Titan’s smog clears a little

The atmosphere of Titan is of great interest as it is the only one in the solar system remotely like that of Earth, containing a nitrogen rich mix of gases.

 

Data collected using the Cassini Plasma Spectrometer and the UK-led sensor on it, the Electron Spectrometer, have revealed an unexpected cloud of very heavy ions 1000km above Titan's surface.

 

These ions are complex organic molecules formed from methane and nitrogen when exposed to intense sunlight, such as polycyclic aromatic hydrocarbons (PAHs) and similar compounds containing Nitrogen. They gradually form more and more complex molecules - reaching masses of 8000 times that of a single Hydrogen atom, possibly up to 40,000 times (more complex than insulin).

 

These molecules sink towards Titan's surface, forming a group of compounds named 'tholins' by Carl Sagan. Tholins were observed in the Urey-Miller experiment in 1953 which demonstrated that organic molecules could be formed from inorganic precursors. As such, they may provide the building blocks from which life forms.

 

Dr Andrew Coates from UCL's Mullard Space Science Laboratory, a co-author on the paper and lead of the ELS team, said "It's humbling to think that, with our instrument at Titan, we may be seeing processes which were at work in Earth's early atmosphere and which eventually led to life on Earth. It turns out that Titan's atmosphere is an organic chemical factory on a grand scale. To see such heavy negative ions was a big surprise for us, and is a key finding linking processes in Titan's atmosphere to the surface of Titan itself - and perhaps to dark, PAH-related deposits on Saturn's other moons."

 

"Tholins are very large, complex organic molecules thought to include chemical precursors to life," said Dr. Hunter Waite, from the Southwest Research Institute, and leader of Cassini's Ion Neutral Mass Spectrometer (INMS) team. "Understanding how they form could provide valuable insight into the origin of life in the solar system."

 

"The negative ions were a complete surprise," said Dr. David Young, also an SwRI Institute scientist, and leader of the CAPS investigation. "This suggests they may play an unexpected role in making tholins from carbon-nitrogen precursors."

 

UK participation in the Cassini mission is funded by the Science and Technology Facilities Council.

 

 

Images of Titan (link opens in a new window) |

 

Cassini-Huygens is a joint mission with NASA, ESA, and ASI, the Italian Space Agency. It was launched in 1997 to study Saturn and its rings and moons. ESA contributed the Huygens probe, which was released by the Cassini mothership in 2004. UK scientists have taken part in the development of eight of the eighteen instruments on Cassini and Huygens.

 

Julia Maddock

Science and Technology Facilities Council

Press Office

Tel +44 1793 442094

Julia.maddock@stfc.ac.uk |

 

Dr Andrew Coates (at a conference)

UCL MSSL

Mobile +44 7788 448318

ajc@mssl.ucl.ac.uk |