Lonely Life? – Is Earth the only planet with life in our galaxy?

[Jens]

Extraterrestrial fossils found in a meteorite? http://www.extremetech.com/extreme/150417-astrobiologists-discover-fossils-in-meteorite-fragments-confirming-extraterrestrial-life?

If this is true, I am wrong.

I will try to get the article. (Even though I am reading a lot of scientific books and original publications, I am not working as scientist anymore and have no free access -- but maybe google scholar helps)

 

However, first impression is not too good:

These findings aren’t a slam dunk, though. According to our in-house biologist John Hewitt, there’s a strong possibility that the fossils aren’t actually biological in nature — they simply look biological.

There’s also the fact that the research was published in the Journal of Cosmology, a peer-reviewed journal that has come under critical scrutiny numerous times since it was established in 2009. The journal faced a lot of controversy when it published a paper by NASA engineer Richard Hoover claiming to have found fossils “similar to cyanobacteria” in meteorites.

I add:

Diatoms are very complex protists (Eukarya). They appeared on Earth only about 200 million years ago. Like plants they have chloroplasts (which were initially coming from endiosymbiosis of cyanobacteria). As protists they are roughly a factor of 100 bigger in volume than bacteria or archaea. Such organisms have not been the source of of life (via panspermia) on Earth. They just have very hard cell walls containing silica (so this inorganic substance can also be made by living beeings).

Edited March 17, 2013 by Jens

[pwagen]

Extraterrestrial fossils found in a meteorite? http://www.extremetech.com/extreme/150417-astrobiologists-discover-fossils-in-meteorite-fragments-confirming-extraterrestrial-life?

From that article:

 

According to our in-house biologist John Hewitt, there’s a strong possibility that the fossils aren’t actually biological in nature — they simply look biological. “This is kind of like finding a Q from Scrabble floating in space; it may be worth 10 points, but finding a few Es first would be a bit more convincing,” Hewitt says.

 

Let's not go crazy here.

[Jens]

Extraterrestrial fossils found in a meteorite? http://www.extremetech.com/extreme/150417-astrobiologists-discover-fossils-in-meteorite-fragments-confirming-extraterrestrial-life?

I have read through the comments in your link: It is a kind of scientific hoax:

http://www.slate.com/blogs/bad_astronomy/2013/03/11/meteorite_life_claims_of_fossils_in_a_meteorite_are_still_wrong.html

 

So it is good to get some attention. But no science. No extraterrestrial life yet.

 

And yes: the quotes above where quotes from the web page itself and not from Gaylord. (I thought this was clear, sorry if that has caused confusion)

Thanks for providing the link Gaylord!

 

Edited March 17, 2013 by Jens

[Moontanman]

Actually, humans do very well support a much lower concentration of O₂, lower pressure and higher pressure, absence of N₂ and arbitrary concentrations of H₂O. Yes, I have seen avatar and I like the film very much (especially the plant life). However, it is not a scientific source of information . At the temperature range of liquid water, the possible molecules in the atmosphere is not endless, since molecules need to be small. Just assuming a planet with big oceans of liquid water, means that many other possible gases are washed out by rain to a large extend and will be used by microbial life as energy source. Microbes on earth have used and are still using basically any molecule as source of energy which is present in the environment (see for example "Brock - Biology of Microorganisms"). Like on Earth they will all be consumed (CO, SO₂, ...). Or those molecules are inert (like N₂), but this also means they are not toxic. So actually the molecule that will pose the biggest issue is CO₂. This is because of human blood pressure regulation. Even though it does not kill humans immediately you loose consciousness immediately. So for humans (unless genetically "improved" ) a planet is only suitable once it has reached the steady state we have on Earth today: A very low concentration of CO₂, because every surplus CO₂ has already been consumed by autotrophic life (like plants and cyanobacteria). So from my point of view a planet with liquid water and life will have an atmosphere like Earth over time.

 

Or which toxic molecule in the atmosphere you are thinking about?

 

 

What you state is very well explained in read "Rare Earth" (Ward D, Brownlee D (2000) Rare Earth. Why Complex Life is Uncommon in the Universe. ISBN 0-387-98701-0, Copernikus, Springer Press, New York.). I have read it. But I am not convinced.

 

As a biochemist looking at the exact details of life, I challenge the assumption of this book that abiogenesis is easy and the evolution from a first cell to a human (or any intelligent life form) is difficult (and I find this a bit human centric). Especially if we can explain the latter (evolution) but not yet the first (abiogenesis). From the biochemistry of life it is only a small step from a microorganism to a human but a big from chemical substances to the first microorganism. The space here is too short to list all the details that we (humans) share with all the existing life forms. However, of course I might be wrong.

 

But more to the facts: The book is completely underestimating the flexibility of life:

 

Temperature range: The only reason why there is no complex life above a certain temperature on Earth is simply because those habitats which are hot and wet do not exist or are simply too small, and not because complex life cannot survive above 50°C or so.

