Europa or Enceladus

[Voyager275]

Which one do you think has the highest probability for life. I think Titan might have life but it wont be like anything we've ever seen.

[GreenWolf]

Any life we find outside of Earth is going to be unlike anything we've ever seen. That's kind of the definition of "alien".

Also, Europa is sitting nice and pretty in the middle of Jupiter's radiation belts. It's probably a sterile ball of ice.

Titan is where it's at.

[SargeRho]

It's unlikely any of the radiation reaches the bottom of its ocean, or even the surface of the ocean under the ice tbh.

I'm going to say neither: Ganymede.

[Kibble]

We'll probably find life almost anywhere if we look hard enough.

[Frida Space]

Titan reminds me of prebiotic Earth. Not that I've ever experienced prebiotic Earth myself. Nor Titan.

[smjjames]

It's unlikely any of the radiation reaches the bottom of its ocean, or even the surface of the ocean under the ice tbh.

I'm going to say neither: Ganymede.

Wouldn't a layer of ice many kilometers thick work pretty well as a radiation shield?

But yeah, if there is life there, it'll be 'not as we know it'. Probably the only similarity would be that it's carbon based, but even that isn't neccesarily a given.

[-Velocity-]

Any life we find outside of Earth is going to be unlike anything we've ever seen. That's kind of the definition of "alien".

Also, Europa is sitting nice and pretty in the middle of Jupiter's radiation belts. It's probably a sterile ball of ice.

Titan is where it's at.

Being right in the middle of Jupiter's radiation belts is irrelevant. Only the surface of Europa is bombarded by that radiation. The ocean is protected by something probably like 50 km of ice and probably has much less radiation that even the surface of the Earth does, as we're "only" protected by a magnetic field and a comparatively thin atmosphere, not 50 km of solid ice.

Additionally, I haven't seen it verified or not, but I do remember a paper suggesting that Europa's oceans could be oxygenated by Jupiter's radiation. If I remember correctly, the way it would work is that radiation would break down water ice into hydrogen and oxygen in the surface ice. Some millions of years later, the surface ice might get subducted into the ocean and melt, releasing the oxygen. So Jupiter's radiation could even be benefitual for Europan sea life. However, for all we know, oxygen impedes the genesis of life by oxidizing biological molecules before they can self-organize into something more complicated. So it's also possible that oxygen in Europa's oceans could keep Europa sterile! (Oxygen in Earth's atmosphere didn't exist until life produced it, so it was not present during the genesis of life on Earth.)

Also, you have no way of saying that life on Europa wouldn't resemble life on Earth. Life tends to seek optimal solutions, and as such, it seems highly possible that life on other planets could closely resemble life on Earth, especially at the cellular level, with the most major differences being different DNA bases or a different chirality of proteins.

Edited April 2, 2015 by |Velocity|

[lajoswinkler]

Radiation in gas giants' belts doesn't penetrate more than 10-20 metres of ice (and I was very generous here). 5.4 Sv/day = 0.225 Sv/h of protons and electrons. Compare with probably tens or hundreds of kilosieverts in spent fuel pools of fission reactor power plants where few metres of water shield freshly spent fuel's gamma radiation from workers.

Both should have liquid water and are squeezed by tidal forces. Enceladus is a dwarf compared to Europa, so I'd say pockets of water. Europa is huge and must have fluid underneath the ice cover. Chances are greater for Europa, IMHO.

Biochemistry of alien life is likely to be quite different than ours. Morphology and general organization not, as those are governed by simple laws of physics.

Edited April 2, 2015 by lajoswinkler

[AngelLestat]

Both had good chances.

Also, you have no way of saying that life on Europa wouldn't resemble life on Earth. Life tends to seek optimal solutions, and as such, it seems highly possible that life on other planets could closely resemble life on Earth, especially at the cellular level, with the most major differences being different DNA bases or a different chirality of proteins.

Yeah, that is a centralized point of view like we always had in the pass and we always discover how wrong we were.

[-Velocity-]

Both had good chances.

Yeah, that is a centralized point of view like we always had in the pass and we always discover how wrong we were.

