Unsuitable conditions for life

[Svenito]

I've heard this on a science podcast (naked astronomy if I'm not mistaken) where it was said that planet X does not have the right conditions for life as its water contains too much salt.

I understand what they mean, but surely that's only the case for life as we know it. Is it not possible that an organism can evolve to survive in salty conditions, or conditions we currently think are unsuitable?

I am aware that there are certain limited number of building blocks for life across the entire universe, so I am sure there are conditions that are entirely unsuitable for all life, but I was just a bit surprised by the statement being so matter-of-fact. The arsenic based lifeform that was discovered not too long ago would be one example, or did was that something that was deemed possible, just not yet discovered?

Or perhaps I am wrong in assuming that life can evolve so diverse given that we all share the same laws of physics and the same set of chemical building blocks for life. 

[JulianO]

I think we'd need more information to discuss this more. What/where is planet X for instance, and how do they know it is so salty? 

There are lots of life adaptations, including halophiles, that do very well in salty environments (including the dead sea).

Life finds lots of tricks to live in inhospitable environments, and extra terrestrial life is an unknown quantity, but it would be wrong to rule anything out I think.

[Cath]

If their is one thing I'm learning from it all, that is to NOT take anything we come up with as being fact.

All that we like to think we know is based on what we have so far been presented with (by the universe), and on how much of what we are able to take in with our limited range of senses (biological or otherwise) and cognitive abilities, and also on how we decide to interpret what it is we are able to take in.

We know so little about life elsewhere Sven, infact, we know absolutely nothing about life elsewhere. Maybe try not to let what you hear to dishearten you, because we still have many many times more to learn than has so far been learnt.

We've only just begun to realize we even exist Sven. We are in no position what so ever to be deciding what can and cannot exist else where. Not to mention that any advanced life form could if they wanted too make anything possible, bend, tweak, twist any universal law (as we see it) etc. The only rules that exists are those that we ourselves are trying to create, which of course appears to be quite useful, if only to try and make sense of where we appear to be and how to maybe manipulate matter/energy to suit our current needs.

It doesn't pay to have a closed and/or limited mind when it comes to science.

[ollypenrice]

What are the essentials of physical life, I wonder? An ability to manipulate an energy source in order to do work? Anything else?

Olly

[Cath]

What are the essentials of physical life, I wonder? An ability to manipulate an energy source in order to do work? Anything else?

To maintain existence I guess?  Probably by way of rejuvenation/replication/reproduction in some way or other?

.

[JulianO]

A lot of people have tried to define what is life. Its pretty hard to pin down, but you usually know it when you see it!

Its interesting to attempt to match any characteristics you might define life with, to "fire". Fire comes out as alive in many definitions!

http://en.wikipedia.org/wiki/Life#Definitions

[Cath]

Fire comes out as alive in many definitions!

http://en.wikipedia.org/wiki/Life#Definitions

Indeed it does! which is quite fascinating really.

After all, we are Sun babies .. we really ort to take into account where we actually come from.

[Svenito]

I think it was a local body they had probed, but I cannot recall from memory, I am sorry. Clearly the level of salt will be a factor, but the question I was wondering about is whether it is ever wise to say "this cannot support life"

but yes, then we need to discuss what "life" is. 

Cath: I am pretty sure there is life out there somewhere. I know us being here is a huge coincidence and required a lot of things to happen by chance, and yet here we are. So given the number of other bodies out there, statistically something similar could have happened elsewhere. I was just a bit taken aback by the blanket statement of "this cannot support life because of these conditions", when the only life we know is the life we have here, which has evolved based on its environment as it is here on Earth. I just got to wondering if there really are conditions that mean there cannot categorically be any life.

[davew]

I'm no deep thinking scientist unfortunately, but I've been around long enough to realise one shouldn't let any facts get in the way of a good story   " Facts " are reported along the lines of Chinese whispers. If an Astro Biologist says some thing like " We believe from our studies that ( Put your favourite Planet or Moon in here ) is unlikely to be able to support life on the surface due to radiation damage of the chemicals and cell structures that would enable life to emerge and evolve. There may be the ability to remain below the surface so until we look we won't know "

How utterly boring. Lets shorten it to " We believe no life is possible on this Planet / Moon ". Not what was said but far more interesting. We are now in the enviable position to make things up as we go along. From that we can quickly get to " Scientists know nothing, therefor there must be life every where ".

There will be Astro Biologists spending their entire lives studying the possibility of life and they will have done experiments to see at what point " Life as we know it " breaks down. I have never EVER read any work that says life can't exist other than on this Planet. In trying to establish where it is believed life is most likely to exist, and maybe not, gives the opportunity to spend money wisely and not chase speculative dreams.

The statistics for life elsewhere are becoming overwhelming. The chances of intelligent life, pretty damn good.

Part of me hopes that Mars really is the source of Earth life ( As has been speculated ) so that those who constantly express the opinion that we are the runt of the Universe can hold a street party

Dave.

[ronin]

Is it not possible that an organism can evolve to survive in salty conditions, or conditions we currently think are unsuitable?

