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Project Reports

• Task 3.1.1: Stimulated Pre-Biotic Reactions on Titan Surfaces

  The program at Georgia Tech. involves Dr. Claire Pirim (postdoctoral researcher) and Dr. Thomas Orlando (PI). It focuses on understanding the reactions occurring on Titan’s surface with an emphasis on determining whether mineral deposits from meteoritic impacts can catalyze the formation of more complex molecules possessing a prebiotic character.

  ROADMAP OBJECTIVES: 3.1 3.2

• Task 3.2: Longer Wavelength Photochemistry of Condensates and Aerosols in Titan’s Lower Atmosphere and on the Surface.

  This study focuses on the condensed phase photochemistry on Titan. In particular, we focus on understanding longer wavelength photochemistry of solid hydrocarbons to simulate photochemistry that could occur based on the UV penetration through the atmosphere and on the evolution of complex organic species in astrobiologically significant regions on Titan’s surface. Here we investigate the oxygenation chemistry involving the condensed Titan’s organic aerosols with water-ice on Titan’s surface – induced by high energy photons simulating the cosmic ray induced chemistry on Titan’s surface.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2 3.3

• Task 3.4.2: Development of Direct Sampling Methodology for Analysis of Complex Organic Mixtures on Titan’s Surface

  Photochemistry in Titan’s dense atmosphere generates a complex mixture of organic molecules that have been deposited on Titan’s surface over time. Requiring no sample pretreatment or handling, the technique of direct analysis in real time (DART), combined with an ion trap mass spectrometer having 2 dimensional mass spectroscpy capability, is shown to be an enabling experimental methodology to vaporize, ionize, and structurally characterize organic components of this mixture.

  ROADMAP OBJECTIVES: None Selected

• Task 2.2.1: Characterization of Aerosol Nucleation & Growth on Titan

  The scientific goal of this task is to elucidate the mechanisms and develop a quantitative understanding of particle formation and growth in the Titan atmosphere.

  ROADMAP OBJECTIVES: 3.1

• Task 2.1.1.1: Titan Photochemical Model

  To develop a comprehensive model of the chemistry in Titan’s atmosphere including condensation of molecules onto grains, and sublimation back to the gas.

  ROADMAP OBJECTIVES: 2.2 3.1

• Task 1.1.1: Leaching of Radiogenic Potassium From Titan’s Core Into Its Ocean

  Working with graduate student Jason Hofgartner and NAI collaborator Christophe Sotin, we modeled the equilibrium chemistry of potassium at high pressure in the interior aqueous media in Saturn’s moon Titan to determine the extent of potassium leaching. This, in turn, allows us to test the hydrated silicate core model proposed by J. Castillo-Rogez and NAI Titan deputy PI Jonathan Lunine.

  ROADMAP OBJECTIVES: 1.1 2.1 2.2 3.2 7.1

• Task 2.1.1.2: Titan Photochemistry

  The Caltech effort has focused on the chemistry of hydrocarbons in the atmosphere of Titan and its relation to aerosols. We have an effort for analyzing the stellar occultation data from Cassini/UVIS instrument. The mean optical depth as a function of line of sight impact parameter is derived for the spectral range between 1700 and 1900 Å from stellar occultations.

  ROADMAP OBJECTIVES: 2.2 3.1

• Task 2.1.2.1: Titan General Circulation Model

  The goal of this effort is to produce realistic Titan atmospheric profiles [winds, temperatures and densities] from the surface to ~1200km, for a variety of seasons and solar cycles, for use by members of the overall Titan NAI project.

  ROADMAP OBJECTIVES: 2.2

• Task 2.1.2.2: Shortwave Solar Flux at Titan’s Surface

  What can we learn about pre-biotic chemistry by studying Titan? The surface of Titan is a special place for the study of pre-biotic chemistry because that is where the organic haze sedimenting from the atmosphere can come in contact with liquid water (briefly, from cryovolcanic eruptions) to form amino acids and other molecules relevant to life. But an energy source is also needed, and this may come from short-wave (ultraviolet – blue) solar radiation that makes its way through Titan’s dense haze layer to the surface. In this study we calculated the amount of UV-blue solar flux at Titan’s surface based on measurements made by the Descent Imager/Spectral Radiometer (DISR) instrument on the Huygens Probe coupled with radiative transfer models that include haze optical properties.