 

Stability: Let’s keep with the definition of the book that complex life is something like plants and animals. All animals suddenly appeared 800 million years ago, after a much longer time period, where only microorganisms were present. This time of 800 million years is the same time in which probably (still in discussion) Earth had a dramatic climatic shift and was completely frozen (snowball Earth). After 10 million years of a snowball so much CO2 accumulated in the atmosphere (because there was no rain any more) that the green-house effect over the equator was just enough to melt the ice there. This then resulted in a dramatic positive feedback (since free water absorbs the light and the heat) that Earth jumped from completely frozen to completely hot within 100 years. This means after those hundred years you suddenly had nice temperatures for life, and an enormous amount of cyanobacteria (still high CO₂) which serve as food for those Eukaryotes eating them. This means in such a paradise every cell was surviving, even if it contained a mutation that was not optimal. Surviving the accumulation of mutations that are each a disadvantage and only finally (with the last mutation) form an advantage, is critical to make big steps in evolution. Summary, if the environment is too stable, evolution quickly gets trapped in local optimums. So killing big amounts of life and so that life afterwards can colonize empty habitats with absence of stiff competition is what speeds up big evolutionary progress. And: Rapid climatic changes in east Africa is supposed to have triggered the emergence of homo sapiens. So more climate changes than we had on Earth actually means also quicker evolution. So there are good reasons to doubt that a giant moon is really needed. Changing rotation axis will not stop evolution, quite the opposite is true.

 

Do you have more details on the frequency or magnitude of those changes if there would be no moon?

 

 

The underlined text is a misconception many have, mutations by and large are neutral and have no effect. You were born with around 120 mutations (average for humans)

[Jens]

I might see if I can get a copy for myself. I was quite surprised to learn of the possibility that the "great oxygenation event" on the Earth could be shown to be due to this effect instead of biological production of over whelming amounts of oxygen through photosynthesis

 

I got the book "Unmasking Europa" a few days ago and read through the first 62 pages (out of 270). It is worth reading.

 

(off topic: Also the part showing from the authors point of view (Richard Greenberg) how big research projects are biased by humans which have to make their living and career in science. Of course I cannot judge, if he is right in some accusations, but what is described as humans frictions seems likely to be true, since this is just what you always see in huge organizations, no matter if it is business or science. ...and the author also states that the convervatism he is criticizing is definitely needed in some parts of big space projects -- so he tries to understand the other side.)

 

I share the authors (Richard Greenberg) wish to improve science independent on any personal interests (like research funding). Since I do earn my money in a field completely outside science and do this as hobby only I do not have to defend my position just to obtain more papers.

 

--> I have not reached yet the pages relevant to the critical biological part. I will do so over Easter holidays.

(sorry for being slow, but I only have a few hours for this per week left between work and family )

 

my text

Surviving the accumulation of mutations that are each a disadvantage and only finally (with the last mutation) form an advantage, is critical to make big steps in evolution.

The underlined text is a misconception many have, mutations by and large are neutral and have no effect. You were born with around 120 mutations (average for humans)

Yes. I agree.

 

What I meant goes one step further:

Sometimes for making bigger evolutionary steps forward multiple mutations (let's say 3) which have a real effect on the organism (and are not neutral with regards to phenotype) are actually needed at the same time. Since of course it is very unlikely that they all 3 happen the same time they happen sequentially and the intermediate organisms with only 1 or 2 of them need to survive. Evolution is typically rather quick if those intermediate steps are neutral (or even advantagous). However, if those intermediate steps are clearly not positive, the orgnisms will not survive enough generations to have a chance to make the last mutation needed, if there is strong competition. Strong competition you have if the organisms have already adapted quite well to a stable environment. This means evolution will be trapped in a local minimum and will not make bigger steps any more. This is the reason why typically the largest steps in evolution always happen, if organism can colonize a biotop without competition.

 

Example:

There seem to be evolution paths in which each small step form a slight advantage, so that you quickly obtain the same results: Transforming an air breathing terrestrial animal (a carnivor dinosaur or mamal) into nealry the same shape marine fish hunting animal like ichtyosaur and dolphine actually happend twice in evolution. Even though mamals had been there all the time of the dinosaurs, they never made it to dolphins as long as the dinosaurs where there. So of course competition often stops evolution from going certain paths. In this example the path from a air breathing animal to a quick air breathing marine fish-like looking animmal seems to be much simpler than the path from a fish taking oxygen out of water to to a fish taking oxaygen out of air. The fish-hunting fish are trapped in a local evolution optimum and they cannot go out of it, no matter if much more time is given. Before the time of the dinosaurs there had been dolphin-sized (and larger) fish-hunting fish in addition to the sharks. Marine dinosaurs and later the marine mamals have taken their places.

[Moontanman]

 

my text Yes. I agree.

 

What I meant goes one step further:

Sometimes for making bigger evolutionary steps forward multiple mutations (let's say 3) which have a real effect on the organism (and are not neutral with regards to phenotype) are actually needed at the same time. Since of course it is very unlikely that they all 3 happen the same time they happen sequentially and the intermediate organisms with only 1 or 2 of them need to survive. Evolution is typically rather quick if those intermediate steps are neutral (or even advantagous). However, if those intermediate steps are clearly not positive, the orgnisms will not survive enough generations to have a chance to make the last mutation needed, if there is strong competition. Strong competition you have if the organisms have already adapted quite well to a stable environment. This means evolution will be trapped in a local minimum and will not make bigger steps any more. This is the reason why typically the largest steps in evolution always happen, if organism can colonize a biotop without competition.

 

 

I'm not sure what you mean here, lets take humans as an example, if you could take a photo of every one of your direct ancestors, back several thousand generations at no point would you be able to say, here is where we became human and before that we were apes, the graduation is so slow that this would be impossible.

