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Does Water Really Have To Mean Life? 23

Posted by Cliff from the questioning-popular-myths dept.
bigweenie asks: "With the frozen mud on the Moon's pole and the springlike seepage of water out of the lowest valley walls of Valles Marinaris, everyone seems to have a heightened urgency and hope to find life on the Red Planet (past or current). My question is, what is the link between water and life? What exactly is the biochemical, environmental, evolutionary, physiological and, God forbid, logical evidence that water is suggestive of life? All the Mars 'search for life' experts have spent the last 20 years proving life can exist anywhere under almost any conditions; no oxygen, no H2O, etc. I wish to know the real hard data and analyses that defines the relationship between water and life, and how optimistic should we be about life on Mars just because it is there in abundance." Assuming that other life exists, it is possibility of extra-terrestrial life similar to earth-life that provide a good deal of momentum to our collective interest. Since water is an absolute necessity for Earth based life, it is assumed that the presence of it elsewhere may mean the presence of lifeforms closer to what we know and understand.
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Does Water Really Have to Mean Life? More

Does Water Really Have to Mean Life?

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  • The search for water on the moon wasn't for life, rather, it was for a place to build a moon base. Reason? All multicellular earth life needs water to survive (inlcuding us). So, if we're looking for multicellular life outside of earth, we will start by looking for water. There are other issues that affect this - life needs some liquid, and of the choices (which boil down to Ammonia, Methane, and Water) water usually is the best option, from what I remember. This means that best place to look for non-earth life is where there is water.

    First post?

  • Also, most people don't even know that they really did find life on mars. In one of the first experiments that sent a robot to mars, it mixed some of the soil with a liquid (oxygen or water or something) which released a chemical that signified life. The experiment was dismissed because they didn't think enough of the gas was released to prove life. We we say life on mars, we mean microbes and littlie microscopic critter thingies. Also, the pervious post about life existing without water is right on. NASA and the US govenrment are just trying to create a lot of PR, trying to show that they're actually doing something
  • Water is not necessary for all life but most life we know needs it or lives in it. It helps do many things that is important for most life on every planet pass earth. Water needs huge amounts of BTU's to go from ice to water from water to steam and back. The Latent heat of water helps regulate the heat of a planet as it spins in space. This helps keep earth warm at night and this helps with life here. It also helps tell how old a planet is for water will evaporate or sublime off most smaller planets (not enough gravity to hold it down) in to space, a reason believed that mars has signs of being very wet in the pass but seems very dry now. The discovery of Ice on the moon puts its age in to question. Why is the ice still there after all of this time. Some are thinking A. the moon is newer than the earth or mars or B. ice keeps falling on it via meteors. Water is a very important thing to know about on other planets not to mention it helps us not to have to carry as much water with us if we come over to visit.

  • Think different (Score:3)

    by Kondoor ( 135852 ) on Thursday July 13, 2000 @09:15AM (#936559)
    people keep thinking of carbon based life forms when they think of life, and water goes right along with it. Who is to say that there can't be life based on pure enery, or a crystal of some type that has no carbon or is based of any elements we even know of. Think different, just because we don't know about it yet doesnt mean it doesnt exist.
  • Water is certainly what WE need for life. So when you're talkin' about a place like Mars, the existance of water fills two needs. First of all, there's a real desire in some circles to change the role of astronaut back from "glorified truck driver" to "explorer". The only way to be an explorer is to go somewhere new. The only way to get any major government or world consortium to pay for it is to prove it has some specific validity, scientifically and probably economically.

    So the chance of life, as we know it, goes hand in hand with the discovery of water on a planet. But more to the point, if there's water there, reasonably accessable, we can stay there indefinitely. If not, we'll have no permanent presence with our level of technology.

  • Fer instance, unlike most every other substance we know of, water gets less dense in it's solid phase. This means that ice floats.

    Think of a world where ice was denser than water. When the temperature was below 0 C, the ice would form, and sink. More ice would form, and sink. Eventually, your world would be solid ice.

    Since ice is less dense than water, ice forms on top of the water, and the water below is someone insulated, making a sort of haven for life to exist.

    Also, since water is a liquid, it makes a nice media for the transport of useful chemicals, and the removal of dangerous chemicals. An organism that is not suspended in water needs some sort of motivational method (legs, wings, rippling snail muscles) to get to food,and to mate. A waterborn critter can just float and hope for the best.

