A team of researchers from Cornell University in Ithaca, NY, has uncovered a chemical trail that suggests prebiotic conditions may exist on the surface of Saturn’s largest moon, Titan.
This composite image shows an infrared view of Titan. In this image blue represents wavelengths centered at 1.3 microns, green represents 2.0 microns, and red represents 5.0 microns. A view at visible wavelengths would show only Titan’s hazy atmosphere; the near-infrared wavelengths in this image allow Cassini’s vision to penetrate the haze and reveal the moon’s surface. The view looks toward terrain that is mostly on the Saturn-facing hemisphere of Titan. Image credit: NASA / JPL-Caltech / Space Science Institute.
Titan is a carbon-rich, oxygen-poor world with a wide range of organic compounds, atmospheric energy sources, and liquid hydrocarbon seas.
It is the only planetary body in the Solar System, except our planet, where rainfall and seasonally flowing liquids erode the landscape.
Whereas the surface pressure is similar to that of Earth, the temperature is extremely low and the dominant liquids are methane and ethane.
This makes Titan a test case for exploring the environmental limits of prebiotic chemistry and addressing the question of whether life can develop without water.
“To grasp the blueprint of early planetary life, we must think outside of green-blue, Earth-based biology,” said team member Dr. Martin Rahm, from Cornell’s Department of Chemistry and Chemical Biology.
“We are used to our own conditions here on Earth. Our scientific experience is at room temperature and ambient conditions.”
“Titan is a completely different beast,” he said.
When sunlight hits Titan’s exotic atmosphere, the reaction produces hydrogen cyanide (HCN), an organic chemical that can react with itself or with other molecules – forming long chains, or polymers, one of which is called polyimine.
Polyimine is flexible, which helps mobility under very cold conditions, and it can absorb the Sun’s energy and become a possible catalyst for life.
“Polyimine can exist as different structures, and they may be able to accomplish remarkable things at low temperatures, especially under Titan’s conditions,” said Dr. Rahm, first author of a paper published in the Proceedings of the National Academy of Sciences this week.
“We need to continue to examine this, to understand how the chemistry evolves over time. We see this as a preparation for further exploration.”
“If future observations could show there is prebiotic chemistry in a place like Titan, it would be a major breakthrough.”
“This paper is indicating that prerequisites for processes leading to a different kind of life could exist on Titan, but this only the first step.”
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Martin Rahm et al. Polymorphism and electronic structure of polyimine and its potential significance for prebiotic chemistry on Titan. PNAS, published online July 5, 2016; doi: 10.1073/pnas.1606634113