 

 

 

Example:

There seem to be evolution paths in which each small step form a slight advantage, so that you quickly obtain the same results: Transforming an air breathing terrestrial animal (a carnivor dinosaur or mamal) into nealry the same shape marine fish hunting animal like ichtyosaur and dolphine actually happend twice in evolution. Even though mamals had been there all the time of the dinosaurs, they never made it to dolphins as long as the dinosaurs where there. So of course competition often stops evolution from going certain paths. In this example the path from a air breathing animal to a quick air breathing marine fish-like looking animmal seems to be much simpler than the path from a fish taking oxygen out of water to to a fish taking oxaygen out of air. The fish-hunting fish are trapped in a local evolution optimum and they cannot go out of it, no matter if much more time is given. Before the time of the dinosaurs there had been dolphin-sized (and larger) fish-hunting fish in addition to the sharks. Marine dinosaurs and later the marine mamals have taken their places.

 

 

The same is true for whales or ichthyosaurs, or sea going crocodilians. BTW, there were no sea going dinosaurs we know of... unless you count penguins...

 

And the steps from water dwelling to land dwelling is quite well represented in the fossil record and we have fish today that can survive both ways, air breathing and water breathing...

 

And some reptiles have indeed re-evolved the ability to breath under water... turtles that breath through their anus...

 

http://wiki.answers.com/Q/Can_Turtles_breathe_through_their_butts

[Jens]

I have read the book "Unmasking Europa" from Richard Greenberg now.

 

(off topic: From my point of view it is a great book! The author has suffered from a scientific community that is very resistent to new views for many years, so that the scientific predecessor of this book and this book was is main way to get the story out. So he is directly attacking people. This makes the book a very good reading for everybody who has to make his/her decision to stay in research or better make a life outside the scientific community. Depending on your personal taste you might also find this disturbing. Of course he has a certain self confidence (as otherwise he would not have written the book) but in contrast to many other proffessors he is not only mentioning his group as a whole -- and thereby only himself -- but the different contributions of his students by name.)

 

From my point of view he clearly prooves that Europa has a relativly thin ice layer (1 km - 10 km), which is cracking on a regular basis so that the liquid water below is directly connected to the surface from time to time. Of course this makes Europa a much more probable place for life than if the ice layer was 20 km - 50 km thick and never opens up. And to my point of view he is right in his proposals to plan for example a mission to investigate the ridges instead of mission impossible to drill through kilometers of ice. (I will provide detailed comments on the chapter 17 "The Biosphere" tomorrow, this is more my terrain.)

[Jens]

This will be a longer post, but I think it is needed .
Richard Greenberg – like many others in astronomy – is setting a strange (from a scientific point of view) focus on animal-like life forms. This has become very common in astronomy missions, because of 3 reasons:
1) It is fascinating.
2) It is needed to get the big public money for those missions.
3) Ignoring microbiology.
I agree with the first 2 points. So I will try to give more insight on the third point:
Life is a chemical thing. There is no way to discuss abiogenesis without discussing chemistry. Here I consider only life forms based on carbon chemistry in a water environment. (There are good reasons to assume that this is the only way of life). No matter, at Europa there is plenty of water and there is carbon. To exist all life forms need an energy source, a carbon source and another substance to balance out the redox reactions done with the carbon source to transform the carbon source into bio-molecules as part of the life form. There are two main ways of obtaining the energy and the carbon: Either the life form is taking both from the inorganic environment (autotroph life forms) or from other life forms (heterotroph life forms), no matter if those other life forms are still living or dead (means you just take the molecules of them after they died). Of course heterotroph life forms cannot exist without autotroph life forms. For example: Every single bit of energy your brain or your muscles are consuming (or wasting) had initially been collected as sun light by cyanobacteria or their degenerated form – the chloroplasts in plants, no matter if you eat animals or plants. Of course heterotrophy life forms always form a smaller part of the overall life. And of course in the beginning the first life forms could only be autotroph or use organic material which was in the environment by chemical processes and not by biological processes. So even if live started by using organic substances out of the environment it will quickly use all them up and should become autotroph as soon as possible. So instead of speculating on crazy shapes and forms of giant animal-like and plant-like life forms real understanding comes from investigating the basis: The microbial autotrophic life.
In a simplified representation this means the chemical basis is the following (of course other atoms like N, P, S are also needed):

Autotrophic life:
CO₂ + H₂O + X_red + Energy --> Biomolecules + X_ox

Heterotrophic life:
Biomolecules + Y_ox --> CO₂ + H₂O + Energy + Y_red

X and Y can be any substance that can undergo a redox reaction. X and Y can be the same or differ. The energy in autotrophic life might simply come from the reaction of Xred to Xox or might come from another independent chemical reaction. In plants on Earth X_red is H₂O and X_ox is O₂ and energy comes from sunlight, in animals on Earth Y_ox is O₂ and Yred is H₂O.

