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| The Lunar Module included a descent stage for descent from lunar orbit and lunar surface landing and an ascent stage for return to lunar orbit. This image, captured from television transmitted to Earth by the parked Apollo 16 Lunar Roving Vehicle, shows the moment the ascent stage engine of the Lunar Module Orion ignited. Hot gas from the engine plume blasted pieces of thermal insulation for kilometers in all directions. Image credit: NASA. |
The Moon owes its lack of atmosphere to the Sun. Solar wind and ultraviolet light ionize gas atoms, making them susceptible to transport by the interplanetary magnetic field. Half the atoms escape into space and the rest are driven into the lunar surface material.
In 1974, in the pages of the prestigious publication Nature, Richard Vondrak of NASA's Goddard Research Center in Greenbelt, Maryland, pointed out that lunar vacuum "is a fragile state that could be modified by human activity." He urged that it be "treated carefully if it is to be preserved."
At the time Vondrak wrote, his concern was not wholly academic. In the early 1970s, not a few engineers within NASA expected that the Space Shuttle would lead to a return to the Moon in the 1980s. A lunar outpost where astronauts would conduct resource extraction and beneficiation experiments and test prototype high-vacuum industrial processes would follow soon after.
Vondrak estimated that each of the six Apollo landing missions had doubled the mass of the Moon's atmosphere. He cited two main sources of Moon pollution: life support gases released from Apollo space suits and the Apollo Lunar Module (LM) cabin and rocket exhaust from the Apollo LM rocket motors. The lunar atmosphere returned to normal after a month, however, leading Vondrak to assert that "small lunar colonies" and modest mining would pose "no lasting hazard to the lunar environment."
If, however, more "vigorous" human activity pumped up the lunar atmosphere to a mass of one billion metric tons, solar wind and ultraviolet light would be unable to ionize more than its outermost fringe. The thin lunar atmosphere would then persist for centuries even if no more gas were added, Vondrak wrote.
Vondrak looked briefly at the far-out prospect of creating an Earth-density atmosphere on the Moon by vaporizing oxygen-rich lunar dirt using nuclear blasts. At the time he wrote, the U.S. nuclear arsenal numbered about 28,000 warheads. He estimated that generating an Earth-density atmosphere would require roughly 10,000 times more warheads than the U.S. possessed. Not surprisingly, Vondrak judged this approach to be impractical.
Source
"Creation of an Artificial Lunar Atmosphere," Richard R. Vondrak, Nature, Vol. 248, 19 April 1974, pp. 657-659.
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What would be the downside of having that layer of thin atmosphere on the Moon?
ReplyDeleteAlso, if we have the industrial output that leads to that much outgassed air, perhaps we'd also have the resources to try and clear it away as well?
MB:
DeleteI'll approach this backwards - the moon's nearly pure vacuum is, in theory, great for making new materials free of contaminants. It's better than the typical industrial vacuum on Earth, and it's everywhere on the Moon. Just open a window.
I'm not sure how we'd clear away escaped gas. Some kind of energy beam to strengthen and accelerate the clearing process Vondrak describes?
Frankly, I'm not sure that the vacuum is worth as much as was believed in 1974, when Vondrak wrote his NATURE paper. Why not do industrial processes on a space station? Of course, the Moon is also a ready source of materials, both for industrial processes and for construction and life support. So, perhaps that would justify lunar industrial processes and, in turn, preservation of the lunar vacuum.
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