'Exciting' news from SOFIA, about the Moon Options

[marsbug]

This has just popped up in my news feed: NASA will be making an 'exciting' announcement regarding SOFIA observations of the Moon on the 26th... And that's more or less all we've got. Given what we know about the wavelengths SOFIA uses, and observation campaigns it's been used for that might be relevant to the Moon, I wondered if anyone might have any insight?

[marsbug]

The SOFIA related paper from the announcement:

Molecular water detected on the sunlit Moon by SOFIA

Widespread hydration was detected on the lunar surface through observations of a characteristic absorption feature at 3 µm by three independent spacecraft1,2,3. Whether the hydration is molecular water (H2O) or other hydroxyl (OH) compounds is unknown and there are no established methods to distinguish the two using the 3 µm band4. However, a fundamental vibration of molecular water produces a spectral signature at 6 µm that is not shared by other hydroxyl compounds5. Here, we present observations of the Moon at 6 µm using the NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA). Observations reveal a 6 µm emission feature at high lunar latitudes due to the presence of molecular water on the lunar surface. On the basis of the strength of the 6 µm band, we estimate abundances of about 100 to 400 µg g−1 H2O. We find that the distribution of water over the small latitude range is a result of local geology and is probably not a global phenomenon. Lastly, we suggest that a majority of the water we detect must be stored within glasses or in voids between grains sheltered from the harsh lunar environment, allowing the water to remain on the lunar surface.

[abalone]

The SOFIA related paper from the announcement:

100-400g per ton of regolith, possibly only 1L for every 10T, not a lot. The news media is overblowning the significance. Unlikely to be able to collect enough economically to produce rocket fuel.

[Xerxes]

100-400g per ton of regolith, possibly only 1L for every 10T, not a lot. The news media is overblowning the significance. Unlikely to be able to collect enough economically to produce rocket fuel.

Of course, you don't have to sample random patches of lunar regolith when you're trying to mine water. The paper indicates that most of the water is expected to be found in glassy ejecta, where it occurs in concentrations up to 1300 µg/g. You would simply set down your solar-powered mining apparatus in the region of highest concentration. Compared to finding or transporting power into a permanently shadowed crater, it may be much more convenient.

[marsbug]

I think it's fair to say that is possible, but we don't know it's true at this (what is in fact still quite early) stage in the investigation. I'd be surprised if there weren't regions of hogher concentration, as distributions of things in nature tend to be patchy, at least on some scale. But at this point all we can say is that this is probably enough data to justify in-situ follow up investigations - which are already planned. Judgement either way on practical fuel production is still premature at this point (my opinion only).

As a Moon hugger it is fascinating though. The more we explore the more interesting our nearest neighbour becomes (as is always the case with exploration).

Edit: I litre per 10 tons means processing a cube of regolith 2 meters-ish (regolith bulk density is around 1500kg /m^3 IIRC) on a side for 1 liter of water. If the water bearing regolith is easy to scoop up and process, then I might imagine a highly/fully automated 'slow accumulator' type process producing small amounts for niche applications (such as refuelling GEO satellites at intervals of years or more) But that's not just speculative, right now it's damn near sci-fi, which is the point I'm making.