I’ve been sharing the mission and vision of Planetary Resources with many audiences lately – read about my talks at the University of Alberta or Seattle’s monthly Hacker News meet up.

My favorite part of the presentations are the questions! One that comes up a lot, is the possibility of obtaining precious metals from seawater being easier than asteroid mining.

Lets do some basic calculations to explore this:

The approximate concentration of Platinum in seawater is about 2.34E-10 grams per liter. That’s a 2 with 9 zeros before it, a very small number:

0.000000000234 grams per liter

On the other hand, lets consider how many liters of water there are in the ocean: 1.3E21 liters

That’s a 1 with 21 zeros after it, a very big number!

**1,300,000,000,000,000,000,000 liters**

Multiply this together, and we end up with approximately 300,000 tonnes of Platinum in the seawater. At today’s price for Platinum (about US$1600 per ounce), this is $16 Trillion, or a $16 million million. That is a *kingly* sum.

Sounds attractive, right? But now we need to process all the water in all the oceans, and it’s a big task. We’re going to need to pump a lot of water, so lets get a big pump.

How about something Niagra Falls-sized?

Flow rate of Niagra falls: 5.7E6 liters per second.

It would only take 7 million years to work through all the water on Earth (if we had a pump and processing plant that big). This will certainly introduce some other problems. So, lets be a little more reasonable and say we could process 1 millionth of the ocean (1.3E15 liters) in 7 years, with a processing plant with the flow rate of Niagra Falls (still quite a challenge).

We’d then have about 300 kg of Platinum, with a market value of around $16 Million.

Thankfully, in asteroids similar to LL chondrites and iron meteorites that have been studied here on Earth, the concentration of precious metals like Platinum is a BILLION times higher than the ocean.

Conclusion: While asteroid mining is a big task, its much more tractable than processing enormous amounts of seawater!

In a followup, we’ll talk about how the water on carbonaceous asteroids paves the way for a robust space economy!

Chris Lewicki

*President & Chief Asteroid Miner*