MOON ATMOSPHERE FORMATION!

• The idea of terraforming the Moon, giving it as Earth-like an environment as possible given its low mass and gravity and long day/night cycle, is evocative. Certainly it has produced some stunning conceptual imagery.
• Pumping gas onto the Moon's surface--releasing gases like oxygen locked up in the Moon's surface material--wouldn't work by itself. Our nearest non-Earthly world is critically short in any number of elements vital to life, like nitrogen, and water. More ambitious methods would be needed. This past July, Gregory Benford wrote an article for Slate ("A Terraformed Moon Would Be an Awful Lot Like Florida") wherein he proposed bombarding the Moon with comets in order to give it the volatiles, including water and air, necessary for an Earth-like environment.

"The process begins by steering a comet nucleus, which some  call an iceteroid, from the chilly freezer beyond Pluto. Nudge it from  its slow orbit with a mile-per-second velocity change and swing it near  any gas giant planet for a momentum swerve. By hooking the comet  adroitly in a reverse swing-by around, say, Jupiter, we can loop it into  an orbit opposite to the way that worlds orbit the sun. The grimy,  mountain-size iceteroid soon will loom in the moon’s night sky.

Mere days before it strikes, scientists will have to blow it  apart—brutally and carefully. Ice shards come gliding in all around the  moon’s equator, small enough that they cannot free themselves from  gravity’s grip. (We can’t let big chunks of comet scatter off the moon  to rain down as celestial buckshot on Earth.) Within hours of the first  incoming comet, the moon will have a crude atmosphere. With one-sixth of  Earth's gravity, it can hold gases for tens of thousands of years.

As more comets arrive and pellets pelt down, the moon spins  faster. From its lazy “day” cycle of 28 days, it speeds up to a 60  hours—close enough to Earthlike, as they say, for government work."

There are major problems with this. The most obvious is that aiming large numbers of high-velocity comets at the Earth-Moon system has the potential to go very badly wrong if one of them is off-target. The number of impacts it would take to break the Moon's tidal lock with the Earth, meanwhile, could be very large. Breaking the tidal lock itself might have negative effects on the Earth.

Perhaps most importantly for our purposes, if the Moon was given an atmosphere and a hydrosphere, it would create massive and ongoing selenological instability and a hostile environment, both things we have no idea how to solve. This analysis gives an idea.

"The upper few kilometers of the lunar surface contain several times 1018 kg of iron(II) which in the presence of water would readily react with oxygen to form iron(III). Such an amount of iron(II) could easily absorb all of the oxygen in the Earth atmosphere.

A large fraction of the Moons crust consists of oxides of calcium, magnesium, and iron(II), which in the presence of water would react to form hydroxides that would (partly) dissolve in the forming seas to create a poisonously alkaline fluid, with pH 10--11. If enough oxygen were available to oxidize the dissolved iron(II)hydroxides, insoluble iron(III)hydroxides would precipitate on the sea floors and shores, creating vast quantities of slightly poisonous, orange mud. Such reactions would be violent and fast in the upper part of the crust, but their rate would decrease with increasing depth. The oxidizing, hydration, and other processes would continue for ages. In the meantime oxygen and other pressures would not be stable. Most of important all: the absorption of such enormous amounts of oxygen, water, by the upper part of the crust of the Moon would make the rocks expand by perhaps as much as ten percent or more. One can wonder if such expansion would be a tranquil process. It could create strong quakes for possibly many thousands of years."

Hopefully conditions on the Moon would stabilize before its acquired atmosphere vanished into space. Conceivably large-scale engineering might speed up this process, but the scale of the reengineering of the Moon required would make Venus terraforming easy!