Applying this to Europa:
What is the carbon source on Europa? CO₂ had been detected. So it seems it is like on Earth the carbon source. If there is still under-sea volcanism on Europa there is a constant input on new CO₂. Even though Europa is smaller than the Earth the tidal effects of Jupiter might had kept the inner core still as liquid magma. If this is not the case, there is most likely a huge (but fixed) amount of CO₂ in the giant ocean (150 km thickness). This carbon then has to be recycled between life forms competing for it.
How to do the redox reactions and how to get the energy? If CO₂ is the carbon source (like on Earth), life forms need to reduce it. Molecular oxygen (O₂) is not helping here, since it oxidizes other chemical substances and cannot at all reduce substances (it cannot act as X_red). So the main question is how to reduce CO₂ and not if O₂ is present or not. Without any autotrophic life forms there will be no animals that could consume the O₂ to do the reverse reaction of the autotrophic life forms. Sulfuric acid and the corresponding salts are present on Europa but this does not help, since they are also completely oxidized already and cannot reduce CO₂.
One source for reducing power is - like on Earth - photosynthesis. With the help of light power (otherwise it would be chemically impossible) the reducing electrons are torn out of water molecules (which are always easily available). A certain part from the light power can be used (like on Earth) to create chemical gradients as internal energy form to drive life. However, Europa is different from Earth:
- The distance from the Sun is 5 times bigger – means 25 times less sunlight then on Earth.
- Only few cracks (or none) are active at given point in time. Active means they are opening and closing in a daily cycle. So there is not much surface which receives light. (Note that organisms trapped in permanently frozen ice below the surface might receive sunlight, but will not have steady access to CO₂ and other substances (like phosphate or nitrogen salts) to grow in frozen ice.
- Like mentioned by Greenberg the uppermost thin layer of the water and ice is killing life, since Europa has nearly no protecting atmosphere and Jupiter is causing a lot of molecule breaking radiation to come in.
- Crushing in the daily closing cracks will anyhow kill all plant-like organisms.
- Greenberg is assuming a 1000:1 ratio depth of the crack versus width. So even assuming a 200:1 (if the cracks are more distant than 100 km), this means the liquid water is very much in the shadow, since it does not reach the top (water is heavier than ice).
- If data is correct, it took about 1000 million of years of evolution on sunny Earth before emergence of photosynthesis with H₂O as X_red, and probably half that time with other substances (H₂S) as X_red. If Europa was covered with ice for most of its existence, photosynthesis probably never have evolved on Europa.
- The biggest issue is that those organisms that are enough at the top of the 1-10 km deep crack to receive light will all be squeezed out on the surface (and not down to the ocean) at a daily basis (a day at Europe takes 85 hours). The biomass lost by this cannot be replaced quick enough with growth under so little light and so low temperatures.

So it does not seem to work out for photosynthetic autotrophic life forms on Europa.

Of Course, you can assume, that the life forms live for a short cycle of let’s say 100 days (since they repeatedly have fallen back into the crack after being squeezed out once a day) until they finally left at the outside. Then they have to wait about 1 million years until this piece of the surface has been recycled into the ocean. Of course this scenario also means that the top of the crack after the first day is filled with crushed ice and not with liquid water. I guess this does not seem very plausible.

But still there are possibilities for life on Europa. There are other possibilities for getting energy and for Xred on Europa. I will come to this next week.

[Airbrush]

Do you really care how common life, or especially intelligent life, is in the entire galaxy? The galaxy is a big place. I am only interested in Earth-like planets within about 100 light years. Beyond that is irrelevant.

[Mr Monkeybat]

You are assuming that Aliens would want to colonize planets in general much less the earth. It seems for more likely from the stand point of both resources and incompatibility of life forms from different planets that artificial space colonies would be the easiest and ultimate the most likely way aliens would colonize space. Gravity wells are quite possibly places to be avoided by aliens lloking to colonize...

 

The entire galaxy could be colonized by many different species of aliens, our own Star could house many different aliens in it's ort cloud kuiper belt areas. In fact stars with out planets but extensive asteroid belts similar to Vega might be the most desirable of stars.

 

There have reception of radio sources that closely resembled terrestrial military radars detected from space, they were transitory and originated from near the center of our galaxy. Because they were one time events they do not count as evidence but they are suggestive...

 

There is no evidence that the asteroid belt or other small planetoids like the moon has been strip mined. Nor do infra red telescopes detect any waste heat from machinery, habitats, or fusion reactors in the Kuiper belt or Ort cloud. The exponential growth of life in new habitats is an inherent feature of anything that can reproduce, so the forces natural selection will insure that any Von Nueman robots or warp faring civilization will consume all minerals resources in the galaxy within a few thousand to a million years. So either interstellar travel and controlled nuclear fusion power is close to impossible, or industrial civilizations have a frequency that is near or less than 1 per Milkyway sized galaxy.

 

What is so outdated about primordial soup theory? Electric arcs in in mock ups of Earths early atmosphere produce building blocks for organic chemicals. Just because these experiments where done a while ago does not discredit them.

 

Suppose we did find a way to create donuts out of 2 tonnes of negative mass and warp between stars, and we found nothing but sterile worlds like the OP or Fermi's paradox would predict. How long would it take for a sterile earth like planet or moon seeded with algae and plant life to become habitable.

 

If we are using films like Avatar as scientific resource did anyone else notice that the CO2 levels given for the planet in Prometheus where borderline breathable? They did not need those space suits or helmets just maybe the occasional use an oxygen line.

[Ophiolite]

Your version of the primordial soup is out dated and the idea never suggested that lightning struck a pol of water and created anything...

I beg to differ - a polite way of saying you are wrong.

 

Here is the relvant passage from Darwin's letter to Hooker in which the primordial soup makes its first appearance, admittedly without being called such.

