How could life on icy moons have started?

Gwynston

I read lot about the exciting possibly of liquid water below the surface of the likes of Enceladus, Titan, Europa etc. which could possibly support primitive microbial life.

The reasoning behind the theory is that life as we know it essentially just needs water and energy to survive. And extreme forms of microbial life exist in unimaginably harsh environments on Earth.

But the big difference is that life evolved on Earth in supposedly (more) favourable conditions first. It's only through billions of years of evolution that life has managed to migrate and survive in some of the harsh environments here.

Another ingredient needed to start life are organic molecules and the building blocks for amino acids, which I believe have been found floating about the solar system.

But just because the ingredients exist and just because life can survive in harsh environments, doesn't mean it can start there! Has anyone come up with a theory of how life could have actually started on these icy moons?

Chemical Byrne

Panspermia from meteorite impacts with earth after life had begun? But how would any surviving organisms get below the ice? That's a mark against panspermia.

Gwynston

Yes, I suppose conditions could have been different in the long past on these moons and life could have got a foothold via panspermia. But in all the articles I've come across discussing how life could exist in these places, I don't recall an explanation of how it could have plausibly started.

Maximus Alexander

Gwynston wrote: »

I read lot about the exciting possibly of liquid water below the surface of the likes of Enceladus, Titan, Europa etc. which could possibly support primitive microbial life.

The reasoning behind the theory is that life as we know it essentially just needs water and energy to survive. And extreme forms of microbial life exist in unimaginably harsh environments on Earth.

But the big difference is that life evolved on Earth in supposedly (more) favourable conditions first. It's only through billions of years of evolution that life has managed to migrate and survive in some of the harsh environments here.

Another ingredient needed to start life are organic molecules and the building blocks for amino acids, which I believe have been found floating about the solar system.

But just because the ingredients exist and just because life can survive in harsh environments, doesn't mean it can start there! Has anyone come up with a theory of how life could have actually started on these icy moons?

How are you defining a harsh environment when it comes to abiogenesis?

Hadean and Eoarchean Earth were not pleasant environments, and the environments on other solar system bodies would have been just as different back then as Earth's was.

Mickeroo

Chemical Byrne wrote: »

Panspermia from meteorite impacts with earth after life had begun? But how would any surviving organisms get below the ice? That's a mark against panspermia.

Unlike a rocky planey and ice planet could "heal" itself after an impact I would have thought? Large meteorite impact shatters or vapourises icy surface, surface refreezes after a while leaving no visible crater. just speculation on my part, I'm no physicist.

professore

Gwynston wrote: »

...

But the big difference is that life evolved on Earth in supposedly (more) favourable conditions first. It's only through billions of years of evolution that life has managed to migrate and survive in some of the harsh environments here.

...

The simplest life forms haven't changed much on Earth (think blue-green algae) for billions of years.

ps200306

Some of the oldest forms of life on earth are extremophiles. You have endoliths which can live inside the pores between grains of rocks, you have bacterial spores that are known to have survived and remained viable for forty million years, you have organisms that can not only survive but can reproduce while subjected to accelerations of 400,000 g. If we find life in other parts of our solar system, it's quite likely that it'll have originated on earth, the place where life seems to thrive the best as far as we know.

As for where it arose in the first place, we don't really have a clue, because we've basically no idea how life gets going. All these "building blocks of life" clichés that you hear about moons, comets, exoplanets, and nebulae, blithely skip over the fact that we haven't the first notion how they could give rise to even the simplest modern life forms. Assembly by chance can pretty much be ruled out as being in the realm of the miraculous, but any assumed primitive "scaffolding" on the way from non-life to life has not left us any clues as to the sequence of events.

I guess the most fascinating discovery would be a life form -- assuming we could discover and recognise it -- that bore no apparent relationship to terrestrial life. Perhaps a second example of emergent life would give us more of an idea of the general pathways involved.

_Tombstone_

Shadow Biosphere

Gwynston

ps200306 wrote: »

Some of the oldest forms of life on earth are extremophiles....
As for where it arose in the first place, we don't really have a clue...

Thanks, I guess that more or less answers my question.
Since we don't know how life started here, it's easy to surmise extremophiles similarly starting on Europa or wherever without having to justify it too much!

Gwynston

_Tombstone_ wrote: »

Shadow Biosphere

Interesting stuff!
Especially the mysterious, unexplained 'desert varnish'.