How Much is a Planet Worth?

Gliese 581 c: $160
Mars: $14,000
Earth: $Lotsa!

From BoingBoing:

Our planet's value emerged as nearly 5 quadrillion dollars. That's about 100 times Earth's yearly GDP, and perhaps, Laughlin thought, not a bad ballpark estimate for the total economic value of our world and the technological civilization it supports.

I find this kind of amazing, that one can simply plug in numbers regarding physical characteristics of a planet- quantities that don't, on the face of it, seem to have much to do with economic value- and get something that seems like a plausible estimation of the "worth" of the planet. $14,000 seems like a low value for Mars, to me, but I suspect that's at least in part because I think about its potential future value, not its value in terms of today's ability to utilize it.

The interview portion of the article goes into some detail of how the equation was pieced together, and helps clarify how this works. Still wondering about magnets and tides, though.