Why Habitable Exoplanets Are Bad News

[Poor Richard Saunders]

We have to be open minded to all possibilities:

All alien civilizations happen to be using technologies unfamiliar to us;

Their EM footprint is simply undetectable;

The EM footprints are out there, we just haven't found them yet;

We are the only sentient life in the galaxy capable of technology.

Based on the size of the universe the least likely of those is probably the last one.

 

[Cypress]

Based on the size of the universe the least likely of those is probably the last one.

I limit it to our galaxy, because I don't see any conceivable way we could probe for life in other galaxies. It may, or may not be the case we are the only advanced sentient life in this galaxy, and I don't have enough information to say which scenario is more likely

 

[Saint Guinefort]

Because there isn't the tiniest, slightest piece of evidence that biological life can exist independently of carbon and water.

Guess that means that in the vastness of the entire universe you've saved everyone a LOT of time! Good for you! Now you can go sock-hunting with your buddy and best friend, Doc Douche.

That's more your speed.

 

[Cypress]

Because there isn't the tiniest, slightest piece of evidence that biological life can exist independently of carbon and water.

After four billion years of Earth history there was plenty of time and opportunities for silicon based or iron based biology to develop, but they never did.

Misconceptions of Science: Is Silicon-based Life Possible?

Is Silicon-Based Life Possible?
Why do people think that silicon-based life may be possible? The reason is simple. Silicon is below carbon on the periodic table and silicon can also make four bonds. So, it stands to reason, you could just as easily make complicated molecules with silicon. That makes perfect sense, except it’s not true. Why is that?

So, let’s contrast silicon and carbon. They can both form four bonds. On Earth, silicon is far, far, far more prevalent than carbon. Basically, silicon is found in sand and rock. In the Earth’s crust, silicon makes up 28%. Carbon, in contrast, is about 1,000 times less common. Yet carbon makes up life, while silicon doesn’t. If silicon were a contender, the fact that it is so common would give it a huge advantage.

So why does silicon fall short? Well, to begin with, when carbon makes four atomic bonds with all of its neighbors, the bonds tend to be of the same strength. In silicon, the first bond is much stronger than the others, which means the first bond is far more stable than the others.

It’s because the first bond is formed when the electrons from each atom reach directly to the other atom in a metaphorical handshake. The other bonds are formed from electrons that are further away and they effectively don’t get as good a grip.

Another thing is that when carbon connects with other chemicals common in organic molecules, the bonds are of similar strength. Carbon–carbon, carbon–oxygen, carbon–hydrogen, and carbon–nitrogen are all pretty similar. That means that, from an energy point of view, it is pretty easy to swap out atoms, which is the physicist’s way of saying that chemical reactions occur.

However, the silicon–oxygen bond is much stronger than say silicon–hydrogen, or silicon–carbon, or even silicon–silicon. That means that once silicon interacts with oxygen, it’s very hard to break them apart. This makes the ease and versatility of silicon chemical interactions far lower than the ones involving carbon.

And, about that silicon–oxygen bond compared to the carbon–oxygen one. When you breathe, you take in oxygen and breathe out carbon dioxide, which is given by the chemical formula CO2. The corresponding silicon molecule is SiO2 or silicon dioxide. The more common word for that chemical compound is ‘rock’.

Thus, a silicon-based creature using oxygen as part of its energy cycle would be breathing out sand. This isn’t a new realization. In 1934, science fiction author Stanley Weinbaum wrote a story in the pulp fiction magazine called Wonder Stories of an expedition to Mars. The astronaut encountered a life form that was gray, with one arm and a mouth that extruded bricks. He realized that the bricks were the product of the creature’s respiration.

So, while a simple understanding of the chemistry of carbon and silicon suggests that silicon-based life is possible, if you dig a bit deeper, it seems that silicon-based life isn’t really all that likely.


https://www.wondriumdaily.com/misconceptions-of-science-is-silicon-based-life-possible/

 

[Ross Dolan]

Because there isn't the tiniest, slightest piece of evidence that biological life can exist independently of carbon and water. After four billion years of Earth history there was plenty of time and opportunities for silicon based or iron based biology to develop, but they never did. And liquid water only exist under a narrow range of environmental conditions.

Once again, Cypress, you gotta be careful of that kind of "logic."

Keep in mind that there isn't the tiniest, slightest piece of evidence that biological life of any kind exists on the planets circling the nearest 25 star to Sol...

...but there is no way that leads to a conclusion that "therefore there is no biological life on any of those planets."

 

[Cypress]

Once again, Cypress, you gotta be careful of that kind of "logic."

Keep in mind that there isn't the tiniest, slightest piece of evidence that biological life of any kind exists on the planets circling the nearest 25 star to Sol...

...but there is no way that leads to a conclusion that "therefore there is no biological life on any of those planets."

We can't say for certain about any of this stuff, but we can make reasonable inferences.

Silicon is the second most abundant element on Earth.

Carbon isn't even in the top ten.

