1. Jorge Hernández Arce Física del Sistema Solar Master en Astrofísica UCM-UAM TheAtmosphere of Titan

2. Content • A littlehistory • Characteristics of themoon’satmosphere • General properties. • Composition. • SimilaritieswithEarth’satmosphere and theirmeaning. • Cassini and Huygens • References

3. A littlehistory • Firstsuspicions of anatmosphere Comas i Solá (1903). • ConfirmedbyKuiper in 1944. • Firstdetailedimages of themoonobtainedbyVoyager 1 in 1981 discoveringthattheatmospherewas, in fact, denserthantheEarth’s. • Already in the 21st CenturytheprobeHuygens, part of thespacecraftCassini, succesfulylanded in themoon’ssurface.

4. Characteristics of themoon’satmosphere • As aforementioned, it’sactuallydenserthantheEarth. Thesurfacepressureisabout 1.47 times greater. • Giventhisdensity, and thelowgravitationalforce of thesatellite (1.35 m/s2), theatmosphereismuch more extentthanours, itseffectsbeingappreciableeven at 1000 km of altitude.

5. Characteristics of themoon’satmosphere • Themain gases thatcomposeTitan’satmosphere are: • Nitrogen (98.4 %) • Methane (1.4%) • Hydrogen (0.1-0.2%) • Trace amountsof ethane, diacetylene, methylacetylene and otherhydrocarbons. • Also traces of other gases such as cyanoacetylene, hydrogencyanide, carbondioxide, etc.

6. Characteristics of themoon’satmosphere Hereistheatmosphericcomposition at different altitudes:

7. SimilaritiestoEarth’satmosphere • Themainsimilarityistheatmosphere’sdensityand composition. It’sroughly as dense as Earth (just a littledenser) and shares thesamemajorcomponent (nitrogen). • Thereisevidence of rain onthesurface of theplanet, althoughitdoesn’t rain water, butmethane. • Thereis a highamount of organiccompounds in theatmosphere, as aforementioned. • In high latitudes there are lakes of liquidmethane, whereasneartheequatorTitanis more arid, althoughthere are signs of thepresence of liquids.

8. SimilaritiestoEarth’satmosphere • Allthesesimilarities, speciallytheorganiccompounds, lead tobelievethatTitanisthemost probable candidatetoaccomodatelifeoutside of Earth, althoughitisstillhighly improbable duetootherconditions ( thesurfacetemperatureis 92 K in average). • Thepresence of liquidmethaneensuresthelack of oxygengiventhefactthatitwould cause themethanetoburn.

9. Cassini-Huygens • Itis a jointproject of NASA, ESA and ASI (ItalianSpaceAgency). • Launchedon 15th of October 1997 and arrivedtoSaturnthe 1st of July, 2004. • ThepartspecificallydesignedtostudyTitanistheHuygensprobe, whichseparatedfromthemainspacecraftthe 25th of December 2004 and landed in thesatellite’ssurfaceonthe 14th of January of thenextyear, 2005.

10. Cassini-Huygens • The Huygens probe is equiped with the following instruments: • Aerosol collector an Pyrolyser (ACP) • Descent Imager/Spectral Radiometer (DISR) • Doppler Wind Experiment (DWE) • Gas Chromatograph and Mass Spectrometer (GCMS) • Huygens Atmosphere Structure Instrument (HASI) • Surface Science Package (SSP)

11. Cassini-Huygens • Theprobe’smostimportantfindins are: • Theaforementionedmethanecycle. There are lakes of liquidmethane, fedby rain of thissamemoleculetogetherwithorganicones. • Winds in thedirection of rotation of themoon, between 60 and 100 km/h. • Solidsurface of Titanisorange, and spongy, can becomparedwith yogurt. • Possibility of a pastvolcanicactivitywith ice anammoniainstead of lava. • Thesurfacetemperatureisaround 90K.

12. References • Biemann, H. B., Atreya, S. K. et al. 2010 Journal of GeophysicalResearch. V. 115. • Turtle, E. P., Perry, J. E., et al. Science V. 331 2011 • Yung, Y. L., Allen, M. et al. TheAstrophysicalJournalSupplement Series, 55:465-506, 1984. • Rodriguez, S.; Le Mouélic, S. et al. Nature 459 2009. • http://www.esa.int/esaMI/Cassini-Huygens/index.html