How life got started in our solar system by Saibal Mitra

Thanks for your comments! There are indeed quite a few issues with my proposal that have yet to be worked out in more detail. But I gave a very general perspective on how to get to large biomolecules that can take part in interesting catalytic reactions.

I guess I could have explained things a bit better and in more detail. What happened was that two days before the deadline I took the bold step of ditching the essay I was working on and starting all over again with an essay on abiogenesis. Unfortunately, this has led to quite a few typos and badly written sentences in my essay (submitted about an hour before the deadline without proofreading).

Now, about the collisions, note that as pointed out in this recent article, the largest impacts that happened during the Late Heavy Bombardment period were an order of magnitude larger than previously thought. Impacts involving proto-planets that are, say, 250 km across are fiundamentally different than impacts involving 10 km diameter asteroid. In the latter case, very little of the debris escape the planet that is hit. In the latter case, not only will large amounts of the ejecta escape, a significant fraction of these will escape without having been significantly affected by the impact.

When pointing out just how large the KT impactor was, people will often say that when that asteroid hit Earth, the back side of it was still 10 km up in the air. But now picture this proto-planet hitting the Earth, when such a thing impacted the Earth in the LHB period, the back side would still be at the height were our low Earth orbit satellites are!

Then what happens is that the impact lasts 25 times longer than a KT-like impact, you'll then a get a lot more rebounding debris from the impactor that have not made contact with the Earth. While this is still a violent process, when it comes to transferral of microbes, there are far more opportunities compared to smaller impacts. One is then led to considering the transferal of microbes to Earth via fragments created by an impact on another body, say the Moon.

I'll read your essay; it may be interesting to make a list of all the essays on this topic, there are a few more I've seen but they can be hard to find among all the listed essays here.

One thing I should have explained better is the fundamental difference between my proposal and the current approach where you try to get to large molecules with interesting properties in some given environment at some uniform state (but not in thermal equilibrium; thermodynamically the creation of large molecules can be allowed, if a microbe could replicate there, then that means that the creation of a microbe lowers the Gibbs free energy, however the kinetics do not favor the creation of a microbe without a microbe being put in there from the start).

In the current approach the kinetics will keep the state of the system that initially contains only simple molecules in such a state with only simple molecules, the probability that something more interesting would appear is vanishingly small, and even if that were to happen, that fluctuation will just die down. Effectively, the state space of the system has an upper limit w.r.t. the complexity of the molecules that can be present. In my approach, there is no such upper limit. So, you're bound to stray into the real of extreme complexity. More is needed to explain how this leads to life, but should be clear that the approach is fundamentally different.

Jim, thanks for your comments. It sounds like your essay is going to be very interesting to read, I'll give you my comments as soon as I've read it.

The question of where these higher level phenomena like intent come from was skimmed over a bit, it's in the introduction. So, the issue is then that the laws of physics seems to lack a notion of intent. But there is, of course, no doubt that humans act with intent, and that humans are also subject to the laws of physics. One can then argue that what is going on here is that a living organism is a higher level system that, while instantiated by the laws of physics, is able to implement its own algorithm.

It's not all that different from saying that your computer does not violate the laws of physics and yet is able to run whatever algorithm fits in its memory, even if it looks like running some particular program would give the computer a property that doesn't seem to exist at the level of the fundamental laws of physics.

To be able to run some arbitrary algorithm requires the system to have enough control over its immediate environment, there will be feedback loops making sure the programmed commands are indeed executed. So, what must then happen is that information at the higher level where the system exists, feeds back to control the state at lower levels to make sure the system keeps on working. Walker and Davies that I've cited in the introduction have written quite a few papers on this topic.

Then what remains to be answered is how a system that isn't in such a state to begin with can start to exhibit such properties, so explaining how life started will automatically address the theme of the essay contest.

Lawrence and William, thank you both for your comments. I have seen Lawrence's essay a while back here, and I'll read William's essay as soon as I get the opportunity. It's interesting to address the essay theme from various starting points, William from the first cell, I tried to shed some lights on abiogenesis, but then Lawrence starts way at the beginning to explain why the universe is open, which is a crucial ingredient needed to make the universe habitable.

