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NASA Space Science

Tropical Lakes On Saturn Moon Could Expand Options For Life 84

Posted by samzenpus
from the going-for-a-dip dept.
ananyo writes "Nestling among the dunes in the dry equatorial region of Saturn's moon Titan is what appears to be a hydrocarbon lake. The observation, by NASA's Cassini spacecraft, suggests that oases of liquid methane — which might be a crucible for life — lie beneath the moon's surface. Besides Earth, Titan is the only object in the Solar System to circulate liquids in a cycle of rain and evaporation, although on Titan the process is driven by methane rather than water. This cycle is expected to form liquid bodies near the moon's poles, but not at its dune-covered equator. Now scientists think they have found a tropical lake — some 60 kilometers long and 40 kilometers wide, and at least 1 meter deep — in Cassini observations made between 2004 and 2008. Because tropical lakes on Titan should evaporate over a period of just a few thousand years, the researchers argue that these ponds and lakes are being replenished by subsurface oases of liquid methane. That would expand the number of places on the moon where life could potentially originate."
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Tropical Lakes On Saturn Moon Could Expand Options For Life

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  • by wisebabo (638845) on Thursday June 14, 2012 @03:46AM (#40319955) Journal

    Absolutely positively evidence that the universe was crawling with life!

    It would mean life is not only not based on DNA (and thus couldn't be a result of cross-contamination with earth as has been suggested might be the case for any Maryian life we might come across), but wouldn't even be based on WATER! It would mean that perhaps anywhere there was a liquid at perhaps almost any temperature we should be on the lookout for life! (Liquid helium on Pluto? Molton magma in the earth's mantle?)

    I read in the book "Life as we do not know it" that Titan could be the home to up to three(!) completely separate "Domains" (the authors term) of life. Water based (around some heated cryo-volcanoes perhaps), ammonia-water, and methane based.

    Someday we'll send a manned mission to orbit Titan. Then using remote balloons(!) and boats(!) they'll be able to really investigate these possibilities. Until then, the time lag will make things difficult (but not impossible I hope).

    • by Pfhorrest (545131) on Thursday June 14, 2012 @04:26AM (#40320099) Homepage Journal

      AFAIK there's nothing to say that methane-based life couldn't also use DNA. Methane is still carbon and hydrogen. All living organisms on Earth are composed primarily of carbon, hydrogen, oxygen, and nitrogen (CHON), and the general presumption looking for life elsewhere in the universe is that places with high concentrations of those elements is a good place to look, because we know life can be built out of them. Hydrogen and carbon dioxide are interconvertible with methane and water very much like carbohydrates (such as methane) and oxygen are interconvertible with carbon dioxide and water; all these processes involve the, C, H, and O of CHON equally, and the former was actually quite common early in the history of life on Earth. It wasn't until photosynthetic organisms started using light to convert CO2 and H20 into O2 and various CH's that the now-free O2 and CH4 reacted to become more of the H2O and CO2 that now cover our planet. (And then the O2 kept piling up and almost killed it all until some enterprising organisms started combusting it with those other CH's into more H20 and CO2).

      TL:DR; methane really isn't all that weird an environment to find life much like we know it. Molten silicon and iron, on the other hand, or liquid helium, that would require some as-yet-unknown chemistry).

      • by codewarren (927270) on Thursday June 14, 2012 @08:43AM (#40321315)

        Extreme cold, on the other hand, does reduce the odds of finding life. Not because things can't live in cold climate, but because evolution is ultimately a chemical process, and all chemical processes are retarded by cold. It took life on earth billions of years to evolve in a temperate climate. In a gigantic freezer, it could be expected to take much much longer.

      • by grep_rocks (1182831) on Thursday June 14, 2012 @10:02AM (#40322067)
        It takes more than just having the right elements to create life - water has some interesting chemical properties that methane lacks - such as it is one of the only chemicals which expands when it freezes, water is a polar molecule being slightly positive on one side and negative on the other, can form a large number of hydrogen bonds for its size, and especially relevant is that it is a fantastic solvent - all these properties are favorable for life, for example being a good solvent allows other molecules and ions to dissolve into water, allowing for lots of different types of chance chemical reactions to occur between different dissolved molecules - Methane is not as good a solvent as water, as it lacks polarity, however some people have proposed life working using poly-lipids as a substitute for proteins in non-polar liquids but because it is a poor solvent the chances of life working in a methane ocean seem less likely than water...
        • by myowntrueself (607117) on Thursday June 14, 2012 @11:15AM (#40322907)

          One of the things that contributes to 'life as we know it' is the lipid bi-layer which forms cell membranes.

