Titan:Titan: AA FrozenFrozen LifelessLifeless WorldWorld oror anan AstrobiologicalAstrobiological Hotspot?Hotspot?

Jack Beauchamp Caltech

For details see jlb.caltech.edu and jpl.nasa.gov PlanningPlanning forfor postpost--Cassini/HuygensCassini/Huygens ExplorationExploration ofof TitanTitan A U of Arizona-Caltech-JPL Partnership

Pat Beauchamp, Jet Propulsion Laboratory

Jonathan I. Lunine, Lunar and Planetary Laboratory, U of A

Jack Beauchamp, Beckman Institute and Dept. of Chemistry, Caltech

Dennis Dougherty, Dept. of Chemistry, Caltech

Mark Smith, Department of Chemistry, U of A

Chris Welch, Merck and Co. Tell me before I blast you into orbit – do you have any evidence of life beneath your sun baked surface? MarsMars isis notnot anticipatedanticipated toto bebe anan organicorganic richrich environment!environment! TitanTitan isis anan organicorganic paradise….paradise…. CassiniCassini-- HuygensHuygens MissionMission toto SaturnSaturn

CassiniCassini OrbitalOrbital Insertion:Insertion: JulyJuly 1,1, 20042004 DecemberDecember 24,24, 20042004 Released Probe Huygens Released Probe Huygens TitanTitan LandingLanding JanuaryJanuary 14,14, 20052005 HuygensHuygens ProbeProbe InvestigationsInvestigations

• Aerosol Collector Pyrolyser (ACP) • Descent Imager and Spectral Radiometer (DISR) • Doppler Wind Experiment (DWE) • Gas Chromatograph and Mass Spectrometer (GCMS) • Huygens Atmospheric Structure Instrument (HASI) • Surface Science Package (SSP) Titan • A natural satellite of Saturn, discovered in 1655 by Dutch scientist Christiaan Huygens. • The second-largest moon in the solar system. • One of a triad of moons with bulk densities of 1.8 g/cm3, and radii ~ 2500 km (Ganymede, Callisto, and Titan) • Titan is distinguished by having a very dense nitrogen atmosphere—four times denser than Earth’s.

For the purpose of this talk Titan will be granted honorary status as a small planet. Pressure, bars Titan’s Atmosphere • Mostly molecular nitrogen atmosphere, with an admixture (2- 10%) of methane

• Temperatures are very low (95 K surface, 70 K at 50 km), so that methane condenses out in the troposphere.

• Methane in the stratosphere is broken apart by ultraviolet photons from the Sun;

makes C2 and higher hydrocarbons HuygensHuygens isis aa success!success!

Cassini Delivers Huygens Probe to Titan http://www.esa.int WhenWhen itit RainsRains onon Titan,Titan, itit PoursPours (Methane)!(Methane)! TitanTitan AtmosphereAtmosphere asas seenseen byby CassiniCassini

July 1, 2004 “T0”

A spectrum of Titan’s stratosphere from Cassini CIRS, with the products of methane photolysis labeled. BeyondBeyond CassiniCassini--Huygens:Huygens: TheThe AstrobiologicalAstrobiological PotentialPotential ofof TitanTitan

• Titan has a dense atmosphere that is marginally oxidizing • Methane and nitrogen: source materials of biological interest • Varied sources of energy: UV, particle, impacts, release of bond energy in surface polymerization of organic molecules • A solid surface on which organics are accessible • Large spatial and temporal scales • Presence of liquid water at particular times and in limited places LaboratoryLaboratory StudiesStudies ofof TheThe OrganicOrganic ChemistryChemistry ofof Titan:Titan: TheThe TitanTitan TholinTholin ProjectProject

• Simulated Titan Chemistry -electrical discharge and VUV • Spectroscopic characterization • Separation and analysis • Structural chemistry -general aspects of polymer structure -functional group analysis • Reactivity -introduction of oxygen SynthesizingSynthesizing andand AnalyzingAnalyzing TholinTholin AnalogsAnalogs

Small Tholin Generator - Air-free isolation in dry glove box - Tholin generated at 77K to 300K

