15
$\begingroup$

Apart from the obvious difference that liquid ammonia needs a much colder temperature than liquid water (but ammonia-based life forms wouldn't feel that as particularly cold), what would be the most obvious visible differences of an ammonia-based world compared to a water-based one, as seen by a life form on the ground?

For example, on a water-based world, common experiences, when living in the right place, would be ice on top of lakes. Since this is related to the water density anomaly, I guess this would not be the case for ammonia. But then, I couldn't find anything explicit about whether ammonia has such an anomaly, so maybe it would be a common experience on an ammonia-based world as well?

$\endgroup$
  • $\begingroup$ Your main problem is going to be the energy to maintain life. If it gets too cold on earth then life just stops running. Could an ammonia-based organism survive and metabolize in the ammonia temperatures? We just don't know... $\endgroup$ – Tim B Oct 24 '14 at 22:43
  • $\begingroup$ @TimB (and also OP) Are these supposed actual nitrogen based lifeforms, or just carbon backbone with nitrogen incorporated (which is what we have on Earth)? I think nitrogen based life is difficult because nitrogen can only make 3 bonds (vs. carbon and silicon making 4). I suppose you could have life just like on Earth, except adapted for cold and the very alkaline ammonia. $\endgroup$ – Superbest Oct 25 '14 at 6:37
  • 1
    $\begingroup$ @Superbest: I'd assume the life forms to be carbon based. Basically, nitrogen would replace oxygen, not carbon. $\endgroup$ – celtschk Oct 25 '14 at 12:20
  • 1
    $\begingroup$ @TimB: Of course water-based life has problems at temperatures much below freezing point, exactly because water freezes below freezing point (dissolved substances reduce the freezing point, but not arbitrarily much). I'd expect ammonia-based life to only have problems below ammonia freezing point. However, the lower temperatures might mean that all life processes are much slower. $\endgroup$ – celtschk Oct 25 '14 at 12:25
  • $\begingroup$ I dunno what it'd look like but it'd smell pretty bad! :-) (OK, not to anything that lived there, since they'd obviously not evolve to be able to smell ammonia, in the same way that we can't smell nitrogen or oxygen.) $\endgroup$ – David Richerby Oct 25 '14 at 15:39
13
$\begingroup$

Water has a few effects on Earth that come from it's properties.

  • Freezing and thawing of water comes at a very high cost of energy, and so does ammonia
  • Liquid water is most dense at 4 degrees, not freezing
  • Alkaline solubility of ammonia
  • Ammonia is combustible

One assumption - with the exception of Ammonia, the composition of the planet is mostly earth-like.

Standing on the planet, I imagine you will see very deep blue oceans. While Ammonia is colourless itself, trace amounts of alkaline metals present will give the Ammonia a deep blue appearance. 'Oceans' and other high ammonia to dissolved metals concentration would be very blue. Lakes and potentially rivers that have more metals dissolved will start to take on a metallic appearance and begin to conduct electricity very readily. Might make for some interesting arcing lightening storms on rivers and lakes.

'Ice' will be relegated to the depths of these lakes and oceans, not the surface.

Climate would be much simpler...currents and heat distribution systems on earth depend very much on the differing densities of water at different temperatures. In an ammonia world, the ice will be at the bottom with gradually warmer ammonia up to the surface. Your poles will be frozen with the 'tropics' being exceedingly humid (ammonia humid?). There's probably a narrow band between the two regions were it's hospitable to life...tropics and polar would only be available to them extremophiles.

Ammonia and water are on very similar levels as far as heats of entropy and fusion goes, so you would see a similar rate of daily warming and cooling. Ammonia actually changes it's specific heat capacity and takes more energy to warm as it gets warmer...so you may actually see less daily temperature changes due to heating.

No clue on feasibility, but Ammonia is quite flammable. If there is an oxygen component to your atmosphere, Ammonia will burn down to water and eventually NO2. Too be honest, I think a Ammonia world must lack oxygen by definition, if it did, it's probably turn into a nitrogen heavy atmosphere with water (earth much?)

Added:

Rivers might end up cutting far deeper in an ammonia world...water through calcium and alkaline metals does a little dissolving, but not much. On the other hand, Ammonia will be much more reactive and dig much further trenches. If This hypothetical planet and earth had a similar make-up, the rocky mountains would have huge trenches carved deep by flowing ammonia from the reactive with limestone.

