flight on August 31, 2018, even in areas of the Earth’s satellite that were to be shone in the sun. The “Sofia” measurements were carried out at Clavius crater in the southern highlands of the moon. It has a diameter of about 225 kilometers, which makes it the second largest crater that can be seen from Earth.
Future missions may be interested in water.
The researchers also report their discovery in the journal “Nature Astronomy.” The corresponding manuscript was already received there last November, but has only now been published. The journal’s scientific reviewers may have requested reviews. The article now reports on water molecules trapped in tiny glass spheres and between grains of moondust. The concentration of the molecules is low: there are 100 to 400 of them for every million other molecules on the surface. And yet: the water is there, even at temperatures of up to 120 degrees Celsius.
“The amount of water that ‘Sofia’ discovered corresponds approximately to the content of a 0.33 liter can of drink spread on the surface of a football field”, explains Alessandra Roy, scientist of the project “Sofia” in the DLR Space Administration . Honniball’s investigation was involved. “The moon remains drier than the deserts on earth, but the amount of water found could be important for future astronautical space missions.”
“We don’t know yet if we can use it as a resource, but knowledge of the water on the moon is key to our exploration plans for ‘Artemis’,” NASA chief Jim Bridenstine tweeted to announce the results.
The US space agency has announced that it will return to the moon with humans in the middle of the decade. Currently, numerous tenders are being held for the necessary technology, which will also be purchased by private companies. The outcome of the presidential elections will also determine how the corresponding “Artemis” program continues. With a possible change of government, as has happened several times in the past, the work of the space agency could be realigned.
It is not entirely clear why the water is still there
Regardless of this, however, the Chinese, for example, are drawn to the moon, and Russia also reports long-term plans. And whoever lands on the terrestrial satellite will endeavor to utilize the resources available there for the mission, because cargo transportation from Earth is extremely expensive. Water would be interesting not only for astronauts, but also as rocket fuel if you want to fly further from the moon into the solar system.
For a good ten years there have been indications that the moon is not as dry and dusty as might be supposed. The “Chandrayaan-1”, “Deep Impact” and “Cassini” space probes have made the corresponding observations. However, in these measurements it was not possible to easily differentiate between water molecules, which consist of two hydrogen atoms and one oxygen, and the so-called hydroxyl radicals, in which only one hydrogen atom and one oxygen atom are connected. This was due to the wavelength of the infrared radiation that was measured at that time. This was characteristic of both water molecules and hydroxyl radicals. The measurements by Honniball and his colleagues were now carried out at a different wavelength, which the researchers believe can be used to identify water as such without question.
“Fascinating and extremely exciting,” is what lunar researcher Harald Hiesinger of the University of Münster calls the results in an interview with SPIEGEL. The study is “done quite smartly” and “adds significantly to the results so far.”
The interesting question is why the water molecules are still there – they would be expected to have evaporated a long time ago due to the sun’s rays and would have to have escaped into space never to be seen again. There are several theories as to why they are still detectable: For one thing, it could be that micrometeorites are constantly carrying small amounts of water to the moon. This could be deposited on the rock. Or, larger impacts carry water upward from the deepest layers of the lunar soil. Another possibility would be that the solar wind carries hydrogen atoms to the moon, which combine with existing hydroxyl radicals to form a water molecule.
And then there’s the ice at the poles
In addition to the finely distributed water molecules in the ground, there are also larger water deposits on the moon, in the form of ice that has survived, for example, in the shaded interior of lunar craters. In another “Nature Astronomy” article, a group of scientists led by Paul Hayne of the University of Colorado at Boulder reports that areas much larger than previously thought could act as so-called cold traps.
This means that so little heat from the sun reaches these places that the ice can persist there permanently. According to the researchers, it is quite cold on about 40,000 square kilometers of the moon’s surface. The team had worked with data from the “Lunar Reconnaissance Orbiter.” By modeling, the researchers found that, from their point of view, the number of small cold traps in particular has been underestimated until now. Chunks of ice could survive even in areas just one centimeter in diameter. “Our results suggest that water trapped at the lunar poles may be more widespread and accessible as a resource for future missions than previously assumed,” he concluded.