  ROADMAP OBJECTIVES: 2.2 3.1 3.2 3.3

• Task 3.3.1: Solubility of Organics in Simulated Titan Lake Solutions

  Widespread lakes of liquid methane and ethane were discovered on Titan by the Cassini mission in 2006, which naturally motivates questions about the solubility of surface materials in the liquid. Our goal is to measure the solubilities of Titan surface and atmospheric species in cryogenic liquid hydrocarbons, in order to constrain the composition of the hydrocarbon lakes, and provide an understanding into the nature of erosion and sedimentation on Titan. To date, we have measured the solubilities of argon and krypton in liquid methane and ethane, and the solubilities of benzene, naphthalene, and biphenyl in liquid ethane. Relatively high organic solubilities suggest that liquid hydrocarbon based weathering and sorting of surface organics should be occurring on Titan.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2

• Task 3.3.2: Trapping of Methane and Ethane in Titan Surface Materials

  We demonstrate that solid benzene can trap significant amounts of ethane and methane within its crystal structure at Titan surface temperatures. Experiments also suggest that liquid ethane can diffuse into solid benzene, resulting in the formation of a co-crystalline structure. This implies that lake edges and evaporite basins on Titan may hold important quantities of ethane. These results can help explain the release of methane observed at the Huygens landing site, and point toward a large possible reservoir of methane and ethane hidden within Titan’s surface organics.

  ROADMAP OBJECTIVES: 1.1 2.2 3.1 3.2

• Task 3.4.1: Nuclear Magnetic Resonance Spectroscopy Studies of Titan Organic Analogues: Analytical Potential

  Nuclear magnetic resonance spectroscopy (NMR) has tremendous potential for the quantitative identification of solar system organic molecules of simple to complex nature with absolute structural identification. We have investigated its potential for the elucidation of very complex mixtures of Titan aerosol haze analogues (Tholins) with identification of the major components of modest complexity using 1, 2 and 3 dimensional spectral techniques. We have also performed studies of the utility of low resolution NMR on low temperature liquid hydrocarbon mixtures analogous to Titan lake liquids towards the development of multidimensional NMR instrumentation capable of future flight missions to solar system bodies of organic composition.

  ROADMAP OBJECTIVES: 2.2 3.1 3.2

• Task 3.5.1: Titan as a Prebiotic Chemical System

  Six years ago, NASA sponsored a National Academies report that asked whether life might exist in environments outside of the traditional habitable zone, where “weird” genetic molecules, metabolic processes, and bio‐structures might avoid the water‐based biochemistry that is found across the terran biosphere. In pursuit of this “big picture” question, we turned to Titan, which has exotic solvents both on its surface (methane‐hydrocarbon) and sub‐surface (perhaps super‐cooled ammonia‐rich water). This work sought genetic molecules that might support Darwinian evolution in both environments, including non‐ionic polyether molecules in the first and biopolymers linked by exotic oxyanions (such as phosphite, arsenate, arsenite, germanate) in the second. Further, we asked about the possibility that Titan might inform our understanding of prebiotic chemical processes, including those on “warm Titans”. Our experimental activities found few possibilities for non‐phosphate-based genetics in subsurface aqueous environments, even if they are rich in ammonia at very low temperatures. Further, we showed that polyethers are insufficiently soluble in hydrocarbons at very low temperatures, such as the 90‐100 K found on Titan’s surface. However, we did show that “warm Titans” could exploit propane as a biosolvent for certain of these “weird” alternative genetic biopolymers; propane has a huge liquid range (far larger than water). Further, we integrated this work with other work that allows reduced molecules to appear as precursors for more standard genetic biomolecules, especially through interaction with various mineral species.

  ROADMAP OBJECTIVES: 1.1 1.2 2.2 3.1 3.2 4.1 4.2 5.3 6.2 7.1 7.2

• Task 3.6.1: A New Titan Chamber for Advancing Technology

  The objective of this project is to develop a cryogenic chamber capable of simulating Titan’s lake conditions (1.5 bar N2 atmosphere, liquid mixtures of methane-ethane-propane in variable concentrations), and provide an experimental volume of 10 L. The purpose of this facility is to provide an environment for testing components and small instruments. Such a facility currently does not exist but is needed for achieving Technology Readiness Levels of 5/6. It will also be available to the community for scientific investigations such as measuring the equilibrium composition of lakes under realistic conditions, and exchanges between lakes and atmosphere.

  ROADMAP OBJECTIVES: 2.2