          The lipid bi-layer is formed by molecules one end of which is hydrophobic and the other end of which is hydrophilic.

          One has to wonder if similar analogous molecules exist for methane instead of water? Ie methane-phobic on one end and methane-philic on the other.

           

          • Sure...the same lipids that are found in the phospholipid bilayer in our own cells. The hydrophilic end is methane-phobic, and the hydrophobic end is methane-philic. This would cause them to organize in the reverse direction so that the hydrocarbon tail is solvent-exposed. There seems to be some work on the subject, perhaps starting with Rand et al, Biochemistry, vol. 29, pp. 76--87 (1990), though it's really not my field so I'm not familiar with all the literature.

            • Sure...the same lipids that are found in the phospholipid bilayer in our own cells. The hydrophilic end is methane-phobic, and the hydrophobic end is methane-philic. This would cause them to organize in the reverse direction so that the hydrocarbon tail is solvent-exposed. There seems to be some work on the subject, perhaps starting with Rand et al, Biochemistry, vol. 29, pp. 76--87 (1990), though it's really not my field so I'm not familiar with all the literature.

              I wonder if they would function like this at the temperatures where methane is liquid?

              • My guess is yes. These effects are because of ordering in the system, which means the enthalpic gain is more than the entropic cost. The entropic cost is higher at higher temperatures. So if they display this behavior at room temperature, lowering the temperature to where methane is liquid (even at infinite pressure, the temperature has to be below about 180 K to get a liquid phase, if my memory of the coexistence curve is accurate) is going to reduce the entropic cost even further, which should make the

      • by Grishnakh (216268)

        Molten silicon and iron, on the other hand, ... that would require some as-yet-unknown chemistry).

        The Hortas would disagree with you.

      • by Anonymous Coward

        This may sound nit-picky to any non-chemist, but our terms are not up for discussion:

        carbohydrates (such as methane)

        Methane is not a carbohydrate. It's a hydrocarbon. Sugar is a carbohydrate. Carbohydrate: "carbon and water (water a. k. a. DHMO)"; hydrocarbon: "hydrogen and carbon".

        [...] photosynthetic organisms started using light to convert CO2 and H20 into O2 and various CH's

        No, they started using light to convert CO2 and H2O into O2 and carbohydrates, not hydrocarbons. Like:

        6 CO2 + 6 H2O -> C6H12O6 +

    • It was one of the last NASA / Esa proposals for an ambitious large mission, only, the thing was automated:
      http://en.wikipedia.org/wiki/Titan_Saturn_System_Mission [wikipedia.org] -nicknamed 'TSSM'

      In 2009 an easier-to-do competitor was chosen, to Jupiter (also because we already went to Titan with Cassini/Huygens, similarly a joint NASA/ESA mission), but TSSM does remains a convincing candidate for the next row of selection...

      Herve5, former tech. resp. of the Huygens probe to Titan ;-)

  • Rivers? (Score:4, Interesting)

    by MichaelSmith (789609) on Thursday June 14, 2012 @04:34AM (#40320131) Homepage Journal

    Maybe liquid methane flows from the poles to the equator and evaporates there. Then gaseous methane flows to the pole through the atmosphere and precipitates out.

  • There is no proof that there is any life at all. The paper(http://www.sciencedirect.com/science/article/pii/S0019103510001053- login needed) that interpreted the data from the Cassini mission has been questioned by Chris McKay (NASA http://www.spacedaily.com/reports/Have_We_Discovered_Evidence_For_Life_On_Titan_999.html [spacedaily.com]). The possibilities do NOT rule out life but comes out with other explanations that are more plausible.
    1. The determination that there is a strong flux of hydrogen into the surface is mist
  • by jbeaupre (752124) on Thursday June 14, 2012 @04:47AM (#40320177)

    Could it be a brew of organic compounds that would normally freeze, but with just enough methane to keep it liquid? The methane vapor pressure could be in equilibrium with the atmospheric methane. It'd also have to be some blend that doesn't want to slowly crystallize out the solute. So solubility would have to be high for the solutes.

    An Earth equivalent would be honey. Liquid, water based, stable, doesn't dry out.

    Chances are the authors have thought of this and rejected it. If someone could explain why, that'd be great.

  • Helium rain (Score:5, Informative)

    by arisvega (1414195) on Thursday June 14, 2012 @05:24AM (#40320281)

    Besides Earth, Titan is the only object in the Solar System to circulate liquids in a cycle of rain and evaporation

    No, [latimes.com] it is not [space.com].