$\endgroup$
  • 4
    $\begingroup$ Limestone would be unlikely to exist in an Ammonia based world. Limestone is formed from calcium in the shells of sea life - sea life in an Ammonia liquid would not use calcium for exactly this reason so would have to use something else or have no shells at all. $\endgroup$ – Tim B Oct 25 '14 at 6:30
  • $\begingroup$ Why do you think that rivers and lakes would have more dissolved materials than oceans? With water on earth, it's exactly the other way round: Oceans are salty because all the rivers put their minerals (salts) there, but evaporation doesn't remove them; rivers and lakes are generally less mineralized because the water in them is refreshed through (non-salty) rain, while the water flowing away takes the dissolved minerals with it. $\endgroup$ – celtschk Oct 25 '14 at 14:02
  • 1
    $\begingroup$ It seems to me that free oxygen in the atmosphere is quite unlikely on the ammonia world, it would quickly react with the ammonia. $\endgroup$ – Irigi Nov 18 '14 at 10:44
  • 1
    $\begingroup$ @irigi - exactly, it's what I meant by 'ammonia is combustible'. Free oxygen to any extent will react with ammonia and become water / NO2. There's a significant amount of hazardous material handling information around the combustibility of ammonia...apparently something thats only come up in more recent times too. $\endgroup$ – Twelfth Nov 18 '14 at 17:32
  • 1
    $\begingroup$ @Twelfth I only wanted to say that 'ammonia is combustible' doesn't only mean hazard of fires. It means that after few (thousands) of years, there either will be no free ammonia or there will be no free oxygen. But maybe you meant the same, I just wanted to point it out. $\endgroup$ – Irigi Nov 19 '14 at 8:58
5
$\begingroup$

As a solid, ammonia is considerably more dense than in its liquid form (see wikipedia). Thus, any ammonia that solidified would form at the bottom of lakes. This would be bad for any ammonia fishes around, as the ice that forms on the tops of water lakes prevents them from freezing further, thus preserving the fish. In an ammonia lake, it would not be inconcievable for the entire thing to freeze from the bottom up.

$\endgroup$
4
$\begingroup$

If it's raining ammonia it would look like Saturn:

Saturn’s upper atmosphere is mostly ammonia crystals while the lower one is either water or ammonium hydrosulfide. --Atmosphere of the Planets

@Tim B's comment about life:

One of the most resilient organisms known are tardigrades ("water bears"). Tardigrades can go into a hibernation mode — called the tun state — one that is more akin to "suspended animation" where­by it can survive temperatures from -253°C to 151°C, as well as exposure to x-rays, and vacuum conditions. --Life in Extreme Environments

If there were such a thing as "ammonia bears", they would find it quite lovely.

After reading the answers here, I would assume that any planet with a high enough concentration of ammonia would either have dissolved its own solid surface, broken down enough material so that it now includes water, or ultimately had no solid surface to stand on to begin with, like our gas giants.

JUPITER AND SATURN CLOUD LAYERS:

Ammonia clouds (150° K)
Ammonium Hydrosulfide clouds (200° K)
Water clouds (270° K)

enter image description here ~Cloudy, with a slight chance of death.

$\endgroup$
  • 1
    $\begingroup$ Water Bears are a good example, however I believe they are not active at the temperatures we are discussing. That's fine here as they can wait for a thaw. If the thaw never comes though it doesn't really help... $\endgroup$ – Tim B Oct 25 '14 at 6:33
4
$\begingroup$

More "cribbing:" I C-n-Ped this from a forgotten source. Although Haldane went at this in 1954, I believe the science is valid:

In 1954, J. B. S. Haldane, speaking at the Symposium on the Origin of Life, suggested that an alternative biochemistry could be conceived in which water was replaced as a solvent by liquid ammonia. Part of his reasoning was based on the observation that water has a number of ammonia analogues. For example, the ammonia analogue of methanol, CH3OH, is methylamine, CH3NH2. Haldane theorized that it might be possible to build up the ammonia-based counterparts of complex substances, such as proteins and nucleic acids, and then make use of the fact that an entire class of organic compounds, the peptides, could exist without change in the ammonia system. The amide molecules, which substitute for the normal amino acids, could then undergo condensation to form polypeptides which would be almost identical in form to those found in terrestrial life-forms. This hypothesis, which was developed further by the British astronomer V. Axel Firsoff, is of particular interest when considering the possibility of biological evolution on ammonia-rich worlds such as gas giants and their moons (see Jupiter, life on).

