Astrobiology of Titan and early results from Cassini-HuygensOverviewPowerPoint PresentationFacts about Saturn (i)Facts about Saturn (ii)The Giant MoonObscured by cloudsAtmospheric CompositionEarth vs Titan AtmospheresTitan’s surfaceGot to have chemistry…The mystery deepens…Organics to pre-biotics?TholinsSlide 15Water on TitanLiquid assetsAstrobiology on Titan?A New Mission to SaturnCassini-HuygensSlide 21Cassini InstrumentsHuygens InstrumentsHuygens is prepared…Ready to go…Blast-off!Cassini takes the scenic route to Saturn…Going Into Orbit!A Grand DesignWhat has Cassini discovered so far?From a distance…Purple hazeFull MoonBeyond the visibleCIRS Infrared SpectrumThe missing atmosphere…Slide 37Through the haze..Land O lakes?Radar Mapping‘Cat-scratches’‘Circus Maximus’Xanadu SmileTitan Cryovolcano?Destination Titan!Mission TimelineTargeting TitanJigsaw PuzzleRiver to the shore?Splash or Bump?Titan ‘boulders’What have we learned?What is still unanswered?THE END…Astrobiology of Titan and early results from Cassini-HuygensLecture at Penn State Astrobiology Workshop for EducatorsJuly 28th 2005Dr Conor A NixonUniversity of Maryland/NASA GSFC/Cassini CIRS TeamOverview• Saturn system summary.• Titan - the enigmatic moon.• Why go back?• The Cassini-Huygens spacecraft.• Latest and greatest Cassini pictures and results.• Huygens landing.• Where do we go from here?Facts about Saturn (i)• Saturn is the 6th planet from the Sun, 9.5 times as far as the Earth.• Saturn is the 2nd largest by mass and radius.• Saturn is mostly composed of the same materials as the Sun: H2 and He.• Other common elements such as C, N, O, P are hydrogenated: CH4, H2O, PH3, NH3 etc.• Condensates such as NH3 ice form the visible cloud deck: there is no ‘surface’ like the Earth.Facts about Saturn (ii)• Saturn has the most extensive ring system of any planet in the solar system.• Saturn rotates with a period of 10 hours 40 minutes (interior) with an axial tilt of 26°.• Saturn has 2nd most moons (47, for now!), after Jupiter (63).• Saturn’s largest moon, Titan, is the 2nd largest in the solar system.The Giant Moon• Titan was the sixth moon ever to be discovered, in 1655 by Dutch astronomer Christian Huygens.• Named due to its massive size, Titan was originally thought to be the solar system’s largest moon.• Through a large telescope, Titan appears as a fuzzy pale orange ball. Even Voyager 1 saw little detail.Obscured by clouds• Titan’s size was originally over-estimated: we are looking at dense, thick layers of opaque haze, not the surface.• Voyager 1 snapshots of the planet’s edge (1980) showed that the haze was multi-layered.• Voyager 1 finally solved the question of size, by using radio waves to penetrate the haze. • Titan’s diameter of 5150 km is larger than Mercury, but smaller than Ganymede.Atmospheric Composition• In addition, the atmosphere contains several percent of methane, and many compounds of H,C,N: but no free O2.• We now know that the atmosphere is largely composed of nitrogen. Which other planet is like this?Earth vs Titan AtmospheresTitan’s surface• This artist’s impression shows lakes of liquid hydro-carbons (‘natural gas’), such as ethane on the surface of Titan - is this likely?Got to have chemistry…• Titan’s atmosphere is like one giant chemistry lab: UV light from the distant Sun splits up some of the native methane and nitrogen molecules.• The pieces of these molecules are then free to bond together in new ways, forming heavier chemicals which are expected to condense and rain out.• Over billions of years, huge lakes of liquid hydrocarbons should have accumulated on the surface, at least, that’s what we thought…The mystery deepens…• This image shows one of the best-ever pictures of Titan taken from the Earth (HST).• A huge bright, icy continent was spied on the leading side of Titan.• BUT - no dark lakes of liquid hydrocarbons.• What could be wrong with our theory?Organics to pre-biotics?• The presence of simple organic (‘carbon containing’) molecules on Titan led scientists to speculate whether any more complex, ‘pre-biotic’ molecules may have formed too.• Khare, Sagan and colleagues experimented by passing a DC current though a reaction vessel containing 90% N2 and 10% CH4 to simulate Titan’s atmosphere.Tholins• This experiment produced a tarry, reddish-brown goo which formed on the walls of the reaction vessel.• This was named ‘tholin’, after the Greek word for mud!• Tholins have been intensively studied in the lab as possible analogs for Titan and Triton hazes.• Khare et al also found that by the simple addition of HCl, 16 amino acids were produced.• What are amino acids and why are they so important?Amino Acids From Tholin• Amino acids are the building blocks of proteins, and essential to cellular life as we know it. They are sometimes called prebiological molecules.• Chemically, an amino acid is a carbon molecule which has three types of bonding other than simple C-H bonds: C=O, C-OH, and C-NH2.Water on Titan• Titan is much too cold for surface liquid water, with a temperature of 95 K (-178°C). • Life as we know it on Earth cannot survive without liquid water.• However, it has been proposed that water could exist temporarily in melt pools produced by impacts.• Large melt pools hundreds of meters deep might take centuries or even millenia (if mixed with ammonia) to freeze completely.Liquid assets• This is long enough for interesting organic chemistry to take place!• Chemical reactions in surface melts could add oxygen from water to the N, C, H in the tholin to make carboxylic acids, purines and pyramidines.• As well as the surface, Titan may well have a sub-surface ocean like Europa.• This is needed in many models to allow methane to escape from the interior, and replace the methane lost in the atmosphere by chemistry.Astrobiology on Titan?A New Mission to Saturn• The Voyager 1 and 2 missions which had flown by Saturn and Titan in 1980-1981 had raised almost as many questions as they had answered.– What is the surface like? Are there lakes or seas?– Why is Titan the only moon with an atmosphere?– Where does the methane go to/come from?– Is Titan similar to a prehistoric Earth?• A new mission was needed, one which wouldn’t just fly past while snapping a few shots, but go into orbit for years, examining