 

"It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present. But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, - light, heat, electricity &c. present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter wd be instantly devoured, or absorbed, which would not have been the case before living creatures were formed."

 

What is Darwin's electricity if not lightning strikes?

[Moontanman]

I beg to differ - a polite way of saying you are wrong.

 

Here is the relvant passage from Darwin's letter to Hooker in which the primordial soup makes its first appearance, admittedly without being called such.

 

"It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present. But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, - light, heat, electricity &c. present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter wd be instantly devoured, or absorbed, which would not have been the case before living creatures were formed."

 

What is Darwin's electricity if not lightning strikes?

 

The lightning striking a pond and creating a cell is bogus, cloud to cloud and or cloud to ground strikes create some of the chemicals that form the dissolved contents of the pond.

 

This is the question my reply was for.

 

SamBridge, on 24 Feb 2013 - 15:51, said:Which scientifically we expect was something lie lightning strikes a pool of water containing complex chemicals. Those possible circumstances still exist on Earth. There's still the same chemicals in the oldest life form now, there's still lighting, life had 3.8 billion more years to spontaneously form on Earth again, and out of all that time it didn't.

The idea of a warm little pond being struck by lightning creating life is not the current scientific consensus...

[Ophiolite]

"the idea never suggested that lightning struck a pol of water and created anything... "

The argument is that lightning strikes could have created more complex chemicals on the route to life. Invoking lightning as an agent in the process is not foolish, or disregarded.

[Moontanman]

The argument is that lightning strikes could have created more complex chemicals on the route to life. Invoking lightning as an agent in the process is not foolish, or disregarded.

I don't think that was what was being suggested, I still read the assertion as lightning striking a pool of water created life. Read in the context of what he was suggesting in that a bolt of lightning could do the same thing now I stand by what I said...

[Jens]

The argument is that lightning strikes could have created more complex chemicals on the route to life. Invoking lightning as an agent in the process is not foolish, or disregarded.

 

Yes.

But I also agree to Moontanman.

In any case, it is not really important.

On early Earth (or any other planet which will end up with oceans of liquid water) you have plenty of chemical energy on the hot mineral surface and evaporating water locally provides all you need to create energy rich condensed molecules out of things like H2CO initially from asteroids (or even CO from Earth itself). I guess this will be quantitatively much more relevant than lightning.

 

Here is the relvant passage from Darwin's letter to Hooker in which the primordial soup makes its first appearance, admittedly without being called such.

 

"It is often said that all the conditions for the first production of a living organism are now present, which could ever have been present. But if (and oh what a big if) we could conceive in some warm little pond with all sorts of ammonia and phosphoric salts, - light, heat, electricity &c. present, that a protein compound was chemically formed, ready to undergo still more complex changes, at the present day such matter wd be instantly devoured, or absorbed, which would not have been the case before living creatures were formed."

 

I think we know a bit more in microbiology now. Abiogenesis is a complex multi-step process and will not just happen at once by a lightning into a pond. (of course - as you know - ribosoms will not be created at once by pure chance). The present life makes it impossible for this complex multi-step process to happen again in nature.

And of course I agree to the "and oh what a big if". If anybody could repeat abiogenesis my complete thesis (see first post of this topic) is wrong.

Thanks for the interesting Darwin quote.

(Off topic: I always appreciated your clever posts. I am currently ordering one of your book recommendations. ).

 

There is no evidence that the asteroid belt or other small planetoids like the moon has been strip mined. Nor do infra red telescopes detect any waste heat from machinery, habitats, or fusion reactors in the Kuiper belt or Ort cloud. The exponential growth of life in new habitats is an inherent feature of anything that can reproduce, so the forces natural selection will insure that any Von Nueman robots or warp faring civilization will consume all minerals resources in the galaxy within a few thousand to a million years. So either interstellar travel and controlled nuclear fusion power is close to impossible, or industrial civilizations have a frequency that is near or less than 1 per Milkyway sized galaxy.

 

Interesting. Even though this goes into the direction of my thesis, I still have some concerns:

How sensitive are our detectors?

Would we really be able to to detect them?

If the minerals are somehow the same in any habitable solar system, why should you (as an extraterrestrial) pick them up from another solar system instead of the one you are living in?

 

What is so outdated about primordial soup theory? Electric arcs in in mock ups of Earths early atmosphere produce building blocks for organic chemicals. Just because these experiments where done a while ago does not discredit them.

 

I recommend to have a look into a biochemistry book. Even if you take of everything optional from the simplest current life forms they are incredibly complex. Actually from a biochemistry point of view a human is in the same order of complexity than a "primitive" bacterion (actually there is no primitive life). Abiogenesis is the process of how to transform chemicals into a system which can evolve. After evolution has started everything is reasonable plausible. Currently we cannot explain abiogenesis (yet), even though a lot of progress has been made.

To make a comparison:

Let's pack a 100 billion of planet surfaces (to equal the bigger size of microrobots compared to chemicals) with metal pieces of all kinds, shake the whole thing add some random current and hope that a self-replicating robot comes out. You might tell me that's impossible. I agree. But this is how I feel about abiogenesis (since I am an expert in biochemistry). Of course I do not claim that there is some intelligent design (and this is not the topic here to discuss it!), I just want to say, we are still missing something. And abiogenesis looks really like an improbable event.

[Moontanman]

There is no evidence that the asteroid belt or other small planetoids like the moon has been strip mined. Nor do infra red telescopes detect any waste heat from machinery, habitats, or fusion reactors in the Kuiper belt or Ort cloud.