On the plus side, liquid ammonia does have some striking chemical similarities with water. There is a whole system of organic and inorganic chemistry that takes place in ammono, instead of aqueous, solution.4, 5 Ammonia has the further advantage of dissolving most organics as well as or better than water,6 and it has the unprecedented ability to dissolve many elemental metals, including sodium, magnesium, and aluminum, directly into solution; moreover, several other elements, such as iodine, sulfur, selenium, and phosphorus are also somewhat soluble in ammonia with minimal reaction. Each of these elements is important to life chemistry and the pathways of prebiotic synthesis. The objection is often raised that the liquidity range of liquid ammonia – 44°C at 1 atm pressure – is rather low for biology. But, as with water, raising the planetary surface pressure broadens the liquidity range. At 60 atm, for example, which is below the pressures available on Jupiter or Venus, ammonia boils at 98°C instead of -33°C, giving a liquidity range of 175°C. Ammonia-based life need not necessarily be low-temperature life!

Ammonia has a dielectric constant about ¼ that of water, making it a much poorer insulator. On the other hand, ammonia's heat of fusion is higher, so it is relatively harder to freeze at the melting point. The specific heat of ammonia is slightly greater than that of water, and it is far less viscous (it is freer-flowing). The acid-base chemistry of liquid ammonia has been studied extensively, and it has proven to be almost as rich in detail as that of the water system. In many ways, as a solvent for life, ammonia is hardly inferior to water. Compelling analogues to the macromolecules of Earthly life may be designed in the ammonia system. However, an ammonia-based biochemistry might well develop along wholly different lines. There are probably as many different possibilities in carbon-ammonia as in carbon-water systems. The vital solvent of a living organism should be capable of dissociating into anions (negative ions) and cations (positive ions), which permits acid-base reactions to occur. In the ammonia solvent system, acids and bases are different than in the water system (acidity and basicity are defined relative to the medium in which they are dissolved). In the ammonia system, water, which reacts with liquid ammonia to yield the NH+ ion, would appear to be a strong acid – quite hostile to life. Ammono-life astronomers, eyeing our planet, would doubtless view Earth's oceans as little more than vats of hot acid. Water and ammonia are not chemically identical: they are simply analogous. There will necessarily be many differences in the biochemical particulars. Molton suggested, for example, that ammonia-based life forms may use cesium and rubidium chlorides to regulate the electrical potential of cell membranes. These salts are more soluble in liquid ammonia than the potassium or sodium salts used by terrestrial life.

On the down side, there are problems with the notion of ammonia as a basis for life. These center principally upon the fact that the heat of vaporization of ammonia is only half that of water and its surface tension only one third as much. Consequently, the hydrogen bonds that exist between ammonia molecule are much weaker than those in water so that ammonia would be less able to concentrate non-polar molecules through a hydrophobic effect. Lacking this ability, questions hang over how well ammonia could hold prebiotic molecules together sufficiently well to allow the formation of a self-reproducing system.

$\endgroup$
  • 1
    $\begingroup$ This is from daviddarling.info/encyclopedia/A/ammonialife.html, which itself modified it lightly (with attribution) from 'Xenology: An Introduction to the Scientific Study of Extraterrestrial Life, Intelligence, and Civilization by Robert A. Freitas, Jr.' xenology.info/Xeno/8.2.2.htm $\endgroup$ – Tharaib Feb 10 '17 at 7:56
  • 1
    $\begingroup$ Welcome to WorldBuilding.SE! Interesting start, very detailed answer. $\endgroup$ – Secespitus Feb 10 '17 at 18:18
3
$\begingroup$

I am not sure about ammonia, but for example on the moon Titan, there are lakes of liquid methane, theoretically there is nothing in chemistry that prevents life from forming based on liquid methane as a medium instead of water, but we still don't understand what is life anyway to have a definitive answer about that. Scientists found from the Cassini–Huygens mission that hydrogen levels near the surface of Titan are lower than it should be and its much higher on the upper atmosphere, which is consisting with a previous prediction made by Chris McKay and Heather Smith that if there is methane based life on Titan they would breath hydrogen and infuse it with acetylene to produce energy. There is a consisting flow of hydrogen from the upper atmosphere to the surface of Titan but it just disappears. one interesting prediction for such a life form is that it will have really slow metabolism, way slower than plants.

$\endgroup$
2
$\begingroup$

The problem with swapping ammonia for water is that unlike water, ammonia ice is denser than liquid ammonia and therefore sinks instead of floating as ice does in water.

The layer of ice that forms on water isolates the body of water underneath preventing it from freezing further but with ammonia, the top freezes, sinks, exposes the next layer which freezes sinks and so on until the the entire body of ammonia is frozen solid. In principle, if you had ammonia sea in temperature ranges analogous to water on the earth, the entire ocean would likely eventually freeze solid and with it the planet.

