5
$\begingroup$

I was making a planet for a game and I was wondering how the world would be affected if it never had salt water, but instead a huge fresh water supply. Then I thought about what it might do to the Earth.

Basically what would be the differences on Earth without salt water, or would it be relatively the same? How would the life on Earth be different? How would this affect the weather?

$\endgroup$
  • 2
    $\begingroup$ Posting as a comment because I don't have time to research atm, but basically a lack of salt water would imply a lack of sodium and/or chlorine on the planet. That would be bad for complex life as we know it because sodium and chloride are very import for biological mechanisms. $\endgroup$ – Jake Oct 6 '15 at 12:36
  • $\begingroup$ Perhaps chloride and sodium are only essential to life because life evolved in an environment in which they're plentiful. If they weren't present then life might have found other mechanisms using other elements. $\endgroup$ – Max Williams Oct 6 '15 at 13:06
  • 2
    $\begingroup$ Water is a "universal solvent." Salty water is water with things dissolved in it. It's awfully hard to have unsalty water if it's in contact with the ocean floor. $\endgroup$ – Serban Tanasa Oct 6 '15 at 13:10
  • $\begingroup$ @SerbanTanasa if your point is that the planet's crust would also need to be free of sodium and/or chlorine, then i think you're right. $\endgroup$ – Max Williams Oct 6 '15 at 13:11
  • 2
    $\begingroup$ @Jim2B It could be possible to have no salt water (or at least, no major bodies of salt water) on a planet without enough water to sustain oceans. Rivers would terminate in dry salt flats where the water would spread out and evaporate instead of in oceans. There'd be salt water near the ends of rivers where they entered the salt flats, but only in limited quantities. Cooler, higher altitude regions could still have liquid water, lakes, and rivers, though likely in substantially reduced quantity. $\endgroup$ – ckersch Nov 7 '17 at 16:24
4
$\begingroup$

Life on earth is based on a salt-water metabolism: we all carry around salt-water inside us to bathe our cells which evolved to expect that environment. So, with only fresh water, evolution would have had to happen in a completely different way: basically you're looking at rewinding the clock 4 billion years and seeing what happens without sodium and or chloride. My suspicion is that the various chemical processes which are running all the time in our cells could be done differently, with different elements, and you would get life which was broadly similar to the life we know, until you got down to the level of biochemistry. However, maybe the dependence on the alternative chemicals would push life in a completely different direction.

Basically you're looking at a total reboot of evolution, from the bottom up, and it's quite tricky to speculate what you're going to end up with after that.

EDIT - i forgot to think about weather and geology. I'm not particularly knowledgable about meteorology, geography and geology, but my guess would be thus:

The current state of the earth's physical geography is due to three main processes: rock formation, plate tectonics and weather. The rocks are formed, smashed together/pulled apart on the big scale by tectonics to make mountain ranges and valleys, and then weather erodes the rocks. In addition to this, tectonics and perhaps other geophysical processes move landmasses under and above sea level over huge time scales, so you have land that used to be on the sea bed now forming the earth's walkable surface, etc.

Since water evaporating from the sea doesn't take the salt with it anyway, the weather wouldn't be very different. In other words, i don't think that the oceans' salt content plays much part in the Earth's weather, because i don't think there's much salt in the atmosphere. I doubt that the salt content of the rocks plays much part in tectonics either. So, the only remaining aspect of the earth's surface which could be affected by the removal of sodium and/or chlorine would be the actual rock formation: perhaps we would have different kinds of rocks - in particular, we might have a smaller range of crystalline rocks in existence. But, i suspect we would still see the same broad processes, wherein tectonics and volcanoes make mountains, and the weather smoothes them out again, etc, and you have things like topsoil and silt and other "stuff" which change our planet's land surface from a bare rocky landscape into a softer "earthy" terrain which can support plants etc.