 

I'm not sure what you mean by lack of evidence that any asteroids have been mined, how many have we really looked at closely? Some odd groves and such have been seen on the few we have looked at closely. I have my doubts about the need to mine asteroids for metals, I suggest that advanced civilizations would use mostly carbon to build their structures not metals. I'm sure metals would be needed but we tend to think of metals as the main ingredient in anything large we build but carbon fibers and nanotubes are superior in almost all ways to metal in building large scale structures, in zero G this advantage would be greatly magnified.

 

Also even in the kuiper belt or ort cloud there would be some metals in the icy bodies, comets are not 100% ices...

 

The none detection of heat sources in the Ort Cloud or Kuiper bothers me as well but I have been told that so far we have not put a telescope into orbit sensitive to detect such small sources of heat. There is still the problem of the fermi paradox, why don't we detect their communications?

 

The exponential growth of life in new habitats is an inherent feature of anything that can reproduce, so the forces natural selection will insure that any Von Nueman robots or warp faring civilization will consume all minerals resources in the galaxy within a few thousand to a million years. So either interstellar travel and controlled nuclear fusion power is close to impossible, or industrial civilizations have a frequency that is near or less than 1 per Milkyway sized galaxy.

 

The power problem is valid, without a power source there can be no ort cloud colonies... I have my doubts that such civilizations would consume all resources before moving on, the resources we are talking about is a great deal more vast than what we are used to dealing with, the idea that a civilization could or would colonise every star system in the galaxy in a few million years is based on the old idea that they would colonise planets, the ort cloud offers a few orders of magnitude more space and resources.

 

 

 

I recommend to have a look into a biochemistry book. Even if you take of everything optional from the simplest current life forms they are incredibly complex. Actually from a biochemistry point of view a human is in the same order of complexity than a "primitive" bacterion (actually there is no primitive life). Abiogenesis is the process of how to transform chemicals into a system which can evolve. After evolution has started everything is reasonable plausible. Currently we cannot explain abiogenesis (yet), even though a lot of progress has been made.

To make a comparison:

Let's pack a 100 billion of planet surfaces (to equal the bigger size of microrobots compared to chemicals) with metal pieces of all kinds, shake the whole thing add some random current and hope that a self-replicating robot comes out. You might tell me that's impossible. I agree. But this is how I feel about abiogenesis (since I am an expert in biochemistry). Of course I do not claim that there is some intelligent design (and this is not the topic here to discuss it!), I just want to say, we are still missing something. And abiogenesis looks really like an improbable event.

You do realize this analogy fails completely don't you? Chemistry is not random, it is deterministic and some reactions will occur more often than others and some are impossible no matter how much time you give them.

[Jens]

You do realize this analogy fails completely don't you? Chemistry is not random, it is deterministic and some reactions will occur more often than others and some are impossible no matter how much time you give them.

O.k. You are right. That analogy was too simplistic. I will try to think of a better analogy. Mainly because of mineral catalysis you cannot compare it. Chemical systems can much easier produce positive feedback cycles (however, that is not enough for evolution to start). But there is also near random chemistry at high temperature condensation and to chain up macromelecules initially. Nevertheless, you are right. Maybe I better try to list what is all needed for evolution to start.

 

Back to potential life on Jupiter moon Europa

 

There are two main scenarios for the biochemistry on Europa:

A) The mantle of Europa is solid and there is no volcanism any more. This is because Europa is much smaller than Earth and volcanism should have stopped already long time ago.

B) The mantle of Europa is liquid and there is volcanism left. This is because the tidal forces of Jupiter keep the mantle liquid despite its small size.

 

In this post I will focus on scenario A:

 

Since photosynthesis does not seem to be plausible (see my last post about Europa in this topic), the main issue in this scenario is to find a substance which can be oxidized to balance out the reduction of CO₂.

Water (H₂O) on the surface of Europa which is under heavy bombardment of radiation can only be transformed into H₂O₂, O₂, O₃, H₂ and into the radicals OH, O₂^-, and H. H₂ and H are quickly lost in space due to the low gravity of Europa. The remaining molecules and radicals are all highly oxidizing. In principle H₂O₂ could also serve as reducing agent and be oxidized to O₂ but the reaction does not work in the wanted direction but the other way round:

2 H₂O₂ + CO₂ <-- 2 O₂ + H₂CO + H₂O (H₂CO as example for a reduced biomolecule)

The brown color on Europas surface around the cracks looks like Fe(OH)₃ - rust. This also means fully oxidized, but of course it can also be a crude mixture of anything.

Even if you assume that a lot of reduced carbon species (like H₂CO) were coming initially from meteorites this means in this scenario that life could gain energy by oxidizing them to CO₂. Oxidizing will happen with the help from the oxidizing substances coming into the ocean from the recycled surface (O₂, H₂O₂). Part of the reduced carbon species are used to build the organisms. This means the basis for life will continuously smaller and smaller. In such a scenario very likely there will be no life left any more, as soon as all the reduced carbon species have been transformed into CO₂.

So scenario A probably means there is no life left on Europa. (Of course only if there was any at all – which I doubt – see the initial post of this topic.)

Does anybody knows if the magnetic field of Jupiter bring in many free electrons from space to Europa? This could be the source of substance which can be oxidized. The free electrons can reduce Fe^+III to Fe^+II or reduce sulfur in sulfate. Reduced sulfur or reduced iron would solve the problem.

