A well-documented asteroid is set to safely pass by Earth this Friday. But here's the fascinating fact — the asteroid is said to be worth close to $200 billion. Deep Space Industries, an ambitious consortium of billionaires that recently revealed plans to mine nearby space rocks, estimates 2012 DA14 may contain $65 billion in recoverable water and $130 billion in metals. Nothing to sneeze at. 

But the 150-foot-wide 2012 DA14 will zip by untouched, thanks to its "highly tilted" orbit relative to Earth, which Space.com says makes it too elusive to chase down. "While this week's visitor isn't going the right way for us to harvest it, there will be others that are, and we want to be ready when they arrive," Deep Space Industries chairman Rick Tumlinson said in a statement.

But is this hurtling mass of rock and ice — which we haven't even glimpsed up close yet since estimates are based solely on its brightness — really a potential gold mine worth nearly as much as, well, Google?

Nope. Not even close, says Tim Worstall at Forbes. "The value of any lump of rock is not the value of the metals trapped within it. It is the value of those trapped metals minus the cost of untrapping them."

That $195 billion value rests upon two assumptions. The first, that there are no costs associated with going up there and mining it. The second, they are assuming the value of those materials in space, not the value down here. And they are calculating that value by taking the price on Earth and then adding the cost of boosting it into space. [Forbes]

NASA estimates that a solar-powered spacecraft might be able to fetch a 500-ton, 23-foot-wide asteroid — considerably smaller than our friend zipping by this week — for somewhere in the ballpark of $2.6 billion. But it would presumably take several billion more to actually break the thing down into salvageable components.

Worstall brings up another good point: The technology to mine an asteroid simply isn't ready for primetime yet. Without any viable means to tear the thing apart, there's no way 2012 DA14 is worth $195 billion. "It's simply not possible," he concludes. "Thus the price of mining it is infinite. $195 billion minus infinity is less than nothing... At our current level of technology asteroids are dirt, not ore."