Large Tholin Generator - Walls of reactor cooled - Large quantities of tholin Coolant produced

Gas Mix

Vac Pump

Tholins SynthesizingSynthesizing andand AnalyzingAnalyzing TholinTholin AnalogsAnalogs

Photochemical Tholin Generator • Effects on % fixed nitrogen • VUV photolysis at 118 or 140 nm and 104-200 nm via synchrotron radiation at ALS

QCM film thickness monitors

Sample deposition substrates window

ALS Beckman Institute External Ion Source FT-ICR Mass Spectrometer ESIESI FTFT--ICRICR StudiesStudies ofof TholinTholin CompositionComposition

Representative high resolution ESI FT-ICR spectrum of a 2%

CH4 in N2 tholin run. Simple and regular patterns are seen in the molecular weight distribution of the compounds in regularly spaced clusters

(General formulae of CxHyNz were obtained by accurate mass measurements) C6H11N4 139.0984 “ “ 139.1235 C Fresh” TholinSample Fresh” TholinSample 8 H 15 N 2

C5H10N5 140.0936

C7H14N3 140.1188

C6H13N4 141.1140 141.1392 C 8 H 17 N 2 Exposure toOxygen andWaterLeadsto Exposure toOxygen andWaterLeadsto

C5H7N4O 139.0620 Incorporation ofOxygen Incorporation ofOxygen C6H11N4 139.0984 139.1235 C

8 C H O 139.1123

H 9 5 15 N 2

C6H10N3O 140.0824

C5H10N5 140.0936

C7H14N3 140.1188

C5H9N4O 141.0776

C6H13N4 141.1140 C 141.1392 8 H 17 N 2 Fragmentation Studies Fragmentation Studies

-CH3CH=NH

-CH3CN -H C=NH CH3NH2 2 -HCN

-NH3 C C 7 9 H H -CH3 192 10 14 N N 7 5 Gas Chromatographic/Mass Spectrometry of Volatile Tholins and Tholin Hydrolysis Products

Nascent tholin: Solid phase extraction of volatile tholin vapors Hydrolyzed tholin: Volatile vapors (by solid phase extraction) resulting from 20 min (100 °C) aqueous hydrolysis of tholin solids

H N CN N H N NN NH NH NH2 NH2 NH2 NH NH H N NH2 N NNH2 NH HN HN N 2 N N H NH H N 2 N N NH H N N N H N N N

N N Hydrolyzed Tholin

H N O HO OH

NH2 O H N H O HN H O N

NH OH O N N O HN N OH N NH2 HO NH O O NH2 NH2 N H

OHO N N OH NH NH2 N

OH O

NH2 N

•Chiral compounds are observed in tholins and hydrolysis products •Free amines and imines are generally identified for the first time •Tholin contains many readily hydrolyzed functional groups •Compounds of biological relevance are ubiquitous Inference of an ethane-methane ocean on Titan TitanTitan isis anan OrganicOrganic ParadiseParadise Table of hydrocarbons and nitriles ½-1 km thick organic layer on deposited over 4.5 gyr (meters depth surface, mostly liquid averaged over the surface)

ethane 300-600 as liquid acetylene 100 as solid propane 20 as liquid hydrogen cyanide 20 as solid cyanoacetylene 2 as solid cyanogen 0.8 as solid carbon dioxide 0.02 as solid

There is no remote sensing evidence for such a “global” ocean (Lunine et al., 1983). Snapshots of of Cometary Impact with Velocity of 7 km/s and Impact Angle of 45◦

Three upper panels show the first second of an impact, when all the melt is produced under shock compression. The distribution of material is color-keyed: the atmosphere is yellow, both the surface ice and the comet are gray, and the molten material is green. Lower panel shows the situation at the end of the modeling: the transient cavity is not far from its maximum volume, but continues to grow at longer times because of Titan’s low gravity. Black arrow shows ejected surface material slowly falling into the melt layer inside the crater.