Well the simple answer to that is no, if it cannot get going in the first place owing to conditions then it cannot evolve to live in unsuitable conditions. You appear to be making the presumption that there is life there in some suitable conditions that are able to evolve to inhabit more unsuitable conditions.

Evolving to live in a hostile environment is different to life getting started there from a soup.

At this time just about everything we come with is total and utter guess work.

I suspect we are part of a somewhat unusual star and planetary system. How unusual I think we have yet to find out, even the "simple" idea that planets will be rocky close to the sun and gaseous further away appears very dubious now.  There was a high amount of agreement that that arrangement made complete sense, but it is wrong.

Even with our sun people forget that it is getting warmer, very slowly but it has no need to rush. In 1.5 billion years Earth will no longer be in the habitable zone, we will be too hot. However that means that a couple of billion years ago Mars was not in it as Mar's orbit was outside of it. How many keep saying life must have come from there and got a foothold here? The catch being Mars was outside the habitable zone for life for the majority of the solar history and is really just in it now.

[JamesF]

"salt" is a somewhat ambiguous term.  To a layman it might mean sodium chloride.  To a chemist it means (I think) any compound formed by reacting an acid with a base.  So how we should interpret the term "too salty" may well depend on the context in which it was being used at the time.  We have plenty of organisms living in our "salty" oceans and it may be that they would evolve to even more "salty" environments, but in an environment where there were high levels of transition metal salts perhaps it might be considerably more difficult.  I do fairly strongly believe that in many cases "life will find a way" however.

Obviously we can't meaningfully talk about what life we might find elsewhere in the universe that is completely outside our current understanding of what constitutes life in the first place.  We can look at what we believe is required for life as we do understand it to get some sort of baseline though.  We might say for example that to be considered alive an organism needs some way to be able to manipulate energy, or to create some sort of "energy" or "potential" gradient.  Perhaps the simplest way to achieve that is with liquid water molecules, though water is not the only simple compound that has a polar liquid molecule.  Ammonia might also fit the bill (from memory).  There may be other reasons ammonia wouldn't work, perhaps because of the unusual strength of nitrogen bonds.  I don't know.  It may be that there are more complex molecules that would be suitable, but Occam's Razor might perhaps suggest the simpler forms would be likely to occur first, or at least in addition.

In such a way it might be possible (probably has already been done, I imagine) to build up a list of simple criteria for there to be any chance of life existing as we understand it, starting with the presence of water in liquid form.  My understanding is that there aren't too many viable elements that could replace carbon in protein chains, so perhaps some form of carbon molecule that can be broken apart fairly easily should also be a requirement.  Perhaps it might be possible to evolve life without anything we'd recognise as a protein chain, but then it wouldn't be life as we understand it to be possible right now.

I think this entire area is absolutely fascinating.  If you look at the very basics of what we might consider to be life and then try to find some other way of achieving the same kind of process using different elements or simple molecules, there really aren't that many choices (which again isn't to say it couldn't be something totally different from anything we've ever encountered, but then we're back to recognising "life as we understand it").  It's also perhaps relevant to ask, if there is another way of doing it, why is it not present on our own planet?  Or has it been, and we just don't recognise it?  Perhaps life as we understand it is not the only form that works, but is by some measure the most efficient form that evolution has found and has outcompeted any others?

James

[JamesF]

A lot of people have tried to define what is life. Its pretty hard to pin down, but you usually know it when you see it!

Its interesting to attempt to match any characteristics you might define life with, to "fire". Fire comes out as alive in many definitions!

http://en.wikipedia.org/wiki/Life#Definitions

"Fire" seems to me to be a pretty nebulous concept in itself.  I'd never really thought about that.  Heat and flame seem comparatively easy concepts to define, but fire?  How would you go about defining "fire" to someone who had never experienced it in such a way that they'd recognise it if they saw it?

James

[Svenito]

ronin: Yes, perhaps evolve was not the best word to use to convey what I meant. I meant for life to form in different, or what we would deem, unsuitable environments. 

But reading what James read got me thinking that perhaps the life we have here is how it is because it's the easiest way to exist. Specifically the properties of the various compounds life on this planet metabolises. But then, if there's nothing else available, then whatever there is, ammonia or other, would be come the simplest thing to break down. I find the whole matter of what could be very interesting, and I totally accept that it's very speculative, as we cannot be certain what tricks nature has up its sleeve, but with a good knowledge of chemistry and physics, we must be able to get an idea what kinds of chemicals can be used by organisms and which cannot, or at least what combination of compounds must exist for the possibility of life. But then it's also a matter of other factors I guess, temperature, pressure, gravity etc, as I imagine everything will behave differently. So many variables....

By salt I think they meant the traditional NaCl btw

As for Mars, it's entirely possible that some rudimentary life form had a brief existence there before it couldn't manage to survive the conditions. I would assume it's entirely possible for planets to temporarily become hosts to a simple life form which may or may not make it through the next stages of evolution, or am I talking cobblers now?

Enjoying reading your thoughts