So, to start, if you want oceans on your ammonia world, would have to be relatively warm and uniformly so as ice formation would be very dangerous to the entire ecosystem. A possible way around this problem would be to postulate that the planet has very hot core like Europa and therefore ammonia ice that sinks, melts as it descends. That would also provide a lot of energy to the ecosystem even if the planet is far from the sun.

As noted by twelth, Ammonia forms a lot of stable complexes with many metals so likely any ammonia oceans would very complex mixtures or pure ammonia and various ammonia compounds. More interesting, some of these compounds are immersible to each other i.e. they don't mix and instead form layers when tossed together so an Ammonia ocean might have various layers, bubble or pockets of vastly different properties.

Now just snowballing but highly electrically conductive water masses could provide the basis for life forms that move electrons directly, as current instead of using long chains of chemical reactions hand offs e.g. the Krebs cycle.

Thermal plumes in the deep ocean could drive separation of charges by moving vast masses of conductive ammonia metallic compounds which could create the electricity to that form the basis of the ecosystem much like sunlight does on earth. Also, energy imparted to compounds that the heat breaks apart and reforms would also eventually be released electrically.

An organsim that moved electrons directly could could absorb and expend a lot of energy even at cryogenic temperatures. Instead of something sluggish as a glacier which you would get with cryogenic chemical energy transfer, you'd get something cold but fast, likely something working like a superconductor which gets more efficient and faster and deadly as it as it gets colder.

Whole different class of critter from your standard bags of carbon filled with water which move at, least face it, the speed of diffusion

Such organism would likely have fewer cells or compartments as they would not need as many chemical isolations pockets. They might be collections of giant i.e. nearly visible cells. Since moving electrons is the their primary form of mode, likely all the cells are long and fiberous. The creatures might appear to be made of woven strands of neurons with ammonia-metalic polymer membranes. Physically appearing relatively simple, they might give the vive of simplistic rag-dolls compared to complex earth life, their complexity would lay in their invisible electrical fields and circuits formed on, between and and inside their giant cell membranes.

If all the water masses are conductive possible with various immersible channels routing currents, then likely the land biosphere might evolve as electrically connected as well. On earth, its been argued that life on land more or less dragged the sea along inside it. The same basic phenomena would wire up the land biosphere into the planetary circuit as well.

The entire biosphere might resemble something more like a planet of self-reproducing robots always on the lookout for current to tap and steal. Instead of eating prey for the energy in the chemical bonds of the preys flesh, they would just short the prey organism and drain its charge taking little or no matter from the kill. But shorting the membranes might cause the giant cells or tissues to just fall apart leaving a dust of raw materials.

Good story potential. Usually the idea of organic life forms posing any serious threat to a high tech space ship and crew landing on a planet is silly. We snuffed the earth's megafunga with pointed stick and the most bad ass predator that every walked the earth wouldn't last 60 seconds against your typical Marine and couldn't get past the least metal barrier.

But a critter in an electro-ammonia based world all in spooky perpetual twillite far from any sun.

  1. A ultra cold environment that makes metals and plastics brittle,

  2. Organisms that have no circulation, and possibly no real critical vital areas that sharp sticks or bullets can poke holes in.

  3. That moves at electrical and not biological speeds,

  4. that has possibly actually armored metallic flesh

  5. Whose strength is determined by voltage and amperage instead of muscle so the more juice it gets, the stronger it gets.

  6. Which can both absorb and project electricity

  7. which will likely have have radio or magnetic based senses senses

  8. That might be adapted to short out electronics and jam radar and radios.

  9. That sees a human in a space suit as a walking battery for lunch

  10. and sees the spaceship as an all you can eat buffet.

Well, now that that would make that all acid-for-blood critter Ellen Ripley had such a tussle with look like bit of a pansy wouldn't it? That little fluff ball just chased humans around the ship, it didn't try to wreak the ships systems, drain its power and maybe absorb its hull destroying all hope for survival.

The electro life form would likely completely ignore the humans but would head straight for the technology that makes us humans badasses instead of frozen meat-bags on a cryogenic world. Metal, electricity, plasma weapons (Plasma though hot conducts electricity) etc wouldn't be impediments to the creature but food. The more high tech you brought to the planet and whipped out for the defense, the stronger and more attracted the monsters would get.

They might not even notice the humans but if they humans couldn't stop the creatures from ripping apart their space suits, draining the ships power or tearing it apart for pure metals, the crew would die just as horribly as if the things actually tried to eat them.

$\endgroup$
0
$\begingroup$

I'd like to point out one of my favorite authors, Robert L. Forward, described such a world in Flight of the Dragonfly (later Rocheworld). The downed exploration plane, floundering in the ammonia sea, had the cleanest windows in ten lightyears.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.