The word "life" in the title of the essay refers to microbes, basically the first lifeforms we know existed on Earth about 3.8 billion years ago. But, this cannot be the fundamental definition of life, defining life is part of the problem one has to tackle in order to explain how it arose (a point frequently made by researchers in this field).

George Ellis explains in his essay and in some of his other writings that top down causation is a key feature of living organism. Suppose e.g. that you are in a car, there is a red traffic light, you slow down your car to stop at that traffic light. Then because you consist of molecules, what happened should be describable in terms of the molecules you consist of.

Then apart from the sheer complexity making such an explanation not so practical, there is a more fundamental problem. If you trace down the processes at the molecular level that are involved in the chain of events in your brain that makes your brain give the command to hit the brake, that does not really provide for an explanation of why you decided to stop your car. It does not reproduce the higher level explanation in terms of you sticking to the traffic rules.

Now, it's still true that everything that happens must in principle be explainable from the molecular level, but you then need to go beyond a simple tracing down of some key triggers that caused the brain to hit the brake. You need to reproduce the algorithm that the brain is actually running, the traffic rules are encoded in that algorithm. So, in the end all you would be doing is using the information at the molecular level to establish the fact that it was a person who knows about the traffic rules who was sitting in the car, and from that it follows that the higher level explanation is valid. So, the molecular level explanation ended up giving the same reason for why you hit the brakes.

So, this then motivates defining life as a higher level system where the relevant information processing happens at that higher level. It is running algorithms that are only visible at that higher level. You may reduce it to its parts, but to understand why it did something you need to frame that in terms of the algorithms that are implemented.

Now, I take a different view. The algorithm itself, of course, didn't come into existence just out of thin air. So, a complete explanation involves explaining where the information that defines the algorithm ultimate originated from. So, there does exist in principle in a meaningful explanation in terms of fundamental physics concepts.

For life this means that I find the reverse of what I said at the start more appealing, i.e. an explanation of where what know is life (e.g. microbes) came from, will also provide for a definition of life. And then you are led to autocalytic processes. Now the people in favor of an algorithmic view at higher levels have made the point that there are trivial reproducing systems such as fire. But if you take a very deep look at such systems you'll find that it's not actually 100% trivial, a fire can only maintain itself and spread if there exists a region of stability. Compared to what we normally call "living organisms", it is indeed very trivial, but there are still feedback processes here that will make it going.

So, being alive or not is framing things in the wrong way, it's much more a matter of the degree to which some system is alive. And there then does exist a huge difference between a fire and a microbe. Also, there is exists a class of systems ranging from animals down to microbes and even simpler system such that the simplest of such systems could eventually give rise to all the of the other systems in that class. This may have involved a special environment like a proto-planet where you have both warm and cold environments as I've argued in my essay.

Dar Joe, I'll read your essay and give my comments on your essay page.

Dear Satyavarapu Naga Parameswara Gupta,

Thank you for you comments on my essay. I'll read your essay and give any comments I may have on your essay page.

Dear Jeff Schmitz,

Thank you for your comments. These processes in cold near vacuum conditions under the influence of radiation are very interesting. This recent article:

http://science.sciencemag.org/content/352/6282/208

reports on the synthesis of ribose from water, methanol, and ammonia exposed to UV radiation. So, I agree that such processes seem to be very important, you can't just have only a warm environment where life is ultimately going to take hold, because then the essential molecules won't get synthesized ab initio. I suspect that for quite a while when life is in the processes of developing in the warm environment, the processes in the cold environment will be essential to fill in the missing gaps of the biochemistry in the warm environment.

Dear Don,

Thank you for posting your comments here. Sloshing effects may play a role too, but you then need forces that don't uniformly accelerate the object. You can think about impacts, or strong tidal forces. Who knows, if there is life on Jupiter's moon Europa, such sloshing effects due to tidal forces may be important for the biology there.

I'll certainly take a look at your website!