    • by bytesex (112972)

      What about Venus ? I thought it rained on Venus, hot sulphuric acid, but still..

      • Re:Helium rain (Score:5, Informative)

        by arth1 (260657) on Thursday June 14, 2012 @08:01AM (#40321027) Homepage Journal

        What about Venus ? I thought it rained on Venus, hot sulphuric acid, but still..

        Yes and no. It rains sulphuric acid in the upper athmosphere (which is almost all carbon dioxide and so dense you can almost swim in it), but the rain never hits the ground.

        Still, Venus is - by far - the planet that resembles Earth the most. Much more so than Mars.
        Yes, it's more inhospitable too.

        • Re:Helium rain (Score:4, Interesting)

          by ShanghaiBill (739463) on Thursday June 14, 2012 @11:30AM (#40323095)

          Still, Venus is - by far - the planet that resembles Earth the most. Much more so than Mars.
          Yes, it's more inhospitable too.

          The surface of Venus is inhospitable. But people could live in the atmosphere. The atmosphere of Venus is so dense, that a floating city filled with an Earth-like atmosphere of oxygen+nitrogen would have enough buoyancy to float. The upper atmosphere is much cooler than the surface. Sunlight is more than twice as bright as on Earth, so there would be plenty of energy.

          • by Grishnakh (216268)

            One nice thing about Venus is its size and mass: it's nearly identical to Earth in both regards, and in gravity. Whereas tiny little Mars has only 1/3 of Earth's gravity.

            I wonder how hard it'd be to terraform Venus' atmosphere to be breathable, or at the least stop the runaway greenhouse effect and make it habitable to humans (wearing respirators outdoors). It seems like some clever, large-scale chemical reactions, probably with some kind of genetically engineered bacteria, would be a lot easier than tryi

    • No, helium rain does not operate in a cycle of rain and evaporation. The He takes a one way trip deeper into the planet depleting the outer atmosphere of He.

      • by arisvega (1414195)

        No, helium rain does not operate in a cycle of rain and evaporation. The He takes a one way trip deeper into the planet depleting the outer atmosphere of He.

        You could be right- but it depends on who you ask!

  • by Viol8 (599362) on Thursday June 14, 2012 @06:29AM (#40320599)

    We know on earth deserts can form in a few thousand years so why not on Titan? Perhaps that lake is the remenant of something much larger that formed when that part of the moon was far wetter a few thousand years ago?

  • by Lotana (842533)

    Guess we will call the lake "Clear Lake" [wikipedia.org].

  • Now scientists think they have found a tropical lake — some 60 kilometers long and 40 kilometers wide, and at least 1 meter deep ...

    What other bass fishermen out there read that of the summary and immediately thought, "Topwater!"

    (I'm going on a fishing vacation all next week. All I've been doing this week is planning rod setups, and posting to /. of course, to the detriment of my real work.)

  • below -160C, who in their right mind actually thinks that there will be life?

    • by Rogerborg (306625) on Thursday June 14, 2012 @09:41AM (#40321831) Homepage
      I'd love to think that right now on Titan some right-minded blob is telepathically ranting "But the melting point of dihydrogen monoxide is 273K! Nothing could live in such a hostile environment!"
      • by Nutria (679911)

        Sure, that would be great.

        But seriously, what chemical reactions actually happen in water ice?

        • by Patch86 (1465427)

          Water ice has nothing to do with hypothetical life on Titan. Liquid methane would replace water as the main solvent, so no water would be required. The freezing point of water therefore becomes irrelevant- it's the freezing point of methane that becomes a lower limit.

          • by idontgno (624372)

            Great. Let's rephrase GPP's rhetorical question to be precisely on-point to Titan.

            But seriously, what chemical reactions actually happen in liquid methane?

            Except I'm not being rhetorical. Can we even conceive of biochemistry at -161 C? Or do we have to speculate wildly?

            • by Patch86 (1465427)

              Again, temperature has nothing to do with it. The reason earthly life does poorly at sub-zero temperatures is because it is below the freezing point of our body's solvent (water). Different freezing points for different liquids mean different habitable temperatures for hypothetical life. Since Titan is the perfect temperature for liquid methane, a potential methane-based life form would also find that the moon's surface is the perfect temperature. Earthly temperatures would literally boil their blood.

              Obviou

  • by Papa Legba (192550) on Thursday June 14, 2012 @09:34AM (#40321735)

    Implications of the fact that step one in building a technology base/civilization is the discovery of fire, which for a methane based life source is not going to go over so well. I can only assume that development is going to be stunted in an enviroment where a strike anywhere match is the same equivilant as the deathstars laser.

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