Found this interesting so thought I would share. Seems we continue to find new lifeforms on this planet nearly everywhere we look. It's probably only a matter of time before we find life of some kind "out there."
Yeah, we keep finding out new conditions organisms can thrive in, which keeps expanding the environmental possibilities to look at in finding life on other spatial bodies. I think more than seeing which conditions we know organisms can thrive in we need to have a better understanding of what conditions can lead to abiogenesis. That, of course, doesn't diminish the awesomeness of finding life in new areas.
I'm certain the conditions to allow for life can't be all that rare - however, do we know how and why the first self-replicating chain replicated? From what I understand, that single trait could be statistically improbable enough to make life scarce.
It's getting clearer and clearer. Look up the work of Jack Szostak, he's one of the more prolific researchers in the field. At the moment I think there is a fairly solid idea of how the membranes formed and functioned and RNA as a candidate molecule for the beginnings of metabolism and heredity is becoming more and more viable. A plausible synthesis for most of the required organic molecules has been discovered. I don't know how much you want specific journal articles, but if you want some just ask and I'll post them in the thread.
Oh, I can also link to a nice video series on the subject over here.
Personally, I don't think the chain of events that occurred on early Earth is the only possible mechanism for the origin of life. Not based on the sheer diversity of life that actually is on the planet and of potential organic molecules.
Scarce? Probably. Non-existent? Not likely. Organic compounds are plentiful. If they exist on earth, they most probably exist everywhere. Most scientists agree that they were most likely delivered to Earth via comets and asteroids early in this planets formation and so would have been delivered to other bodies as well. Once they were here, it probably took only a static spark (lightning) to get the ball rolling, so to speak. And as we know, lightning is pretty much everywhere there is a heavy atmosphere. But that isn't the only thing that can conceivably start replication. Heat is another. And don't forget that Earth was a far different place when life is thought to have begun than it is today. So just because another spacial body doesn't have the conditions we have now doesn't mean conditions aren't right for abiogenesis to occur. We have recently found life on Earth that thrives on arsenic, which as you know is deadly to most life here. So why couldn't life develop elsewhere in conditions that are fatal to us?
Even in our own solar system, there are candidates for abiogenisis. One is the Saturnian moon Titan. Other than being extremely cold there, conditions are thought to be similar to those of Earth when life began. There are liquids there, rain, and, yes, lightning. It is not inconceivable that simple life forms could have already formed there.
Another strong candidate is the Jovian moon Europa. Again, cold as gee whiz on the surface and covered with a thick layer of ice, but lines in the ice are very similar to cracks in the ice in the Arctic region on Earth where it has opened up due to geothermal warming and then refrozen. This indicates a warm water ocean beneath the ice on Europa, probably heated by thermal vents like the ones in the OP of this thread. And if there is sufficient heat to crack open miles thick ice, there could possibly be enough heat close to the vents to spurn reactions in organic materials. Another Jovian moon, Callisto, also is thought to have an ocean that could harbor life.
Of course, this is not to say that life exists in these places, just that the possibility exists. And it will probably be a while yet before we can confirm it one way or the other. But I find the possibility exciting, fun to think about, and would like to think that we conclusively do find life (or that life has existed [Mars]) elsewhere before I die. But I'm in my mid fifties so they better get a move on.
We have recently found life on Earth that thrives on arsenic, which as you know is deadly to most life here.
No, it doesn't. That study was horribly flawed.
Call me an optimist, I realy do think that complex (ie; multi celular) life is common in the universe... Intelligence is rare, but armored worms grazing in herds under an alien sky, is pretty much a given.
The trick is getting life started on a gas giant.
I'm not disputing that there could be a million different combinations of variables that could sustain abiogenesis, just that any number of pre-life RNA or RNA-homologue molecule chains could come together on any number of worlds, but without that key ingredient that makes them self-replicate, it won't matter what its made of, or what environment it forms in, it won't become life.
I'm not really able to grasp everything I've been reading, but there's apparently several theories and no accepted answer to what the first self-replicating molecule or group of molecules was or what caused it to start doing this neat trick. I suppose that means the answer to my first question is a 'no'.
Like... chemistry? Life is, after all, just a complex chemical process.
