Titan molecular minerals: The role of hydrogen cyanide
Abstract
Titan, the largest moon of Saturn, is considered a prebiotic chemical laboratory on a planetary scale. Photochemistry in the atmosphere induced by solar radiation and energy from Saturn's magnetosphere causes a chemical cascade, as N _{2} and CH _{4} dissociate and generate organic molecules ranging from simple (ethane, acetylene, HCN) to complex (>10,000 Da). Most of these molecules are transported down to the surface, where they may react and interact as they become integrated into the unique geology of Titan. We have demonstrated in previous work that two common organic molecules on Titan, ethane and benzene, form a stable co-crystalline structure at Titan surface temperatures. This co-crystal represents an exciting new class of compounds for Titan's surface, which would fill the role equivalent to a hydrated mineral in this environment.The discovery of one Titan organic mineral has led us to search for others. We have recently characterized several possible minerals incorporating acetylene, one of the primary solid photochemical products generated in Titan's atmosphere. These co-crystals - the acetylene series - form spontaneously and are stable under Titan surface conditions. The acetylene-ammonia co-crystal, for example, is robust against exposure to pluvial (rain) events of methane, ethane or propane.We are now investigating the HCN series. Hydrogen cyanide (HCN) may be even more abundant than acetylene on the surface of Titan. Preliminary evidence indicates that HCN associates with ethane and acetylene at 90 K, although the red and blue shifts observed in the Raman (up to 6 cm ^{-1}) are not quite as large as the shifts observed for the other co-crystal series involving benzene (up to 12 cm ^{-1}) and acetylene (up to 66 cm ^{-1}). This may be due to weaker associations between the species. We are exploring interactions of HCN with other hydrocarbons to better elucidate this relationship.
- Publication:
-
42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E.486C