August 26, 2014 - Luckily for researchers, there is a possible laboratory in our solar system to help us better understand the conditions on Earth before life arose — a situation sometimes referred to as a “prebiotic” environment. That location is Titan, the largest moon of Saturn, that has fascinated researchers for decades, particularly after NASA’s Voyager 1 and Voyager 2 spacecraft flew by Saturn in the 1980s. The missions revealed a moon completely socked in with haze, which is a different experience to those used to gazing at Earth’s airless, cratered moon.
A recent finding revealed that Titan’s atmosphere is likely older than that of Saturn. This suggests that the moon did not arise from the ringed gas giant, but instead was created separately in the gas and dust floating around the young Solar System while the Sun and planets were being formed.
A closer look came in 2004, when the Cassini-Huygens mission arrived to study the system. Since then, the spacecraft has done hundreds of flybys of Titan and peered at its surface by penetrating the clouds with radar. The European Space Agency’s Huygens lander also made a soft landing on the moon in 2005.
One of the big research questions is the composition of the haze. A new study is trying to recreate substances in the atmosphere called tholins, organic aerosols which are produced when radiation bakes the nitrogen and methane-rich atmosphere. In some cases, organics are considered precursors to life.
“The study of organic chemistry on Titan’s surface would extend our understanding of the diversity of prebiotic chemistry, and perhaps life’s origin on Earth,” said Dr. Chao He, a chemist at the University of Houston (now moved to Johns Hopkins University) who led the study.
The results were publishedas “Solubility and stability investigation of Titan aerosol analogs: New insight from NMR analysis” in the journal Icarus.
According to He, the study of Titan’s tholins help scientists understand the basic properties of organic materials on Titan. Questions to consider include how they are structured, whether the aerosols can be dissolved in liquid in Titan’s surface or atmosphere, and how stable the organics could be. Titan’s tholins are thought to contain chemical precursors of life, and studying the molecule’s structure helps scientists better understand whether life’s possible precursors have formed on Titan. If they have formed, the solubility study helps to hint where to find them on Titan, and the stability study suggests the most capable detection methods.
The tholins were created by making a mix of methane (5 percent) and nitrogen (95 percent) in a reaction chamber at room temperature. The mixture was exposed to an electrical discharge for 72 hours, which then created a muddy substance — the tholin — on the walls of the vessel. The substances produced had a similar optical appearance to what Cassini observed in Titan’s atmosphere.
Researchers then investigated how well the tholins would dissolve in a solvent.