Lunar Geothermal Energy: Is it Usable?

[dimensionless]

Are there sources of geothermal energy on the Moon? I imagine that there must be at least some nuclear decay that generates heat on the Moon. I don't know if any of it is sufficient for use as an energy source by humans.

 

[Vanadium 50]

No, the moon is geologically dead.

 

[LURCH]

Moonquakes have been recorded by instruments left on the surface by the Apollo missions. So there might be some geothermal energy, but the cause of moonquakes is not yet known. One theory is that the quakes are caused by landslides in crater walls, so that would mean no molten mantle.

Truth is, we really just don't know.

 

[Vanadium 50]

I'm going to disagree with Lurch - we're very sure the moon is geologically dead. We can quibble about "how dead is dead", but that's exactly what we are doing: quibbling.

There are moonquakes. Some are caused by tidal forces, some are caused by meteor impacts, and some are caused by thermal expansion and contraction of the lunar crust as it is alternately baked and frozen during the moon's long day and night. The type most like earthquakes are 28 events measured from 1969 to 1977 called "shallow moonquakes", which may be caused by (as Lurch said) by landslides in crater walls. These can register around a 5 on the Richter scale.

In any event, the rate of moonquakes is 28 over 8 years, or about 3.5 per year. In the last 365 days, the Earth saw 1637 earthquakes of that magnitude or higher. Put another way, looking at the 28 most energetic earthquakes in a similar period, the average energy is about 15,000 times larger on the earth.

So it's quite dead.

 

[LURCH]

I'd have to give you that one, Vanadium. Some of the literature I've read says that we don't really know the source of those quakes, but a second look at the facts makes it pretty clear that it isn't evidence of a molten mantle. Always been something of a mystery to me; how our siezmometers register quakes when there's no evidence of tectonic movement.

Ok, it's dead, Jim.

 

[dimensionless]

I don't thing thermal energy from radioactive decay would require a geologically active moon. Surely heavy elements exist in some quantity however small it might be. I guess what I was wondering was whether these heavy elements existed in densities sufficient to create warm spots...I'm not quite sure how the process works here on the Earth, and I'm not sure how it would work if the heat here was exclusively from radio active decay.

 

[Vanadium 50]

If there were a substantial source of heat internal to the moon, it would drive geological activity. Since no substantial geological activity is measured, we know there's not a lot of internal heat being generated.

 

[dimensionless]

If there were a substantial source of heat internal to the moon, it would drive geological activity. Since no substantial geological activity is measured, we know there's not a lot of internal heat being generated.

Couldn't I make the same claim about Mars, and conclude that the methane in the Martian atmosphere must have a biological origin?

 

[Vanadium 50]

Why? While Mars is probably nearing the end of it's geological activity, it's not known to be as dead as the moon, and there is some evidence of marsquakes.

 

[LURCH]

Perhaps more importantly; there is evidence of (relatively) recent vulcanism on Mars. The vulcanic cones are still standing. Some of the "rimless craters" on the moon are considered to be of vulcanic origin, but all of them appear to be very old.