HotDayBreeze

Oh man! The fact that our current ocean isn't getting more salty implies that the addition by rivers is very significant to the total saltiness of the ocean! Over billions of years with no rivers, the ocean must get significantly fresher! Wow! That is strong confirmation that an entirely ocean world would at least be significantly less salty!

The presence of sodium and chlorine on the planet makes sense to me, but that doesn't necessarily mean it's dissolved in the water. I think the key understanding is if the water cycle is the key component of dissolving salt in water, or if the much less dramatic erosion on the bottom of the ocean is sufficient to make the water notably salty.

So far the best answer I've got is that water in comets and otherwise outside the planet might actually be something like salty, so maybe freshwater is just a temporary aberration of the water cycle.

At the same time, we know there are some processes that remove salt from oceans (e.g. the salt formations at the bottom of the Dead Sea), so in the end I think it would come down to where that balance of salt in vs salt out. It's not totally clear to me that without the continental influx of salt from rivers, that that balance would result in something like freshwater or saltwater. This thread has highlighted several factors that come in on both sides, so it may be something we won't know until we've explored more planets.

I feel like I'd rather drink saltwater before I drink water with ammonia dissolved in it.

Sure but once a continental plate is flooded, isn't it by definition an oceanic plate at that point? A continent only exists if it isn't flooded.

Thanks for all the detail! Your observation about comets is really pertinent. Saltwater is probably itself a purer form of water than comets. Maybe an ocean planet is actually more like a muddy swamp of nasty dirty water than a lake.

Exactly. If a planet ever had a salty ocean, adding more water probably wouldn't dilute it in any meaningful way, so it would need to be a planet that never had continents.

That is super interesting! I hope the Clipper gives us a definitive answer!

I was trying to figure out how much underwater erosion there is but if you compare the sandy and silty bottom of the ocean to like, Utah, it seems like continental erosion is orders of magnitude more significant.

Conversely, we know oceans deposit all sorts of stuff at their bottoms, which makes me think there is a small amount of salt being deposited. Would that cancel out significant underwater erosion?

Similarly, if underwater erosion was a big deal, wouldn't old lakes (in geological time) be notably saltier than young lakes? But the only salty lakes we have primarily lose all their water through evaporation, basically ultra concentrated river water.