Well that's the question, right? How common is it for that kind of molecule chain to spontaneously start replicating itself? And why does it start doing it when others don't?
Yeah, it's chemistry, but what's the process? I only took basic chem in HS so there's a lot I didn't learn.
She edited her post to include a video, a video from a series that I linked to earlier in the thread. Please watch it.
I did, I just am having a hard time following it after the bit about growing chains breaking up and forming new chains.
Let me consult a dictionary and get back to you.
Ok so... I'm hazy on thermodynamics, but if its an expression of energy does this mean it has to do with the attraction of atoms with unfilled electron shells to other atoms? I guess if it's that sort of chain reaction thing where the molecules will line up that way just because they're in the vicinity of each other, then it would be a constant occurrence as long as you have the right molecules.
The video doesn't explicitly say WHY they start replicating, which isn't too helpful for people with no science background, but I think I'm starting to work it out.
Okay, crash course in thermodynamics because I don't think working backwards from the current situation will work. I don't like to have to explain my explanations.
Thermodynamics is the study of energy, specifically heat, but it applies to other forms too. There are three laws within it. The first states that energy cannot be created or destroy, only changed. The second states that entropy of a closed system always increases. The third defines absolute zero.
Now, entropy (S) is often described as a measure of chaos. I don't personally like this definition because it is befuddling. Entropy is actually a form of waste. Entropy is energy that was used by a system, but cannot be harnessed by the system again. As a result of this perpetual motion machines are impossible. These laws provide the basis for the entirety of the field in the same manner that Newton's laws provide the basis for all of classical mechanics.
Another key concept I need to address is enthalpy (H). Enthalpy is what is used to measure the total energy of a given system. ∆H (delta H or change in H) is what we really care about and it tells us if a reaction is exothermic or endothermic. An exothermic reaction is one which releases heat and an endothermic reaction is one which takes heat from the environment.
Since we're discussing heat, I should probably also say what temperature (T) actually is. Molecules are always in motion, a model of which can be seen here. The higher the temperature, the more they move and the lower the temperature, the less they move. As a result, absolute zero is when there is no molecular motion, but this is a physical impossibility. Even so, absolute zero is a vital mathematical part of thermodynamics and essential for actually doing the equations.
Moving on, we get into some of the actual chemistry. Chemical reactions that are thermodynamically favored are reactions which are the most stable at a given energy level. The more energy (ie heat) there is in a system, the more unstable the configuration allowed. This is represented mathematically using Gibbs free energy (G), which measures the ability for non-mechanical work (very important in chemistry). This is able to tell us what reactions will occur because it helps us keep track of the energy involved. Specifically, we care about ∆G which is defined as ∆G=∆H-T∆S. As a result a change in enthalpy, temperature, or entropy will change the ∆G of a given reaction.
∆G is what tells us if a reaction is favored or not. A reaction is thermodynamically favored if ∆G is negative, it is unfavored if ∆G is negative, and it is at equilibrium if ∆G is 0. In this sense, favored means that the reaction is statistically likely to occur. For most purposes this means the reaction will happen. It is actually possible for a given molecule to react when ∆G is positive, but it will quickly react back to its original configuration. So, for the hypothetical reaction A → B we'll have something like one A molecule convert to one B molecule for every three B molecules that convert into A molecules (1:3 ration). At equilibrium it's a 1:1 ratio. If this reaction were favored we may see a 3:1 ratio.
This is where we hit upon something directly applicable for the video. There was a part about the cyclic motion of the protocells from a hot to a cold environment and back. The differing levels of heat give us a different ∆G for reactions and different reactions are favored. This is why under high temperatures the two polymer strands break apart from each other, but under lower temperatures a sister strand will polymerize. By itself, there is no self-replication, but due to the flow of current and the alternation of heat and cold there's a self-replicating polymer. Moving towards biology for the moment, any change which enhances the ability of this cycle will be evolutionarily favored.
We're not actually looking at the electron shells here, they are very important in chemistry, but they merely give us the possible reactions without telling us the probable reactions. Thermodynamics is what tells which of these possibilities will occur.
It's gonna take me a while to work my way through this. I'm not ignoring your reply.
Thanks, though, for explaining it in a simpler way than the brain-aching articles I've looked at... My ignorance isn't for lack of trying.