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A comment on Earth as a nuclear furnace (geothermal heat is mostly from radioactive decay).

Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by hartror on Sunday April 03, 2011 @10:16PM (#2405023)
The beauty of this is geothermal heat adds the opportunity for life to develop/survive outside the Goldilocks Zone [1]. Not just in our solar system where the moons of Jupiter and Saturn are very active geologically due to tidal forces [2] but on extrasolar moons and planets that otherwise may not be suited to life.

Perhaps there is more life in the universe where the base energy source is that of geothermal than that of radiation from a star? I wonder what an sentient life form evolved from this environment would be like?

I feel a short story coming on.

[1] http://en.wikipedia.org/wiki/Habitable_zone

[2] http://en.wikipedia.org/wiki/Tidal_force

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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by turnersauce on Monday April 04, 2011 @01:39AM (#2405538)
It's funny that this is coming up now - just this week, there was a pre-print on arxiv.org that explored the possibility of a planet being heated (possibly enough to become habitable) by dark matter annihilation in its core: http://arxiv.org/abs/1103.5086
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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by ars on Monday April 04, 2011 @12:15AM (#2405354)
The long term stability of such a heat source is poor (it would start very hot, then cool exponentially). But it's an interesting idea.
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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by sliverstorm on Monday April 04, 2011 @02:20AM (#2405616)
You do realize that exponential decay actually translates to always-declining but relatively stable behavior as you approach the limit, right?
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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by jarin on Monday April 04, 2011 @01:31AM (#2405521)
How long is long term though? If I'm reading this right, the highest generator of heat is naturally radioactive thorium, which has a half-life of about 14 billion years. The Earth is only about 4.54 billion years old.
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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by ars on Monday April 04, 2011 @01:47AM (#2405555)
No, thorium is the lowest, not the highest. It decays too slowly to be a large source of heat.

Potassium-40 (1.2 billion years) is the highest.

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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by jarin on Monday April 04, 2011 @01:55AM (#2405571)
The article says that thorium releases 3.27×10^-12 Watts of heat per kg of mantle, while potassium releases 1.08×10^-12 Watts.

Isn't that more, or do I just fail at basic math?

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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by ars on Monday April 04, 2011 @02:40AM (#2405647)
I got my info from here: http://www.berkeley.edu/news/media/releases/2003/12/10_heat.... which said potassium. Shrug.
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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by sliverstorm on Monday April 04, 2011 @02:21AM (#2405617)
It would be interesting to determine how much of the dark side of the Earth is heated by leftover warmth from the daylight, and how much is geothermal.
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Re:Earth as a nuclear furnace (geothermal heat is mostly fro... by baddox on Monday April 04, 2011 @02:58AM (#2405682)
My guess is that geothermal contributes almost nothing. I wouldn't be surprised if the solar radiation via a full moon contributes more than geothermal.
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