The presence of life on Earth is tied in multiple ways to the presence of one substance — water. Water is the biggest component in most living organisms and has the power to leave a long-lasting impact on the environment. It is no surprise, then, that astrobiologists have long focused on understanding how exoplanets could develop the right conditions for life.
What happens when dynamic cycles of activity are present without water? That is the question that first arose in the mind of one Cornell scientist. Prof. Jonathan Lunine, astronomy, director for the Cornell center for astrophysics and planetary science, pondered the possibility of something unique happening on Saturn’s moon, Titan. Located 1.43 billion kilometers away from the Sun and with a surface temperature of 94 K (a few degrees above where methane freezes), the second biggest moon in the solar system is surprisingly active. Much like Earth, Titan is teeming with rivers and oceans which are constantly being replenished by rain. However, these rivers and rain are not water, but dynamic cycles of methane and other hydrocarbons. Lunine sought to understand if these cycles of methane could have a similar impact on Titan, in the way water has an impact on Earth.
This broad question would end up bringing together Lunine, Prof. David Shalloway, molecular biology and genetics, Prof. David Usher, chemistry and chemical biology, and Martin Rahm, theoretical and computational chemistry.
A molecular and computational biologist by training, Shalloway was in a position to provide insights into how chemically dynamic Titan was. The first indication that chemical reactivity was present on Titan was the lack of hydrogen cyanide on the surface in comparison to the atmosphere. According to the team, such an absence was thought to be the result of chemical reactivity leading to the formation of more complex molecules out of hydrogen cyanide. If hydrogen cyanide was reacting with itself, what kind of complex structures could develop?
This query lead Shalloway to ask more fundamental questions.
“Can you have life without water?” he pondered.
He observed that hydrogen cyanide, though poisonous on earth, behaves differently on Titan. Under the right conditions and assumptions, it was possible to imagine hydrogen cyanide molecules linking to one another — forming structures known as polyimines. When further assembled, polyimines could theoretically create structured layers capable of absorbing sunlight.
Rahm, a postdoctoral researcher in quantum chemistry, worked on understanding the theory behind this behavior and did the bulk of computational modeling.
“There is a tremendous lack of knowledge when it comes to this place [Titan]”, Rahm said
Describing the moon as a “natural laboratory”, Rahm first became interested in Titan after attending a workshop at the California Institute of Technology. After meeting with Lunine, he began working to come up with computational methods for studying chemistry on Titan. This past summer, his work resulted in a lead author publication in the Proceedings of the National Academy of Sciences.
Speaking about his fascination with chemistry he said it has the potential to uncover mysteries.
“Chemistry [can be] applied to study other worlds, [explore] the possibility of prebiotic chemistry and ultimately the origin of life,” Rahm said. “That might be one of the more important takeaways [of this research] in the inspirational use.”
This sentiment was echoed by Shalloway.
“Beautiful things are worth doing” he said.
While he certainly hopes that new explorations may uncover new findings on Titan and other worlds, Shalloway’s final observation perhaps most perfectly summarized the ultimate goal for his research.
“[Research and discovery] help us to be more humble,” he said.
A previous version of this article incorrectly stated that Titan had a surface temperature of 94 K (not far from that of liquid nitrogen). In fact, this temperature is closer to the freezing point of methane.
A previous version of this article incorrectly stated that Rahm was a “self -described quantum chemist.” In fact, he is a postdoctoral researcher in quantum chemistry.