There is a huge difference between saying "it's highly possible that" and "it's certain that". I stated the former, meaning I think it's important to keep an open mind, but that we should not be surprised at all if we find extraterrestrial life to be similar to life on Earth, because there's a good chance that it will be. It's so easy to say it will be different, but those people who say so have had a very hard time coming up with truly viable alternatives for even a substance as simple as water.

[lajoswinkler]

Yeah, that is a centralized point of view like we always had in the pass and we always discover how wrong we were.

At the contrary, we were usually right.

Life is seeking optimal solutions and basic morphology is tied to energy and matter balance. So cells will happen, as well as symmetries.

[Kryten]

Also, you have no way of saying that life on Europa wouldn't resemble life on Earth. Life tends to seek optimal solutions, and as such, it seems highly possible that life on other planets could closely resemble life on Earth, especially at the cellular level, with the most major differences being different DNA bases or a different chirality of proteins.

Given life on earth almost certainly didn't have DNA or proteins at all initially, I don't find this argument at all plausible, at least to the level you're suggesting. Life on earth is biochemically homogenous because of descent from a complex common ancestor, not convergence.

[AngelLestat]

At the contrary, we were usually right.

Life is seeking optimal solutions and basic morphology is tied to energy and matter balance. So cells will happen, as well as symmetries.

Kiryten was already very clear. But let me elaborate.

If we have a similar structure is because life was seed from a common place. You are right that life find always the optimal solutions, but only if this happen under the same enviroment. Look earth, almost the same enviroment and timeframe conditions but species are so so different from us.

In this case we are talking of a very different enviroment without any common ansestor (which we know).

Some examples of these error of thinking in the past:

-earth is the center of the solar system

-humans are not animals, we were created as an image of our creator.

-life cant exist without oxygen (one of the biggest dumb claim that I hear from scientist)

-Life exist in earth due the big coincidense of earth, if one is change it would not be possible... jupiter to stop comets, moon at the perfect distance, earth perfect distance to the sun, sun perfect distance to the center of the milky way... Those can be true if we take only the possibility to other creatures exactly like us.

-organic life only can derive from exactly the same compunds of our adn (later we find silice could produce life, also we discover than phosphorus can be remplaced by arsenic studyng bacteries from earth, etc

Every time we open our mouth to make a centered human claim we found how wrong we are not later on.

Life can exist in ways that we can not imagine, that is why we still have not a good definition of life.

But that is how our brain works, we can only make assumptions from the things we understand, the same than in the past we could understand the utility of fire only if someone else show us.

[Camacha]

But that is how our brain works, we can only make assumptions from the things we understand, the same than in the past we could understand the utility of fire only if someone else show us.

You are very right, life probably appears in ways we cannot even reasonably comprehend. Though, at the same time, you see the same solutions for similar problems again and again. Therefore it might be safe to say that life could very well look like Earth life, as the solutions to those problems will be the same on other planets. In a totally different set of circumstances though, who knows what will happen.

[lajoswinkler]

Kiryten was already very clear. But let me elaborate.

If we have a similar structure is because life was seed from a common place. You are right that life find always the optimal solutions, but only if this happen under the same enviroment. Look earth, almost the same enviroment and timeframe conditions but species are so so different from us.

In this case we are talking of a very different enviroment without any common ansestor (which we know).

Some examples of these error of thinking in the past:

-earth is the center of the solar system

-humans are not animals, we were created as an image of our creator.

-life cant exist without oxygen (one of the biggest dumb claim that I hear from scientist)

-Life exist in earth due the big coincidense of earth, if one is change it would not be possible... jupiter to stop comets, moon at the perfect distance, earth perfect distance to the sun, sun perfect distance to the center of the milky way... Those can be true if we take only the possibility to other creatures exactly like us.

-organic life only can derive from exactly the same compunds of our adn (later we find silice could produce life, also we discover than phosphorus can be remplaced by arsenic studyng bacteries from earth, etc

Every time we open our mouth to make a centered human claim we found how wrong we are not later on.