    Someone else mentioned water being a solvent, which helps for little critters getting foodies and stuff.

    George
  • which boil down to Ammonia, Methane, and Water

    What a confusing way to talk about liquids!
  • it's more of along the lines is that we're carbon based and need water, so a reasonable place to start looking for life would be to search for carbon based life that needs water. You've got to start somewhere, and it seems as logical as any other place. Silcon is also popular for life based, because it shares a lot of properties with carbon.
  • Actually, this is a two-way street. Water can lead to life via it's peculiar properties (solid less dense than liquid, etc).

    But also note that life can lead to water. What do you need to make water? Free oxygen. And what's the best place to get free oxygen? Photosynthesis.

    Clearly neither of this is set in stone. But Earth's two most obvious features are: 1) Life and 2) Water. That's probably not totally accidental.
    --
  • Who is to say that there can't be life based on pure enery, or a crystal of some type that has no carbon or is based of any elements we even know of.

    There might very well be.

    But the conditions on the moon, Mars et al are not completely different from Earth. Most if not all objects within our solar system were formed from the same glue. Therefore it is very logical to look for carbon based life forms that require water and thus to look for water.

    Looking for water on the moon and Mars makes even more sense, because we are not just looking for Et but also for a possible habitat for ourselves.

    Of course there migh be crystal based lifeform. But since we haven't encountered anything like it right here on Earth we wouldn't even know what to look for out there, would we?

  • If you've been watching Survivor you know that water does not represent life.

    Fire represents life. That's why they snuff out the torches at the end of every episode when someone is booted from the island.

    C'mon... we need to be watching more TV!!
  • The interesting thing about all this is that all these options are 'not quite as good' as the carbon/oxygen/water approach.

    Hence natural selection suggests we won't find any :-)

    You would need to construct an environment with an adundance of (one of) the 'exotic' alternatives and a scarcity of the common one before you would expect to see life.

  • Water for Life (Score:4)

    by fremen ( 33537 ) on Thursday July 13, 2000 @10:35AM (#936568)
    Water has quite a few properties that make it REALLY useful for life.

    The thing about water is that it has a tremendous polarity associated with it. The oxygen atom tends to be electronegative, pulling the electrons away from the hydrogen atoms. Why is this important? The polarity of the molecule makes water an EXCELLENT solvent, meaning that things dissolve in it easily. This means that water can transport atoms between cells more efficiently.

    Perhaps the most important effect of this polarity is the hydrophobic aspect of water. The polarity of the water molecules make it adhere to other water molecules when in the presence of non-polar molecules, such as organic chemicles (which is why oil and water do not mix). This is CRITICAL for the formation of cell membranes. Cell's have a layer of lipids on the outside that are held together by the hydrophobic pressure of water molecules.

    Another benefit of water's polarity is that it floats when frozen. This keeps it from accumulating on an ocean floor where it can never melt, taking valuable things that are dissolved within the molecules with it. Since ice floats, it can theoretically melt and refreeze in a fairly constant pattern, assuming the planet is warm enough. If water didn't float, we would have never left the first ice age!

    I would think that any highly polar molecule would work similarly to water, but very few exist. The biggest problem is that most of them are normally either gasseous or solid. Some are too complex to expect them to normally form in large enough quantities to support life. I'll grant that there is no way we could know everything about life and the universe, but it's a safe bet to guess that life will be involved with water.

    For more information, go to Google and search for 'water biochemistry'. Enjoy.
  • I haven't heard of Sagan's Lifeform, but in Clarke's Odyssey trilogy (was it _2010_ ?), Dave Bowman travels through the clouds of Jupiter and witnesses living clouds, with predators, social interaction, and the like. It's a really neat idea, and Clarke even explains that these lifeforms could NEVER develop real intelligence, because they evolved more like amoebae than proper animals. He takes great care to describe Jupiter's (theorized)diamond core, too.
  • Well, yeah. :-) Earth kind of has the correct conditions for H20/02/Carbon based life to work best. things might be different elsewhere :-)

    A wealthy eccentric who marches to the beat of a different drum. But you may call me "Noodle Noggin."
  • carbon based life forms are all we think about because too many people's heads would explode if they met a "superintelligent shade of the color blue."
  • according to the classic definitions of life, water is neccisary for life, and the current projects looking for water on other planets are really searching for the potential for life. a more radical question would be, does life really have to mean water?

