<p>The article <a href="https://www.science.org/doi/abs/10.1126/science.1155432" rel="nofollow noreferrer">&quot;Water Activity and the Challenge for Life on Early Mars&quot;</a> finds that the early Martian ocean would have been acidic and almost as salty as the dead sea.</p>
<p>The estimates for salinity of the Europan ocean vary widely, but most place the salinity <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103507000656" rel="nofollow noreferrer">above 50 g/kg</a>, more than that of sea water (about 45 g/kg).</p>
<p>You couldn't drink it, but there are plenty of life forms that are adapted to this level of salt.</p>

CC BY-SA 4.0
2022-03-14T00:01:24.947Z
`+1` but it's important to note that this is "educated speculation" rather than scientific fact or a widely held certainty. That there once was surface water now beyond reproach, but guesses about what the water was like exactly may evolve as more information becomes available. And as on Earth, since there was likely to have been rainfall and potentially less tidal mixing (no giant moon, further from the Sun), there could certainly have been a variety of different salinities rather than just one.
uhoh
CC BY-SA 4.0
2022-03-14T00:27:37.370Z
To that end I've just asked in Earthscience SE [How large were Mars' ocean tides and to what extent did they would keep the oceans mixing and tend to keep salinity uniform? Has this been modeled?](https://earthscience.stackexchange.com/q/23612/6031)
uhoh
CC BY-SA 4.0
2022-03-14T16:54:30.383Z
That said, you could purify the salty water to make it potable - something worth considering since it'd be easier to send desalination equipment than to send a large quantity of fresh water if there's enough usable water already there.
Darrel Hoffman
CC BY-SA 4.0
2022-03-14T17:54:17.603Z
It's a little better than "speculation".  It is a peer-reviewed article published in *Science*, one of the world's top academic journals.
James K
CC BY-SA 4.0
2022-03-15T02:09:56.923Z
“Best-effort” scientific speculation or extrapolation from limited data can always be published in reputable journals as long as it’s presented as such, it gets the conversation started and provides methods and frameworks for further analysis. It also sends your citation count skyrocketing when it’s the first in a long series of papers that unfold when more data is available that might in fact support the opposite conclusion. I’ll take a look at the paper and see what’s there, but absolutely nothing wrong with deductive speculation.
uhoh
CC BY-SA 4.0
2022-03-15T02:13:13.073Z
My point is only that it’s *quite possible* this is wrong. I’m sure looking back through *Science* for articles about Earth’s surface 3.5 billion years ago we can also find plenty of wrong conclusions. Scientific research is always “best-effort” whether we say it like that or not.
uhoh
CC BY-SA 4.0
2022-03-15T02:42:39.840Z
and by coincidence to illustrate that point, this just showed up in google news feed: [Scientists propose a new mechanism by which oxygen may have first built up in the atmosphere](https://phys.org/news/2022-03-scientists-mechanism-oxygen-built-atmosphere.html) links to the *Nature Communications* paper [Oxidative metabolisms catalyzed Earth’s oxygenation](https://www.nature.com/articles/s41467-022-28996-0) Anyway still `+1` for the answer!
uhoh
CC BY-SA 4.0
2022-03-15T04:57:37.040Z
Yeah there does exist a spectrum for which something is "science" but still speculation. A lot of paleontology lives in this zone. We know what the bones look like, but we are taking the most educated guess we can as to what these extinct creatures looked like, and the science is in refining those guesses hoping some evidence shows up eventually that can settle the matter.
Shayne
CC BY-SA 4.0
2022-03-13T21:10:31.360Z
2022-03-14T20:25:48.097Z
2022-03-14T20:25:48.097Z
James K
<p>Was Mars' ocean 3.5 billion years ago salt water or fresh water?</p>
<p>On a related note: would we be able to drink the water that is on Europa?</p>

CC BY-SA 4.0
2022-03-14T04:22:44.683Z
Europa: https://astronomy.stackexchange.com/questions/40239/is-the-water-underneath-europas-ice-cap-potable
Nilay Ghosh
<mars><water>
Salinity of Martian water 3.5 Billion years ago
Peter U
# Salinity of Martian water 3.5 Billion years ago

(Asked by: username_0 on 2022-03-13)

Was Mars' ocean 3.5 billion years ago salt water or fresh water?

On a related note: would we be able to drink the water that is on Europa?

**Tags:** mars, water
> **Comments:**
> **username_1**: Europa: https://astronomy.stackexchange.com/questions/40239/is-the-water-underneath-europas-ice-cap-potable  

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## 1 answers

### Answer by username_2 on 2022-03-13. Score: 13

The article ["Water Activity and the Challenge for Life on Early Mars"](https://www.science.org/doi/abs/10.1126/science.1155432) finds that the early Martian ocean would have been acidic and almost as salty as the dead sea.

The estimates for salinity of the Europan ocean vary widely, but most place the salinity [above 50 g/kg](https://www.sciencedirect.com/science/article/abs/pii/S0019103507000656), more than that of sea water (about 45 g/kg).

You couldn't drink it, but there are plenty of life forms that are adapted to this level of salt.

> **Comments:**
> **username_3**: `+1` but it's important to note that this is "educated speculation" rather than scientific fact or a widely held certainty. That there once was surface water now beyond reproach, but guesses about what the water was like exactly may evolve as more information becomes available. And as on Earth, since there was likely to have been rainfall and potentially less tidal mixing (no giant moon, further from the Sun), there could certainly have been a variety of different salinities rather than just one.  
> **username_3**: To that end I've just asked in Earthscience SE [How large were Mars' ocean tides and to what extent did they would keep the oceans mixing and tend to keep salinity uniform? Has this been modeled?](https://earthscience.stackexchange.com/q/23612/6031)  
> **username_4**: That said, you could purify the salty water to make it potable - something worth considering since it'd be easier to send desalination equipment than to send a large quantity of fresh water if there's enough usable water already there.  
> **username_2**: It's a little better than "speculation".  It is a peer-reviewed article published in *Science*, one of the world's top academic journals.  
> **username_3**: “Best-effort” scientific speculation or extrapolation from limited data can always be published in reputable journals as long as it’s presented as such, it gets the conversation started and provides methods and frameworks for further analysis. It also sends your citation count skyrocketing when it’s the first in a long series of papers that unfold when more data is available that might in fact support the opposite conclusion. I’ll take a look at the paper and see what’s there, but absolutely nothing wrong with deductive speculation.  
> **username_3**: My point is only that it’s *quite possible* this is wrong. I’m sure looking back through *Science* for articles about Earth’s surface 3.5 billion years ago we can also find plenty of wrong conclusions. Scientific research is always “best-effort” whether we say it like that or not.  
> **username_3**: and by coincidence to illustrate that point, this just showed up in google news feed: [Scientists propose a new mechanism by which oxygen may have first built up in the atmosphere](https://phys.org/news/2022-03-scientists-mechanism-oxygen-built-atmosphere.html) links to the *Nature Communications* paper [Oxidative metabolisms catalyzed Earth’s oxygenation](https://www.nature.com/articles/s41467-022-28996-0) Anyway still `+1` for the answer!  
> **username_5**: Yeah there does exist a spectrum for which something is "science" but still speculation. A lot of paleontology lives in this zone. We know what the bones look like, but we are taking the most educated guess we can as to what these extinct creatures looked like, and the science is in refining those guesses hoping some evidence shows up eventually that can settle the matter.  

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