$\endgroup$
  • $\begingroup$ Ah I see. I wasn't sure how based life was on salt water. I guess it would be a throw in the air evolution wise. $\endgroup$ – Sunspear25 Oct 6 '15 at 13:17
  • 1
    $\begingroup$ No salt implies no iodide. Sea-life emits vast amounts of methyl iodide to the atmosphere. It oxidizes in the lower atmosphere, creating condensation nuclei, which probably have a major impact on meteorology. Also if life before oxygen also manufactured methyl iodide, it would accumulate in the methane atmosphere, and it's a very potent greenhouse gas. That might explain why the early earth wasn't a snowball. The sun was a lot cooler back then. $\endgroup$ – nigel222 Oct 6 '15 at 16:24
  • $\begingroup$ So the atmosphere itself would be different? Interesting. I didn't know the removal of salt would cause such a large effect. $\endgroup$ – Sunspear25 Oct 6 '15 at 18:14
  • 1
    $\begingroup$ Although a lack of salt in the oceans might not have a direct impact on weather, it might have an effect on ocean currents. Ocean currents are run by differences in salinity and temperature. Take away half of the equation and you could end up with vastly different current networks and thus different weather patterns. Scientists have long feared that melting glaciers in Greenland could chance the North Atlantic Current and freeze over the UK. We will have to wait and see if they are right. In short your ocean currents and weather patterns could be very different from what we know. $\endgroup$ – Josh Belmont Oct 11 '15 at 7:15
1
$\begingroup$

Actually, life evolved in (almost) fresh water. All the salt in today's oceans has weathered out of rock over the nearly four billion years since the steam clouds first condensed. On the other hand, at that time there was no oxygen atmosphere. If evolution had run much faster, your land-dwelling animals would have nearly freshwater blood, but they'd also have to breathe methane.

The salt levels in our blood that our metabolisms maintain almost certainly reflect the salt levels found in the oceans at the time some fishes evolved into air-breathing amphibians and left the oceans: rather less salty than today.

$\endgroup$
  • $\begingroup$ oh, that's very interesting, i didn't know that. Maybe evolution wouldn't have turned out so differently after all: we might have got to the same single-celled stage (which, in a way, is most of the battle won when it comes to life) and then diverged. $\endgroup$ – Max Williams Oct 7 '15 at 8:02
0
$\begingroup$

You probably will have to have some salinity in the larger water bodies because all vertebrate life forms (including fish and cetaceans) have a nervous system dependent on sodium/potassium channels. Not having any sodium at all in the waters would mean you cannot have fish there. Not having fish means you cannot kickstart vertebrate evolution there the way it happened on Earth.

All of which translates to say that no salinity in oceans or rivers (just a very minute level is required btw) means no backboned life on that planet.

$\endgroup$
  • 1
    $\begingroup$ You mean "Fish that are the same as the ones we know couldn't evolve". Just because the life that we know uses sodium & potassium, that doesn't mean that life could not evolve without those chemicals. Perhaps single-celled life would evolve using different mechanisms & elements, and in turn fish-like creatures would evolve, using those same mechanisms and elements. I don't think you can really say "Without sodium or chlorine it's impossible to have complex life". It's life, Jim, but not as we know it. $\endgroup$ – Max Williams Oct 6 '15 at 13:10
  • $\begingroup$ Actually, the multi-celled organisms which might evolve there will not be fishes as we know them. There might be complex life forms, but they will NOT be fishes. And as such, there will be no vertebrate group over there. Nobody said or implied that complex life couldn't evolve on that planet. What was said, was that vertebrate life forms cannot evolve there. Vertebrate is a strictly earthly term. $\endgroup$ – Youstay Igo Oct 6 '15 at 15:35
  • $\begingroup$ If by "fishes" you mean "fish-shaped organisms", I'd be very surprised if there won't be any. The fish shape is dictated by hydrodynamics. That's why whales and penguins and seals are basically the same shape, and why squid hold their tentacles so as to assume a similar shape when they want to move fast. $\endgroup$ – nigel222 Oct 6 '15 at 15:47
  • $\begingroup$ Organisms are more than a formation of skin only. Plus, I did mention cetaceans differently than fish. The context is clear. $\endgroup$ – Youstay Igo Oct 6 '15 at 16:30

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.