[Moontanman]

Actually it is the radiation from jupiter that creates much of the H2O2, it's is most prevalent on the side facing into it's orbit around jupiter, it's trailing face has much less H2O2. This would indicate to me that UV may not have as big an influence in Europa's acquisition of H2O2 as was first postulated.

 

It would seem that even on the Earth it comes down to volcanism, stop the flow of heat and the chemicals that are released by the heat and everything runs down to full stop... Wouldn't that be true if A is true?

 

Also if A is true I would expect Europa's ice to be quite thick and this alone would negate the idea of life...

 

If we can use Saturns moon Titan as a guide all may not be lost, Titan has volcanoes of water, wouldn't this indicate that gravitational heating may indeed be enough to assure B is the most likely scenario?

 

http://www.space.com/10486-ice-volcano-saturn-moon-titan.html

[Jens]

I'm not sure what you mean here, lets take humans as an example, if you could take a photo of every one of your direct ancestors, back several thousand generations at no point would you be able to say, here is where we became human and before that we were apes, the graduation is so slow that this would be impossible.

Yes, I fully agree. Of course I am not doubting evolution as a slow gradually process. And of course what is shown in some "science" fiction cinema films where you can watch evolution happening within some minutes (mainly as otherwise the film would be very boring and the film makers need to earn money) is complete nonsense (and you are right, if you argue against this). What I mean is a scientific concept. I will try to find different words:

 

Evolution is mutation and selection. Even though the mutations happen random and typically at roughly the same pace (since the reason for them is chemical statistical behaviour or radiation which is roughly constant), the selection part is of course heavy dependent on competition. And competition is not constant at all. So overall evolution over one long time period (let's say 100000 years) can be of much different speed than for another time period which is exactly as long.

 

More concrete:

If there is an opportunity for life or a life form (no matter if it is microbes or big animal life forms) to colonize an inviting habitat empty of competitors, there is for a longer time period no competition. So for many generations a given individual do not need to be really fit to have multiple descendants. This means for many generations a mutation which is not lethal but disadvantageous is not removed from the gene pool and many individuals are carrying it. Now imagine there is a certain feature (like photosynthesis using H2O instead of H2S as input) for which you need multiple proteins (lets say 5) to change simultaneously to function but all the changes alone are disadvantageous. Only in combination they provide a benefit. If there is stiff competition this will never happen, because the individuals with one or multiple of these mutations will die. So there is never an individual that has the chance to accumulate all five mutations. However, this looks completely different, if there is no or only little competition.

This is why from an archaeological view there are some time periods in which evolution made big "jumps" forward and others in which evolution was much slower. Note that "jump" here still means many ten-thousand years. Those time periods on a regular basis go in line with colonization of an habitat without much competition.

 

Or in genetics terms: The molecular clock of mutations is constant. The molecular clock of evolution (mutations forward, selection, mutation backwards, selection, ...) is not constant, since selection pressure is not constant.

[Jens]

Do you really care how common life, or especially intelligent life, is in the entire galaxy? The galaxy is a big place. I am only interested in Earth-like planets within about 100 light years. Beyond that is irrelevant.

Yes, I care about common life!

Actually for me life (in any form) is just incredible.

... and if it is only like bacteria, which are already very complex. There is nothing like primitive life left, especially if you look at the metabolism. Every microorganism left today which is capabable to survive wihtout eating other life forms or living from their remains, is even more complex in metabolism than animals. Of course animals have a much more elaborated regulation and structural features than bacteria. The basic machinery of life on Earth is the same for all life forms.

I gave reasons that any life is very rare (see the first original post).

I restricted the statement to our galaxy only for the reason to not have a dicussion about the infinite univers (which would be another topic).

 

Actually it is the radiation from jupiter that creates much of the H2O2, it's is most prevalent on the side facing into it's orbit around jupiter, it's trailing face has much less H2O2. This would indicate to me that UV may not have as big an influence in Europa's acquisition of H2O2 as was first postulated.

 

It would seem that even on the Earth it comes down to volcanism, stop the flow of heat and the chemicals that are released by the heat and everything runs down to full stop... Wouldn't that be true if A is true?

 

See my post on April 1st in this topic. On Earth life is now independent of scare reduced molecules from volcanism (thanks to photosysnthesis). However, it still needs CO₂ as a carbon source, which is constantly refilled in huge amounts by volcanos. If this would not happen, the carbon lost in the sediments would constantly decrease the amount of carbon available for life. So even though life is recycling carbon it would become less and less over time. (On Europa this is a bit less of an issue, since the giant ocean is probably full with huge amounts of CO₂.)

Without photosynthesis the critical thing for life is reduced substances (X_red) which can be used to take electrons to transfer them to CO₂ to make molecules of life out of CO₂. H₂O₂ can not act as such a substance.

