You may have heard of abiotic oil, the notion that oil is not the result of ancient biomass - hence the term fossil fuels - but rather from compressed methane seeping up from the Earth's mantle. Most petroleum engineers spurn abiotic oil as a crackpot idea, but the notion has percolated along and been popularized by books such as Thomas Gold's Deep Hot Biosphere. Setting aside the climate issue of burning petroleum, the idea of naturally replenished oil supplies is alluring considering oil is by far the most portable, energy dense fuel around. [A] paper published in Energy & Fuels, a peer-reviewed publication, supports the theory of abiotic oil. For their study geochemists at the Carnegie Institution of Washington combined the key ingredients for the abiotic synthesis of methane in a device and then simulated the high pressures and temperatures near the interface between the Earth's crust and mantle. They found it highly plausible that methane could form from chemical reaction in this environment, writing that their experiment "strongly suggests that it is likely that, in deep earth geologic systems, some methane generation is inevitable." The theory of abiotic oil holds that rapidly rising streams of compressed methane gas reach the crust from the mantle, and when they strike pockets of high temperature they condense into heavier hydrocarbons like crude oil.