Life can exist in ways that we can not imagine, that is why we still have not a good definition of life.

But that is how our brain works, we can only make assumptions from the things we understand, the same than in the past we could understand the utility of fire only if someone else show us.

Those erroneous thoughts were not scientific, but religious or philosophical, so your arguments fails in its beginning.

Also, silicon based life has never been proven (and is also unsound, giving the poor capabilities of such molecules), and the whole arsenic genome bacteria thing was proven to be a case of faster mouths than brains. Check your sources.

[smjjames]

@people arguing: The problem is that we have a sample size of one to look at, Terran life, so we have no way of definitely finding out how life would operate until we FIND that life elsewhere. Simulations and theories are all good, but that's nothing compared to actually finding it.

[Bill Phil]

The problem with saying how life will be is like the problem of the theory of everythibg: Lack of DATA. Not the android, but empirical evidence.

Life is pretty well defined, actually...

[kerbiloid]

Thick ice → low radiation → low mutation speed → low evolution speed.

Small mass → weak or none tectonism → weak or none underwater chemicals emission → eternal checmical hunger → low evolution speed.

Thick ice → no light → no photosynthesis → eternal energy hunger→ low evolution speed.

Small planet diameter (both are 10x less than Earth) → small surface area (100x less than Earth) → 100 times less attempts for life to appear.

Both places are just two glass jars with a salty brine forgotten in a deep dark vault for billions years.

[Bill Phil]

Thick ice → low radiation → low mutation speed → low evolution speed.

Small mass → weak or none tectonism → weak or none underwater chemicals emission → eternal checmical hunger → low evolution speed.

Thick ice → no light → no photosynthesis → eternal energy hunger→ low evolution speed.

Small planet diameter (both are 10x less than Earth) → small surface area (100x less than Earth) → 100 times less attempts for life to appear.

Both places are just two glass jars with a salty brine forgotten in a deep dark vault for billions years.

Mutations are caused chemically, too. Look at viruses.

The mass of the body doesn't matter, it's the giant's mass that matters.

Europa could have a much larger volume of water, so, more attempts at life than Earth ever had.

[kerbiloid]

The mass of the body doesn't matter.

Europa could have a much larger volume of water, so, more attempts at life than Earth ever had.

Mass doesn't matter. Size does.

Life is concentrated not in a volume, but on an area.

Earth life: appeared on the surface of an ocean bottom (a thin layer with substrate and hot volcanic water),

evolved on the surface of an ocean (a thin layer whith the sunlight)

and currently lives on a land surface (a thin layer from tree roots to tree tops).

Large volume is just like a high ceiling of a room: pretty but mostly unuseful. Appartment area is important.

So, Europa and Enceladus oceans are like a 2x2 meters room with a 100 m ceiling.

Also, please don't forget the gravity. All edible things sink down to the bottom. Nothing to find 30 kilometers above.

Edited April 3, 2015 by kerbiloid

[Bill Phil]

Mass doesn't matter. Size does.

Life is concentrated not in a volume, but on an area.

Earth life: appeared on the surface of an ocean bottom (a thin layer with substrate and hot volcanic water),

evolved on the surface of an ocean (a thin layer whith the sunlight)

and currently lives on a land surface (a thin layer from tree roots to tree tops).

Large volume is just like a high ceiling of a room: pretty but mostly unuseful. Appartment area is important.

So, Europa and Enceladus oceans are like a 2x2 meters room with a 100 m ceiling.

Also, please don't forget the gravity. All edible things sink down to the bottom. Nothing to find 30 kilometers above.

Not entirely. Size and the mass of the parent body. This is actually really good for Europa, as its bigger and orbits a bigger and more massive giant.

Earth life appeared somewhere. We don't know where. There are plenty of hypotheses, though. But you are forgetting one fact... Things in water tend to make mixtures. This can make the solute not settle at the bottom. So, something'll stay up there, 30 km above.

[kerbiloid]

Size and the mass of the parent body. This is actually really good for Europa, as its bigger and orbits a bigger and more massive giant.

Sorry, I don't understand this.

