For those worried about their "carbon footprint"

Scientists say that a type of rock found at or near the surface in the Mideast nation of Oman and other areas around the world could be harnessed to soak up huge quantities of globe-warming carbon dioxide.

Their studies show that the rock, known as peridotite, reacts naturally at surprisingly high rates with CO2 to form solid minerals—and that the process could be speeded a million times or more with simple drilling and injection methods. The study appears in this week's early edition of the Proceedings of the National Academy of Sciences.

Peridotite comprises most or all of the rock in the mantle, which undergirds earth's crust. It starts some 20 kilometers or more down, but occasionally pieces are exhumed when tectonic plates collide and push the mantle rock to the surface, as in Oman. Geologists already knew that once exposed to air, the rock can react quickly with CO2, forming a solid carbonate like limestone or marble...

Similarly large exposures of peridotite are known on the Pacific islands of Papua New Guinea and Caledonia, and along the coasts of Greece and the former Yugoslavia; smaller deposits occur in the western United States and many other places...