The area (as distance form the center of gravity -- the sun or a big planet like Jupiter) where a planet or moon collects much H2O is always also the area where oxygen (as atom in any form) is quite abundant. The whole surface of Earth is full with fully oxidized chemicals -- like stones and water)

 

On Earth you had and still have multiple sources of X_red:

1. The initial load of carbon species coming from somewhere else (via meteorites.)
2. H₂, H₂S, S_8, COcoming from volcanos (I have to look for other reduced molecule species, but these are the main ones).
3. thanks to the energy of light life can also make the chemical impossible: to take electrons from abundant H2O and make itself independent from the rare other sources of X_red. This is called photosynthesis. However, photosynthesis is a rather complex thing, especially the final one taking the electrons from water. Life on Earth and nowhere else will start with photosynthesis.
4. maybe cracking of CO₂ or carbonates (the correspnsing salts) at very high temperature on the surface of molten rock. This might produce oxygen species and more reduced forms of carbon. I have to check this one out.

On Europa things look different:

Source 1 of course will not last forever (especially if it is shielded via the ice). As soon as life has oxidized it all (with the help of the H₂O₂ from the surface) it is finished with life.

Source 3 will not work, as I have pointed out above (in an earlier post at April 1st).

Volcanism is the only source (both behind source 2 and source 4) that I can see working at Europa. (At least from what I see by now).

Edited April 21, 2013 by Jens

[Jens]

To discuss the possibilities of life, it makes sense to consider the 3 main restrictions for life on a planet with water:

A: the carbon available to life

B: the energy available to life

C: the chemicals which can be used as electron source (to reduce CO₂)

 

This is roughly the situation on Earth (assuming the standard way of thinking that life started after time point 2. I doubt this -- see initial post of this topic.)

 

A1: High levels CO₂ and initial load carbon containing molecules of all kinds are available (e.g. all kinds of condensed forms of CH₂O like sugars)
A2: no changes
A3: Life has transformed the initial load carbon into biomass and some into CO₂ or CH₄, but there is still a huge amount of CO₂ available for life.
A4: Life can use carbon more efficiently by obtaining energy from light. A bit more CO₂ is transformed into biomass.
A5: Photosynthesis dramatically reduced the amount of CO₂ available. Today in some tropical regions CO₂ is already the limiting factor for some plants. However, for other regions and C4-plants light energy is still limiting and not CO₂. So overall energy is still the limiting factor.

B1: Energy is available as condensed phosphates (pyrophosphates) and other condensed molecules of all kinds that provide energy simply by hydrolysis. Those condensed molecules are formed in cooking and drying on hot rocks (no burning since there is no O₂) and are than transported by liquid water to other places as soon as the rock is covered with water again. In addition to the condensed molecules there is also chemicals produced as from volcanoes today: e.g. H₂ and H₂S which can produce energy during chemical reactions with other inorganic compounds.
B2: The condensed molecules have undergone (very slowly) spontaneous hydrolysis, so that much less is left.
B3: Life consumed all the remaining condensed molecules, so chemical energy becomes the limiting factor.
B4: Using light as energy source provides a dramatic extension of the potentially available energy for life.

C1: The initial load of carbon has all kinds of different oxidation states, so electrons can be re-arranged to produce biomass out of it (and CO₂ or CH₄ as end products). In addition there are reduced inorganic molecule species (like H₂S which can be used to reduce CO2. Those are provided constantly by volcanoes and have accumulated in the oceans.
C2: no changes (at least following standard assumptions that life emerged late)
C3: Only the inorganic molecules are left. The rest has been transformed into biomass. However, life needs more energy than reducing power, so the energy is the limiting factor.
C4: Using light energy but other molecules than water as electron source, makes the reduced molecules the limiting factor for still growing the biomass. And in addition some reduced molecules can be used which could not be used without light energy. But still life is dependent on volcanic activity.
C5: The final (and most complex) way of using light energy is the current photosynthesis in which the energy of multiple photons is added up to ultimately take electrons from water (which is available in ‘unlimited’ amounts) and produce O₂. So the electron source does not limit life any longer.

 

I will (in ~10 days) make a corresponding picture with an explanation for the case of Jupiters moon Europa (under the theoretical assumption that life emerged there, too) -- and discuss the situation.

[Gaylord]

Here's a new story about the importance of our moon.

http://news.discovery.com/earth/weather-extreme-events/blog-what-if-the-moon-disappeared-130425.htm#mkcpgn=emnws1

Our planet is rare in the extreme.

[Moontanman]

Here's a new story about the importance of our moon.

View full size image

 

These findings suggest that Mars was a protoplanet that escaped merging with its siblings.

However The Earth acquired its large Moon there can be no doubt conditions on the Earth would have been different but that doesn't mean life wouldn't have adapted to a different Earth and saying that the Earth would be different because because it would be different actually only indicates the Earth would be different... not lifeless...

[Mr Monkeybat]

Mars seems to of maintained a non extreme axial tilt despite the absence of a large moon. Although it no longer count as planet Pluto is another example of a body with a proportionally large moon, so much so I think it counts as a binary dwarf planet with an orbital point above Pluto's surface. A gas giant could have several earth sized moons, it would not not matter if they got tidally locked to the gas giant as the orbit of the gas giant would provide the day night cycle preventing the atmosphere freezing on one side.

[vampares]

The most likely planet is venus. It has a mass closest to that of earth. Mercury appears to not only look like the Earth's moon but it also seems to be weighted like it. This mercury may be venus's intended moon. It is not terribly far from capturing it.

 

It would seem the mass of venus is slightly less than that of earth.

 

Venus is covered with CO2 and sulfuric acid. This is the environment in which life could spring up. There has to be some atmosphere on the planet.

 

I think mars is just not a large enough body of mass to retain an atmosphere. The periodic table sort of dictates these things.