Ten years, 590 flights (including 144 ocean crossings), 13, 110 passengers and more than a million miles later, the Graf retired, having set an enviable safety record.

FORBES: The long, loud history of hydrogen as a motor fuel.

According to the Bureau of Ocean Energy Management, Regulation and Enforcement, Gulf offshore natural gas production accounts for about 13% of overall U.S. natural gas supply.

FORBES: Damaging Hurricanes Could Impact Energy, Insurance Industries In 2012

Under the UN's Convention on the Law of the Sea, mining rights on the ocean floor are controlled by a little-known body, the International Seabed Authority, which since 2001 has issued 13 licences - with another six in prospect.

BBC: UK Seabed Resources joins deep-ocean mineral-mining rush