The Cassini spacecraft has flown through the upper atmosphere of Saturn's giant moon, Titan, and detected a huge number of complex organic chemicals. Scientists believe that similar processes may have built organic molecules in the atmosphere of early Earth.
Cassini’s closest encounter with Titan so far came on 16 April, as it skimmed within about 1000 kilometres of the moon's surface. During the flyby, an instrument called the Ion and Neutral Mass Spectrometer captured and analysed gases from the upper atmosphere. INMS uses a beam of electrons to ionise these gases before subjecting them to electric fields to measure the telltale atomic mass of different molecules.
Some complex organic molecules - such as benzene and diacetylene - had already been picked up on an earlier approach to Titan, but the latest encounter has yielded an even wider range.
It includes nitriles and scores of different hydrocarbons, some with up to seven carbon atoms. And the results suggest that Titan's upper atmosphere holds even heavier and more complex organics, which are beyond the instrument's mass range.
The INMS team were not expecting to find such a rich soup of chemicals so high up - it is something of a mystery why these heavy molecules do not rapidly condense in Titan's cold atmosphere and rain down to the surface.
Scientists do have some idea about how they are formed, however. Methane and molecular nitrogen are thought to be smashed apart by ultraviolet radiation from the Sun and by high energy particles trapped in Saturn's magnetic field. That creates highly reactive radicals that can combine to form more complex molecules.
Similar processes might have operated on the Earth a few hundred million years after it formed, generating the raw materials for life. On the other hand, Earth's organics may have been created in deep space and then delivered by comets.
The Huygens probe - which landed on Titan in January after hitching a ride with Cassini - had previously taken gas readings as it plummeted through the atmosphere, but only began those measurements as it fell beyond an altitude of 150 km.
The Cassini team are hoping to learn more about Titan's atmosphere over the next few years - at least 39 further flybys are planned.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