    the scifi fans out there i'm sure have heard of silicon based life. by that i mean organisims that are based on silicon rather than carbon. the chemical reactions that would keep such an organisim going might not need water in the way that caronic organisims do. there may be other elements that may be just as versital as silicon and carbon.

    now, the meat: are we as a culture (and as a scintific community) ready to accept non-orgainic "life" as life? i'll leave the obvious AI questions to other posters.
  • I'm not too familiar with the details of that experiment, but I believe that the soil's reaction was later demonstrated to be better explained by non-living chemical reactions. Martian soil is full of reactive substances like peroxides and superoxides that can do interesting things.
  • Other things like like hydrochloric acid might work, but it is a bit strong of a solvent But to have Hydrchloric Acid, you have to have water. :) HCl can exist as a gas, or dissolved in water. I am not aware of it existing as a anhydrous liquid, but maybe under the right conditions, great pressure or low temperature, it could... I am too lazy to look it up right now.
    -----------------------------

  • Alternative Forms of life (Score:4)

    by The Iconoclast ( 24795 ) on Thursday July 13, 2000 @12:08PM (#936575)
    Ok, now for some alternative Biochemistries!!

    -Silicon Based Life: This would be based upon silicon instead of carbon. We (and evrything else living on earth) are based on Carbon. Why? Because carbon just so happens to have a valence shell of 4 electrons meaning that it can accept 4 more electrons or donate 4 more electrons. This leads carbon being able to form all sorts of nifty compounds such as rings (benzene, sugars) and chains (hydrocarbons, starches, proteins). Silicon also has 4 valence electrons, so theoretically, it could form all sorts of nifty compounds, too. However, because of some quantum chemistry issues, silicon does not perform quite as well as carbon in forming chains and rings. Silicon is much better for forming nifty crystals as we all know :-).

    -Sulfur breating life: We breathe oxygen. Why? Because in order to release the energy stored in fats, sugars, and protiens, they must be oxidized (burned) and we use oxygen to do that. Even plants use oxygen (in small amounts) to metabolize the sugars they produce from photosynthesis. There are forms of life on Earth that do not use oxygen at all, these are chemotrophs (chemical eaters) who live in volcanic vents on the ocean floor and such. They tend to combine and split different chemicals to release the requisite energy for life. Some of them use Sulfur as an oxidizer instead of oxygen. Theoretically Carbon Monoxide, ozone, or even a halide (Chlorine, florine, bromine) could be used.

    -Ammonia bathed life: Water is incredibly important for us, because as mentioned earlier, it is an excellent solvent for all the chemical reactions that make up life to occur. Also as mentioned earlier, there are not too many simple molecules that are liquid and polarized at decent temperatures. Water is one of them. Ammonia (NH3) is another. However, ammonia is slightly less polarized than H20 and therefore it doen't quite work as well as water. Other things like like hydrochloric acid might work, but it is a bit strong of a solvent :-) Things like benzene and hydrocarbons and liquid chlorine are not polarized so they really wouldn't work.

    As for other things (energy-based life, etc.), although we cerainly do not know enough to completely rule out this type of life, chances are that any based on vastly different chemistry from our own (or NOT chemistry) would find it difficult to communicate with us.

    By the way, I am a physics student, so this is a small step down for me (just kidding :-). I did watch lots of Nova and stuff when I was younger.

    A wealthy eccentric who marches to the beat of a different drum. But you may call me "Noodle Noggin."
  • People continue to think of life as carbon based because it is possible to imagine carbon based life forms. After all, all life I have ever seen is carbon based. I think your statement that there could be life out there totaly diffrent than anything we know is valid, but we cannot take the idea farther that that without coming across it. You can think up anything you want but it is almost definatly not accurate. So we look for what we know. Then at least we know what we're looking for.
  • Until someone invents "Mr Spock's Tricorder", boffins will continue to have a hard time scanning for "life signs" that are outside of humanity's current field of experience.

    Until such time as mankind actually makes contact with a form of life that functions along different principles to our own Earthling bodies, what do you look for?
  • Hm, you mentioned that most of these polar molecules are either gaseous, or solid. On Earth maybe. What if you raise or lower the temperature or atmospheric pressure.

    I mean, on Star Trek all they ever do is land on Class M planets that are perfect for human, and other, life. What about planets where the atmospheric pressure, or temperature, is high or low enough to maintain these other possible molecules in an ideal life-giving state?

    It wouldn't be much fun trying to colonise one of these places though ;-)

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