Is silicon-based biology was reasonably possible, it seems like four billion years of Earth history was plenty of time and opportunity for it to emerge.

 

[Ross Dolan]

We can't say for certain about any of this stuff, but we can make reasonable inferences.

Silicon is the second most abundant element on Earth.

Carbon isn't even in the top ten.

Is silicon-based biology was reasonably possible, it seems like four billion years of Earth history was plenty of time and opportunity for it to emerge.

I totally agree, Cypress.

BUT...conditions here may be markedly different from conditions elsewhere...and it is not impossible that somewhere, a silicone based life form is suggesting the improbability of carbon based life elsewhere because it has not developed there.

Not making a big thing of this...just adding what I consider a reasonable caveat.

 

[Cypress]

I totally agree, Cypress.

BUT...conditions here may be markedly different from conditions elsewhere...and it is not impossible that somewhere, a silicone based life form is suggesting the improbability of carbon based life elsewhere because it has not developed there.

Not making a big thing of this...just adding what I consider a reasonable caveat.

thanks

There is a huge range of environmental conditions here on earth, from superheated magma and hydrothermal systems, to the frozen cryosphere, to oxygenated rivers and lakes, to oxygen-free anaerobic bogs and soils.

But we still have never seen silicon-based biology.

That doesn't mean it's impossible. But it is reasonable to infer it is not seemingly likely

 

[Cancel 1 2023]

We can't say for certain about any of this stuff, but we can make reasonable inferences.

Silicon is the second most abundant element on Earth.

Carbon isn't even in the top ten.

Is silicon-based biology was reasonably possible, it seems like four billion years of Earth history was plenty of time and opportunity for it to emerge.

carbon based life is much easier. As noted earlier the bond enthalpies are more favorable and the options from self-catenation are fantastic.

There are whole host of alternative biochemistries based on things OTHER THAN Carbon. Boranes (for those places with reducing atmospheres), S-based life forms (S oligomers are usually linear rather than branched so it would lack the variety of Carbon, but is variety of bonds wholly necessary?) There are alternative solvents to water as well. NH3 for instance. H2S. Even HF in super weird conditions.

Given that we have almost ZERO data on any of these possibilities out in the larger universe it would be a bit hasty to simply dismiss them because OUR planet got to this type of atmosphere and conditions favoring this type of life.



I find it intersting how "militant atheistic" you are about alternative biochemistries but you are pretty willing to talk about all manner of religious and philosophical and metaphysical ideas across the spectrum.

Why are you so militant about this?

 

[Saint Guinefort]

thanks

There is a huge range of environmental conditions here on earth, from superheated magma and hydrothermal systems, to the frozen cryosphere, to oxygenated rivers and lakes, to oxygen-free anaerobic bogs and soils.

But we still have never seen silicon-based biology.

That doesn't mean it's impossible. But it is reasonable to infer it is not seemingly likely

How did you get your geology degree without any chemistry? Or did you do the bare minimum of Gen Chem 1 and 2?

 

[Dutch Uncle]

In recent years, I've been leaning towards the rare Earth hypothesis. Not only did a perfect storm of events create a stable, habitable Earth, but the jump from prebiotic chemicals to complex cellular life might be a result of an improbable and complex series of chemical steps which are only infrequently replicated elsewhere in the galaxy.

That would be one explanation. Less Doomsdayee than the "Great Filter"...even though mankind has come close to self-annihilation a few times in the past 100 years. There's also natural calamities such as an impact event we can't stop, a super volcano or plague. Had COVID-19 been 98% fatal, mankind would have survived, but quickly devolved socially back a few thousand years.

 

[Dutch Uncle]

How did you get your geology degree without any chemistry? Or did you do the bare minimum of Gen Chem 1 and 2?

How did you complete a PhD with a severe case of Rectal-Cranial Inversion Syndrome?

 

[Cypress]

That would be one explanation. Less Doomsdayee than the "Great Filter"...even though mankind has come close to self-annihilation a few times in the past 100 years. There's also natural calamities such as an impact event we can't stop, a super volcano or plague. Had COVID-19 been 98% fatal, mankind would have survived, but quickly devolved socially back a few thousand years.

Hopefully, we will find evidence of microbial life on Mars or one of the ocean moons in this solar system, or we will be able to scan exoplanet atmospheres for biosignatures..

It would be the scientific achievement of the millennium if that pans out.

On the other hand, if we keep finding sterile worlds, we will have to rethink the hypothesis that life is inevitable in the presence of liquid water and chemistry.

 

[Dutch Uncle]

Hopefully, we will find evidence of microbial life on Mars or one of the ocean moons in this solar system, or we will be able to scan exoplanet atmospheres for biosignatures..

It would be the scientific achievement of the millennium if that pans out.

On the other hand, if we keep finding sterile worlds, we will have to rethink the hypothesis that life is inevitable in the presence of liquid water and chemistry.

