Scientists probe the source of key hydrocarbons on Earth—and in space

Polycyclic aromatic hydrocarbons (PAHs) are a type of organic molecule that carry fused rings made of the chemical benzene. Scientists believe that PAHs are responsible for chemical processes that eventually lead to soot and other carbonaceous nanoparticles on Earth and around and between the stars in deep space. On Earth, PAHs form in part because of the incomplete combustion of coal, oil, and other substances and are detrimental to human health.