Since the end of the Apollo program, and the analysis of all the samples returned from those expeditions, the orthodox view of the moon has been one of dreary, dusty, homogeneity. Oh, there were things like Mascons, and your occasional magnetic anomaly to spicen things up somewhat, but the Moon was thought to be for the most part bone dry, boring, and overall pretty much the same wherever you went (with only minor difference for highlands vs. maria). Over the last several years, new data and new theories are starting to question that orthodoxy, painting the picture of a Moon that is potentially far more interesting than had been previously thought–both scientifically and economically.
Lunar Polar Deposits
The first major crack in the orthodox view of the moon came with the detection by both the Lunar Prospector and Clementine orbiters of potential hydrogen concentrations in the lunar polar regions. It had long been speculated by some scientists that the polar regions could possibly serve as a “cold-trap” that could keep volatiles from escaping back into space, however here was some hard evidence that that might very well be the case. Now this data is not without controversy. Recent data from the Arecibo radio telescope try to call the original data into question, however there are possible good explanations for that contradictory evidence, and the idea of lunar polar concentrations of volatiles has gains considerable traction recently. We don’t know a whole lot (yet) about the form of these volatiles (it could be water ice, hydrogen molecules trapped by the regolith, or maybe something else entirely), and are not entirely sure of their origin (cometary impacts, solar wind implantation, etc), but the general scientific consensus appears to support the idea that there is at least something interesting going on.
Another recent attempt at challenging the orthodox view of the moon has come from research done by a good friend of mine, Dennis Wingo. In his book, Moonrush, Wingo makes the case based on recent research for the possibility of intact platinum-group-metal-bearing nickel-iron meteorite impacts on the moon. Wingo’s case was based on models that predict the impact velocity distribution of objects striking the moon, computer models that predict the effect of impacts on the impacting body, and data on the number and distribution of Ni-Fe asteroids in the solar system and impact craters on the Moon. If he’s right, there’s a very strong possibility that there are economically interesting concentrations of nickel, iron, and platinum group metals on the moon.
Now, while the idea of lunar polar volatiles has gained considerable respect within the scientific community, Wingo’s hypothesis hasn’t gained anywhere near as much traction yet. As Wendell Mendell likes reminding Dennis at various conferences, there’s very little evidence from the Apollo lunar samples of his hypothesis. Fortunately, Dennis provided several methods in his book for trying to falsify his hypothesis.
Transient Lunar Phenomena
The most recent challenge to the homogeneous Moon orthodoxy comes in the form of some papers recently published in the journal Icarus regarding Transient Lunar Phenomena. A much simplified overview was provided by Space.com. The work, carried out by Crotts and Hummel of Columbia University in New York, is a rather fascinating read (though very, very complicated–I’m not sure I understood more than 25% of the details). Their main conclusions were that there’s good reason to believe that TLPs are real, they appear to be strongly correlated with specific geographic regions, and they appear strongly correlated to lunar outgassing. This outgassing might possibly lead to discoveries of gas pockets below the lunar surface in several locations, which depending on their makeup could be extremely useful for future lunar development. On a substantially more controversial note, Paper II by Crotts and Hummels postulates a mechanism that could lead to substantial subsurface ice deposits in the regions where TLPs are occurring (particularly in the region of Aristarchus crater). While these ice deposits would have been small enough that the resolution of previous neutron spectrometers and such might very well have missed them, this hypothesis is a long way from proven. If the existence of substantial subsurface gas and ice deposits do prove out though, it could have some very important scientific and economic ramifications. Crotts discusses some methods that they are currently using and some future methods for trying to validate or falsify their hypotheses, including using automated telescopes with computer algorithms watching for TLP events. The hope is that by detecting an event early, additional telescopes and sensors can be brought to bear, possibly providing a lot more useful information about what is going on. With several orbiters planned for the near future, the potential for getting close-up data on these events is even more intriguing. It should be a fun topic to watch.
While many of these hypotheses still have a long way to go before they’ve been proven out, it’s interesting to see that the orthodox view of the moon as being boring from both a scientific and economic perspective begin to change. We’ve got a long way to go yet, and some of these ideas might not pan out, or might end up not being as economically interesting as hoped. However, it’s really starting to look like the Moon may very well be a far more interesting place than anyone imagined.
[Note: this post is part of the 14th weekly Carnival of Space being held at Universe Today. Check out some of the other posts if you have the time]