Experimental Studies to Determine the Impact of Propane and Acetylene on the Environment In and Around Titan's Lakes
The FINESST Fellowship has provided me with the opportunity to explore how certain minority species impact Titan's lake environment. Propane and acetylene are two of the most common hydrocarbon produced from the methane photochemisty occurring in Titan's atmosphere. These molecules may find their way to the lakes either but directly falling in or through indirect means via fluvial processes.
The goal of the study is to add varying quantities of propane to methane-ethane-nitrogen system—and later add acetylene to the methane-ethane-propane-nitrogen system—and utilize Raman spectroscopy to determine these minority species affect the phases and phase transitions of the ternary system. These experiments will ideally provide insight into the processes occurring on the surface and at shorelines of the lakes and seas.
Preliminary work included mapping the methane-ethane binary phase diagram at low temperatures and pressures and investigating the three solid phases of ethane that occur between 89 and 90 K—given Titan's surface temperature range of 89-95 K, it is interesting to think about what kind of impact these solid phases could have on the lake environment. [DOI].
Tuning DraGNS' Interpretations to Titan's Expected
As a Dragonfly Student and Early Career Investigator, I am working with Drs. Patrick Peplowski (JHU Applied Physics Lab) and Ann Parsons (NASA Goddard Space Flight Center) to establish benchmarks for models of various Titan surface environments and to build our intuition for the DraGNS (Dragonfly Gamma-ray and Neutron Spectrometer) response to the possible elemental combinations on Titan.
The Dragonfly mission marks the first time a gamma-ray and neutron spectrometer suite will be sent to a water-dominated world. Previously, this instrumentation had only been used to study terrestrial bodies, where the focus was on detecting heavier rock-forming elements and hydrogen (an indicator of the presence of H2O and OH). Given the marked difference between rocky and icy worlds, we have created Titan surface simulant samples and are performing a series of experiments with DraGNS-like instrumentation to get a glimpse into this unique environment before Dragonfly's arrival to the satellite in the mid-2030's.
For more information on this project, check out this year's LPSC abstract.
Monitoring the Effects of Methane on the Solid Phases of Ethane with Neutron Diffraction
As mentioned above, pure ethane is known to have three solid phases at conditions relevant to Titan's surface. Phase II has been somewhat elusive in its metastability when cooling and narrow temperature range of approximately 89.7-89.9 K. While forming phase II when cooling has still eluded us, we have seen evidence of it in the Raman spectra while warming and have gotten further confirmation through neutron diffraction.
Teaming up with Dr. Helen Maynard-Casely of the Australian Nuclear Science and Technology Organisation (ANSTO), we continued with the use of neutron diffraction (with the wonderfully named WOMBAT instrument) to study the effects that small quantities of methane may have on the solid phases of ethane. Our primary questions are: 1) Does the addition of methane alter the temperature at which the solid-solid transitions occur? 2) Do we see the presence of phase II in both cooling and warming sequences, or at all?
Results are still pending, so stay tuned!