Impacts mix organic surface layers with subsurface ice and create astrobiological “hot spots” that persist for thousands of years at elevated temperatures. OrganicOrganic EvolutionEvolution onon TitanTitan Nitriles, hydrocarbons + liquid water Ø carboxylic acids Ø amino acids Titan has Ø • An organic-rich, redox-neutral enantio-enrichment environment Ø • Multiple sources of energy peptides • Long spatial and temporal scales Ø • Transient episodes of liquid water ????? ReturnReturn toto Titan:Titan: 20??20??

???? StereochemicalStereochemical specificityspecificity asas aa signpostsignpost ofof advancedadvanced organicorganic chemistrychemistry Serine Enantiomers

• A number of compelling arguments are made in the literature that the complex chemical systems required for life must be enantiomerically pure (a.k.a. homochiral). • Another stereochemical sign of the evolution of organic chemistry toward life might be preferred structural orientations in polymers, i.e. “tacticity”. • In general, a bias toward preferred isomers and a non-random molecular weight distribution would suggest evolution from abiotic organic chemistry toward biochemistry; enantiomeric and tactic selection would be a stronger indicator of that evolution. • Stereochemistry is the touchstone of our effort but not the entire scope—we are developing a general suite of analysis tools for planetary organics. Current Methods of Chiral Discrimination Chiroptical- polarimetry, circular dichroism Simple, general Poor sensitivity

NMR Complicated, requires specific derivatization or shift reagent, poor throughput

Chromatographic methods-LC, GC, etc Simple, general, sensitive Difficult to interpret complex, unknown mixtures

13. DL-Phenylalanine Determination of Enantiomeric Excess

Approach 1

Liquid/Gas Mass Sample Chromatography Spectrometer (Chiral Separation) (MSn)

Goal: Build a detector that responds only when there is an Approach 2 enantiomeric excess

Liquid/Gas Chiral Mass Sample Chromatography Detector Spectrometer (MSn) Piezoelectric Detection: Methodology

Quartz plate Electrode

Quartz Crystal Microbalance (QCM) Surface Acoustic Wave Detector (SAW)

The quartz crystal microbalance (QCM) is capable of measuring mass changes in the nanogram range. QCM’s are piezoelectric devices fabricated of a thin plate of quartz, with gold electrodes on each side. The addition of mass to the QCM leads to a change in its resonant frequency. A chemically selective film applied to the surface creates a chemical detector. The SAW detector operates by transmitting a surface wave from one end of the crystal to the other, through a chemically modified surface. Piezoelectric Detection: Monolayer Synthesis Self-assembled monolayers are used as the sensing layer to achieve a rapid response. The chiral selectors in these monolayers are also used in chromatography for chiral separation.

QCM Au electrode O O

Au Au S 15 OH + HS 15 OH MeOH, 2 hours

+

O H DCC, TEA N H N Au S 15 N DCM, 12 hours H O H2N O

L-valine t-butyl amide is coupled to a 16-mercaptohexadecanoic acid monolayer on the gold electrodes of a QCM. 1 0 Piezoelectric Detection:Methyl-(R)-Lactate QCM Data -1 Methyl-(R)-lactate -2 -3 z) -4 Exposure -51 FrequencyShi ft (H

Frequency Shift(Hz) -60 0 200 400 600 800 1000 1200 1400 -1 Time (s) -2 Methyl-(S)-lactate -3

z) -4 ift (H h S y c n e

u -5

q Exposure re F

Frequency Shift(Hz) -6 0 500 1000 1500 Response of a 15 MHz TimeQCM (s) exposed to methyl lactate vapor. Concentrations are 16, 32, 64, 128,and 256 ppm for each successive exposure. Piezoelectric Detection: Experimental

A dual crystal QCM (or SAW) is used, with the second, uncoated crystal used as a reference. The outputs of the two crystals are mixed, and the difference frequency is monitored. The crystals are set in a gas flow cell for introduction of the analyte. Computer

53131a Counter

Mixer

Oscillator Oscillator

N2 Precision Gas Analyte Diluter Vapor QCM PostPost--HuygensHuygens ExplorationExploration ofof Titan:Titan: TheThe SearchSearch forfor LifeLife onon OtherOther WorldsWorlds

TheThe MovieMovie