Earth's parent body (Sun) is bigger than Europa's (Jupiter).

But how can the parent body mass effect Europa's ocean conditions?

(Except for tidal waves, which are also weak due to tidal lock).

Oh, got it. Probably you mean volcanic activity caused by Jupiter. All right.

Things in water tend to make mixtures. This can make the solute not settle at the bottom. So, something'll stay up there, 30 km above.

Earth ocean life has two resource generators:

- flat surface above: thin layer with photosynthesis,

- flat surface below: thin layer with volcanic boiling water carrying dissolved entities.

"Lite" things (mostly gases) float up from bottom to surface, "heavy" ones (organic waste) sink down from surface to bottom.

Mixtures and solutions are good but if something is solved in constant concentration that means it is not used as a food. Nobody eats NaCl or CaCO3.

And if you watch

https://www.google.ru/search?q=plankton+vertical+distribution&newwindow=1&tbm=isch&tbo=u&source=univ&sa=X&ei=xEceVeuuNsiXsAGoioToAw&ved=0CBwQsAQ&biw=1760&bih=881#newwindow=1&tbm=isch&q=plankton+vertical+distribution&nfpr=1

you can see that almost totally the Earth oceanic life is concentrated in the upper 100..200 meters of the ocean and it's no matter whether it is 100 m below or 100 km.

Europa ocean definitely cannot have the upper surface resource generator (because no light there), so the only place to get something edible is a thin layer near a bottom.

Large water volume is even worse here because it means that any organics will be diffused in low concentrations.

Edited April 3, 2015 by kerbiloid

[Bill Phil]

That video is talking about all types of life, right? Well, that just happens to be the layer that gets the most sunlight in the ocean, meaning that lots of photosynthesis happens there. Most life is in the oceans, and there's a lot in that area to eat thanks to all the photosynthetic lifeforms. It's a great place, all right. Turns out there is quite a lot of life there. But since there isn't one of those on Europa, and it has tidal heating throughout the moon, life can happen.

But if it has happened, it's probably prokaryotic or at best very early eukaryotic.

[kerbiloid]

Yes, it can.

And if this is so, the life will be concentrated where the sunken edibles and volcanic gases concentrations are max - i.e. at the bottom.

So the life distribution would be 2d (upon a surface), not 3d.

Earth surface is 100 times greater than Europa's one.

So, on Earth there were 100 more places for life to take a chance to appear - and a sunlight energy.

I.e. on Europa: maybe, if we're lucky, in several spots on the ocean bottom 50 km below the ice, we can find some strange micro-bubble colonies with chemical reaction cycles, primitive even if compare them to Earth bacteria.

[Bill Phil]

Yes, it can.

And if this is so, the life will be concentrated where the sunken edibles and volcanic gases concentrations are max - i.e. at the bottom.

So the life distribution would be 2d (upon a surface), not 3d.

Earth surface is 100 times greater than Europa's one.

So, on Earth there were 100 more places for life to take a chance to appear - and a sunlight energy.

I.e. on Europa: maybe, if we're lucky, in several spots on the ocean bottom 50 km below the ice, we can find some strange micro-bubble colonies with chemical reaction cycles, primitive even if compare them to Earth bacteria.

There is NO 2d at all in this universe. All objects are 3d.

Plus, you're using Europa's surface, not the sunken area.

All things would float down until they become buoyant. So, in the middle, in a nice three dimensional area.

There's not a hundred times more places for life to appear. You need to take into account all of the requirements of life. That limits you. Then, Europa and Earth are actually pretty equal. I mean, life had to form either in a hotspring or near geothermal vents. A heat source is very likely to have life if possible. Europa has a lot more water, and more sources of heat.

Life could not have formed on the solid surface of the earth (well, some kinds of life MIGHT, but not very many, as they come later on in history). That immediately removes almost 1/4 of your "100 times greater area" thing going on. Then you rule out places too cold.... And more of Europa's ocean is warm. They're pretty close. But, no photosynthesis could occur in Europa, it would have to be chemosynthesis. Which has happened on Earth.