charlie by xuyuzhu


									The Search for Life on Titan


     By: Charlie Congleton
          What do we need for LIFE?
• A fluid medium for transport of solutes

• A consistent energy source

• Environmental constituents and
  conditions compatible with polymeric
  chemistry on Titan’s surface
{Irwin and Shilze-Makuch, 2001}
                Titan Overview
•   Largest moon of Saturn
•   Surface temperature ~95 K
•   Atmospheric pressure ~1.5 bars
•   Nitrogen rich atmosphere (90% N,~5% CH4)
•   “Dirty” water-ice surface (NH4, C2H2, silicates)
•   Ammonia-water oceans at depth?
•   Hydrocarbon haze and transient clouds
•   CH4 precipitation and fluvial processes
•   Cryovolcanism
Shulze-Makuch and Grinspoon, 2005
             What do we need for LIFE?
• A fluid medium for transport of solutes
         – CH4, NH4 + H2O
• A consistent energy source
         – UV radiation, high energy molecules from
           photochemistry, endogenic geology, lightning
• Environmental constituents and conditions
  compatible with polymeric chemistry on Titan’s
         – Likely due to photolysis of CH4 and N into tholins in
{Irwin and Shilze-Makuch, 2001}
• Form from photolysis of N and
  CH4 in Titan’s upper atmosphere

• Could fall and make their way
  into NH4-H2O

• Breakdown into amino acids
  when they dissolve
• Cause reddish brown tint in
Cassini-Huygens Mission

                                    Carbon Cycling
   • How is the CH4 getting back into
     the atmosphere?
          – Methanogens
             • [C2H2 + 3H2 → 2CH4]
          – Methane clathrates
          – Cryvolcanism
   • Atmosphere is enriched with
     heavy nitrogen relative to heavy

     methane isotopes
          – Why? Biological? Geological?
Shulze-Makuch and Grinspoon, 2005
           Earth Analogue?
• Trainer et al., 2004 suggest that Titan’s
  haze may be similar to the one that may
  have covered prebiotic Earth
  – Greenhouse (CH4 and CO2 on Earth)
  – Formation of organic molecules
  – Methanogenic organisms
  – Food?

        What To Look For?
• Could be much larger than water-based
• Could metabolize slower
• Could use different biomolecules
• Might not use redox reactions
• Could be something weird we’ve never
  seen before
Atreya, S. K., E. Y. Adams, et al. (2006). "Titan's methane cycle." Planetary and Space Science 54(12): 1177-1187.

Collins, G. C. (2005). "Relative rates of fluvial bedrock incision on Titan and Earth." Geophys. Res. Lett. 32(L22202).

Fischer, G., T. Tokano, et al. (2004). "Energy dissipation of possible Titan lightning strokes." Planetary and Space Science 52(5-6): 447-458.

Hueso, R. and A. Sánchez-Lavega (2006). "Methane storms on Saturn's moon Titan." Nature 442(7101): 428-431.

Irwin, L. N. and D. Schulze-Makuch (2001). "Assessing the Plausibility of Life on Other Worlds." Astrobiology 1(2): 143-160.

Lunine, J. I., Y. L. Yung, et al. (1999). "On the volatile inventory of Titan from isotopic abundances in nitrogen and methane." Planetary and
     Space Science 47(10-11): 1291-1303.

Schulze-Makuch, D. and D. H. Grinspoon (2005). Biologically Enhanced Energy and Carbon Cycling on Titan? Astrobiology 5: 560-567.

Sotin, C., R. Jaumann, et al. (2005). "Release of volatiles from a possible cryovolcano from near-infrared imaging of Titan." Nature 435(7043):

Stofan, E. R., J. I. Lunine, et al. "Mapping of Titan: Results from the first Titan radar passes." Icarus In Press, Corrected Proof.

Tobie, G., J. I. Lunine, et al. (2006). "Episodic outgassing as the origin of atmospheric methane on Titan." Nature 440(7080): 61-64.

Tokano, T., C. P. McKay, et al. (2006). "Methane drizzle on Titan." Nature 442(7101): 432-435.

Tomasko, M. G., B. Archinal, et al. (2005). "Rain, winds and haze during the Huygens probe's descent to Titan's surface." Nature 438(7069):

Trainer, M. G., A. A. Pavlov, et al. (2004). Haze Aerosols in the Atmosphere of Early Earth: Manna from Heaven. Astrobiology 4: 409-419.

To top