
Are planets with oceans common in the galaxy? It's likely, NASA scientists find - pseudolus
https://phys.org/news/2020-06-planets-oceans-common-galaxy-nasa.html
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noetic_techy
I really think prioritizing a subsurface mission to Europa's ocean should be
the primary focus. If life does exist under the subsurface ice it will be the
biggest discovery in history. Even if it doesn't, the exploration of an off-
world ocean will be huge.

~~~
NortySpock
It would be quicker and easier to sample the vapor plumes coming from cracks
in the ice shell of Europa. That would have organic compounds and possibly
even detectable bacteria. I'm hoping Europa Clipper has this capability.

On a different note, I did once write a short fiction story attempting to view
the world from the perspective of a ocean-dweller in Europa. Soft sci-fi
(universal translator) and all in good fun, but maybe someone will find it
interesting.

[https://www.reddit.com/r/HFY/comments/81jgky/oc_the_icy_heig...](https://www.reddit.com/r/HFY/comments/81jgky/oc_the_icy_heights/)

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andy_ppp
How can we be so certain the chemistry for life will be the same on these
distant worlds?

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bluGill
Chemistry places limits on what is possible. Water is a common and powerful
catalyst, it is unlike any life can exits without it just because so many
useful reactions happen only in water. (this discounts other catalysts mostly
because they are not as common as water). Carbon forms long chains with single
or double bonds (also triple bonds but they tend to be unstable) in ways that
no other atom will. Note too that water and carbon are extremely common, so
even if something else is possible you are then playing the odds that it is
common enough.

I'm sure a real chemists can place other limits on what is possible.

~~~
akiselev
Not a real chemist but my understanding is that there is no other solvent with
all of water's properties - cohesion, adhesion, high specific heat, pH
neutrality, polarity, density (in solid and liquid form), and reactivity - no
matter how rare. It is the only "universal solvent" (for polar molecules). In
order to imagine other forms of life, you'd have to make the jump from carbon
to silicon based life forms. Unfortunately, the energies involved in the
chemical bonds would mean that the reactions leading to self replicating
molecules would have to happen at very high temperatures or densities which
seem to make any life form extremely unlikely. Theoretically catalysts could
lower the reaction thresholds enough for life to take hold, but it's an open
question how such complex catalysts (enzymes) would emerge while bootstrapping
replication. Earth went through just the right series of steps and until the
planet cooled down, "stuff" just didn't stay in one place long enough to react
and form big molecules.

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cmrdporcupine
Biochemist Nick Lane espouses the 'alkalkine thermal vent' theory of
abiogenesis and believes that single celled prokaryotic type life is almost
inevitable on any planet that has or has had a mildly acidic ocean and active
plate tectonics with aklaline thermal vents. It's a pretty convincing theory.

_Complex_ cellular life (eukaryotic) is another story entirely. There's no
reason to believe they progress inevitably from bacteria. Bacteria have been
happily doing their thing without much change for the last 3.5 billion (or
more) years. The development of eukaryotes seems like mostly a fluke, and they
are very young in evolutionary history. And weird. Very weird.

[https://www.youtube.com/watch?v=gLcWfecmZhE](https://www.youtube.com/watch?v=gLcWfecmZhE)

~~~
perl4ever
It's one thing to say that a particular evolutionary step is a zillion-to-one
fluke and another to say that the possibility of _any_ fluke leading to more
complex life is of similar probability.

Maybe there are or will be found to be more weird hybrids in nature? I vaguely
recall reading something about how someone found a hint that brain cell
communication may have mechanisms that resemble viruses (and/or prions).

If you don't see eukaryotes as inevitable, then what about brains? Social
insects? What about human civilization? Biotechnology? I don't think it
contributes a lot to declare they _are_ inevitable, but I don't see why
eukaryotes would be a singular example of increasing organization that's
different from all the others. Zooming out, it seems like a lot of random
events merge into an exponential curve.

~~~
cmrdporcupine
The argument is basically from the fact that it occurred once and never again.
Eukaryotes are the result of a symobiosis between archaea and bacteria, and we
have yet to find any intermediary steps nor anything else that looks like a
similar occurrence in nature. And yet there's nothing stopping that fact from
happening again and it hasn't. Though apparently there is one tantalyzing find
that may or may not amount to something.

And also it seems to have taken 2 billion or more years for it to happen.

And bacteria and archaea are pretty much "happy" the way they are.

The development of eukaryotes broke an energy and complexity limit because of
the symbiosis between mitochondria (which were once free roaming bacteria) and
the host cell. It freed up the host cell to create genetic complexity orders
of magnitudes higher than what a prokaryote can produce. Complex life cannot
develop from prokaryotes because they simply can't produce enough energy to
make it happen.

Nor do they need to, they are extremely successful.

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gbrown
> And yet there's nothing stopping that fact from happening again and it
> hasn't.

This doesn't quite ring true, since the environment which a new Eukaryotalike
would have to compete in is a lot different now, since there are lots of
Eukaryotes around to eat its lunch.

~~~
cmrdporcupine
Nick Lane has a rebuttal to that, but I don't recall what it is off the top of
my head. His books are worth a read.

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ncmncm
If goldielocks-zone planets are common, but the ones with a large moon are
not, it might not matter that they start out with oceans if they turn into
Venus too quickly.

As I understand it, Earth is not like Venus in large part because the moon has
kept tidal friction from nearly halting its rotation. Rotation might be
necessary for tectonic activity, and tectonic activity for various other
essential processes. Rotation might be necessary to maintain reasonable
temperature or weather.

Earth's moon is considered a very rare fluke. If one in a million earths has a
serviceable moon, that might cut the odds of eukaryotic life enough to make us
unique in the galaxy.

Unless there are other fertile circumstances.

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neillyons
There is a good book on this called Alien Ocean.
[https://www.amazon.com/Alien-Oceans-Search-Depths-
Space/dp/0...](https://www.amazon.com/Alien-Oceans-Search-Depths-
Space/dp/0691179514)

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aiyodev
We keep proving factors in the Drake equation are much higher than predicted.
Maybe life isn’t precarious at all but civilization is.

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rbanffy
Well... We really need to figure out FTL travel...

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vasama
If time travel was possible, don't you think a time traveler would have
traveled back in time to give us time travel?

~~~
blackrock
Isn’t it obvious?

Maybe the time traveler’s grandfather got killed in a temporal suicide attack?
Thus preventing the time traveler from being born. Thus why we don’t yet have
time travel.

