1 / 32

Enceladus and Titan: Prime targets in the search for life

Enceladus and Titan: Prime targets in the search for life. Enceladus. Enceladus is a moon of Saturn, 1000 times smalller than Europa , with jets emanating from hot crevasses. The jets are icy particles frozen from salty water. Titan 2nd largest moon in the sol sys

yan
Download Presentation

Enceladus and Titan: Prime targets in the search for life

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Enceladus and Titan: Prime targets in the search for life

  2. Enceladus

  3. Enceladus is a moon of Saturn, 1000 times smalller than Europa, with jets emanating from hot crevasses. The jets are icy particles frozen from salty water.

  4. Titan 2nd largest moon in the sol sys Density 1.88 g/cm3 -->rock+ice Dense N2-CH4 atmosphere. Surface 89-94 K; pressure 1.5 atm.

  5. Titan’s atmosphere NB – 1D radiative transfer codes are able to produce matching temperature profiles by including what we know about Titan’s composition

  6. Cassini-Huygens

  7. Cassini-Huygens INMS shows complex chemistry in the region above 900 km (probably below, too).

  8. Surface mass spectrum from Huygens

  9. Photochemistry at the heart of Titan’s surface-atmosphere evolution ethane λ < 1450 Å λ ≈ 2000 Å methane acetylene HCN nitrogen

  10. Quantification of the methane consumption (simplified) Net photochemical destruction rate of CH4 (Lavvas, et al. 2008) p-l= -3.5 x 10-13 g cm-2s-1 referred to the surface Mass per area of methane in atmosphere ~ P/g = 370 g cm-2 Lifetime of atmospheric methane: -P/g(p-l) = 35 million years Amount of methane that must be supplied to the surface over time Need 4.5 x 109 years /3.5 x 107 years ~ 100 x present atmospheric methane over the age of the solar system. or 100P/g = 3.7 x 104g cm-2 / (0.7, 0.4 g cm-3) = (0.5, 0.9) km thick layer of (C2H6, CH4) over the age of the solar system Methane must be resupplied through time by outgassing from the interior.

  11. Ligeia Mare: One of Titan’s great seas 100 km

  12. 2009 2005 Ontario Lacus

  13. Hayes et al, 2009 Loss of liquid of ~ 86 km3 , av. depth 5 meters  5 m layer lost over 5 years

  14. Moriconi et al 2010. Cassini VIMS data.

  15. Titan’s Milankovitch cycles: precession of Saturn’s eccentric orbit

  16. Cycling of lakes/seas on Titan Seasonal Croll-Milankovitch Ethane/propane-rich Methane-rich Lower viscosity waves Croll-Milankovitch 50,000 years “Hydration/dehydration” cycling Seasonal 30 years Higher viscosity smooth Precipitates (C2H2, HCN…) Ethane/propane-rich No analog exists in Earth’s hydrologic cycle for this kind of complexity

  17. Cassini surface mysteries • There is a sink of hydrogen at the surface • Acetylene is underabundant in surface deposits • Benzene is present in surface deposits • Ethane is 100-1,000 times less abundant than expected on the surface.

  18. Titan surface reactions? Methanogenic C2H2+3H22CH4 + 334 kJoules/mole (McKay and Smith, 2005) Chemistry 3C2H2C6H6

  19. Could this Titan host life on its surface? At -180 C liquid water is not stable at the surface. However, should one rule out a priori a form of life that exists in ethane and methane….?

  20. What’s right with water as the host liquid for biochemistry • Excellent solvent for salts • Polar • Provides an “inside” and “outside” for biopolymers

  21. Could methane and ethane act as a liquid medium for life? • Allows organic molecules to hydrogen-bond • Polar hydrocarbons associated with the liquid might create “insides” and “outsides” in liquid ethane/methane • “Biological” molecules would be dominated by C-N bonds rather than C-O as on Earth. • Some C-O compounds resulting from interaction with water-ice bottom. Steve Benner and colleagues

  22. Titan has a big advantage over other astrobiological targets Life in ethane-methane seas on Titan is a far more stringent test of a separate second origin than life found on Mars, Europa, or Enceladus. Impact exchange of material between bodies in our solar system implies a fundamental difficulty in proving that life “like us” had a separate origin. Life in a hydrocarbon sea is so fundamentally different-- at the molecular level—that it immediately would imply a second, separate origin of life. ? Titan No planetary protection issues: landing in the hydrocarbon lakes sterilizes the probe. Easy access to the lakes: no radiation, no drilling, just repeat Huygens mission....

  23. “ If life is an intrinsic property of chemical reactivity, life should exist on Titan. “Indeed, for life not to exist on Titan, we would have to argue that life is not an intrinsic property of the reactivity of carbon-containing molecules under conditions where they are stable.” Limits of Organic Life, National Research Council 2007 LPL/JPL/NASA/USGS

  24. TiME: The Titan Mare Explorer A Discovery Mission to an Extraterrestrial Sea

  25. We must go back to the Saturn system...if we want to test whether the origin of life is a common cosmic phenomenon

More Related