Titan Home to Life's Building Blocks

Nov. 30, 2007 -- Scientists don't know how it happened, but the oxygen-starved atmosphere of Saturn's moon Titan contains chemicals that on Earth can serve as building blocks for complex organic molecules.

Using an instrument on the Saturn-orbiting Cassini spacecraft, scientists found heavy negatively charged ions in Titan's upper atmosphere, despite the absence of oxygen. On Earth, oxygen is needed to ionize molecules in the lower ionosphere.

Titan's atmosphere is mostly nitrogen and methane, a combination that is leaving scientists wondering how the negative ions, which have 10,000 times the mass of hydrogen, formed. Cassini collected the data during 16 different encounters of Titan.

"Their existence poses questions about the processes involved in atmospheric chemistry and aerosol formation," said Andrew Coates, with University College London's Mullard Space Science Laboratory.

With additional rings of carbon, the molecules can become what are called polycyclic aromatic hydrocarbons, which scientists believe can serve as a starting point for simple microbial life.