April 3, 2013
Complex Chemistry Could Lead To Life On Titan
Lee Rannals for redOrbit.com — Your Universe Online
Scientists reported in the journal Nature Communications that complex organic chemistry could eventually lead to the building blocks of life on Saturn's moon Titan.
Experiments at NASA's Jet Propulsion Laboratory have shown the same kind of biological chemistry on Earth's surface could also drive chemistry on Titan, even though the Saturn moon receives far less light from the sun and is much colder.
"Titan is not a sleeping giant in the lower atmosphere, but at least half awake in its chemical activity," said Murthy Gudipati, the paper's lead author at JPL.
Scientists have known Titan, Saturn's largest moon, has a thick, hazy atmosphere with hydrocarbons that include methane and ethane. These organic molecules are able to develop into smog-like, airborne molecules with carbon-nitrogen-hydrogen bonds.
"We've known that Titan's upper atmosphere is hospitable to the formation of complex organic molecules," said co-author Mark Allen, principal investigator of the JPL Titan team that is a part of the NASA Astrobiology Institute, headquartered at Ames Research Center in Moffett Field, California. "Now we know that sunlight in the Titan lower atmosphere can kick-start more complex organic chemistry in liquids and solids rather than just in gases."
The team looked into the ice from of dicyanoacetylene, which is a molecule that was detected on Titan that is related to a compound that turned brown after being exposed to ambient light 40 years ago. NASA researchers exposed dicyanoacetylene to laser light at wavelengths as long as 355 nanometers. This wavelength is able to filter down to Titan's lower atmosphere at a modest intensity similarly to how light comes through protective glasses when viewing a solar eclipse.
After performing this new experiment, researchers found the formation of a brownish haze between the two panes of glass containing the experiment. This confirmed organic-ice photochemistry at conditions like Titan's lower atmosphere could produce tholins.
These organics could be coating the "rocks" of water ice at Titan's surface and could possibly seep through the crust. Previous experiments showed tholins like these were exposed to liquid water over time, and developed into biologically significant molecules.
"These results suggest that the volume of Titan's atmosphere involved in the production of more complex organic chemicals is much larger than previously believed," said Edward Goolish, acting director of NASA's Astrobiology Institute. "This new information makes Titan an even more interesting environment for astrobiological study."
An international group of scientists are also looking into the reddish-brown smog that begins to appear on Titan in the ionosphere. A study published in Proceedings of the National Academy of Sciences back in February found this smog creates negative and positive ions that grow into large and more complex aerosols. As these ions bump into each other, they interact with other neutral particles, creating hydrocarbon rain on Titan's surface.