Agreed. While the building blocks are there, that tiny jump from inert to life seems to be consistently missing. At the moment, I tend to agree that, given the lack of evidence, life is extremely rare.

 

[Cancel 1 2023]

Agreed. While the building blocks are there, that tiny jump from inert to life seems to be consistently missing. At the moment, I tend to agree that, given the lack of evidence, life is extremely rare.

So you've sampled, what, about 0.000000000000000000000000000000000000000000000000000001% of the visible universe and you have drawn a conclusion based on that "evidence".

I'd say your sampling protocol might lead you to a Type II error.

 

[Cancel 1 2023]

Agreed. While the building blocks are there, that tiny jump from inert to life seems to be consistently missing. At the moment, I tend to agree that, given the lack of evidence, life is extremely rare.

It is almost like clockwork: you post, Cypress gives you a "thumbs up". Cypress posts and you give him a "thumbs up". Often times you two are the only two congratulating each other. Could you be bolstering your ego with a sock?

Sure looks like it.

 

[Cypress]

Agreed. While the building blocks are there, that tiny jump from inert to life seems to be consistently missing. At the moment, I tend to agree that, given the lack of evidence, life is extremely rare.

I haven't bought the sheer speculation about silicon life. It seems to be Star Trek that planted that in the public conciousness.

If silicon-based biology were reasonably possible, it seems like we should have seen it on Earth. The chemistry, time, and opportunity are all here. Silicon is far more abundant on Earth than carbon (by many orders of magnitude), Earth has a vast array of variable environmental conditions, and there have been four billion years of time for silicon biology to take root and propagate.

But we still don't see silicon-based biology.

 

[Dutch Uncle]

I haven't bought the sheer speculation about silicon life. It seems to be Star Trek that planted that in the public conciousness.

If silicon-based biology were reasonably possible, it seems like we should have seen it on Earth. The chemistry, time, and opportunity are all here. Silicon is far more abundant on Earth than carbon (by many orders of magnitude), Earth has a vast array of variable environmental conditions, and there have been four billion years of time for silicon biology to take root and propagate.

But we still don't see silicon-based biology.

I'd read that only carbon and silicon allow the chemical bonds that allow life, but understand that silicon life may not be on an interactive level like carbon-based life. It might be, literally, like talking to a tree instead of something as mobile and communicative as the Horta.

https://www.nbcnews.com/mach/science/silicon-based-life-may-be-more-just-science-fiction-n748266
Silicon-Based Life May Be More Than Just Science Fiction
Scientists are showing that nature can evolve to incorporate silicon into carbon-based molecules — the building blocks of life on Earth.

Now, scientists have for the first time shown that nature can evolve to incorporate silicon into carbon-based molecules, the building blocks of life on Earth....

...As for the implications these findings might have for alien chemistry on distant worlds, "my feeling is that if a human being can coax life to build bonds between silicon and carbon, nature can do it too," said the study's senior author Frances Arnold, a chemical engineer at the California Institute of Technology in Pasadena. The scientists detailed their findings recently in the journal Science.

Carbon is the backbone of every known biological molecule. Life on Earth is based on carbon, likely because each carbon atom can form bonds with up to four other atoms simultaneously. This quality makes carbon well-suited to form the long chains of molecules that serve as the basis for life as we know it, such as proteins and DNA....

...Carbon and silicon are chemically very similar in that silicon atoms can also each form bonds with up to four other atoms simultaneously. Moreover, silicon is one of the most common elements in the universe. For example, silicon makes up almost 30 percent of the mass of the Earth's crust and is roughly 150 times more abundant than carbon in the Earth's crust....

...After testing a variety of heme proteins, the scientists concentrated on one from Rhodothermus marinus, a bacterium from hot springs in Iceland. The heme protein in question, known as cytochrome c, normally shuttles electrons to other proteins in the microbe, but Arnold and her colleagues found that it could also generate low levels of organo-silicon compounds.

 

[Cypress]

I'd read that only carbon and silicon allow the chemical bonds that allow life, but understand that silicon life may not be on an interactive level like carbon-based life. It might be, literally, like talking to a tree instead of something as mobile and communicative as the Horta.

https://www.nbcnews.com/mach/science/silicon-based-life-may-be-more-just-science-fiction-n748266
Silicon-Based Life May Be More Than Just Science Fiction
Scientists are showing that nature can evolve to incorporate silicon into carbon-based molecules — the building blocks of life on Earth.

To me, the key words in that article were:

"However, there are no known natural instances of life on Earth combining silicon and carbon together into molecules."

Synthetically substituting Si for C in a molecule under controlled laboratory conditions is light years away from actual Si based life.

SI and C have some chemical similarities, but substantial differences too. Si is a metalloid, while C is a nonmetal; C is more reactive than Si; and C is capable of forming many more types of complex molecules and polymers than Si.

But the clincher for me is that we have never see Silicon-based biology anywhere on Earth, even though all the chemical ingredients, neccessary geologic time, and diverse thermal and chemical environments are all here

 

[Dutch Uncle]

To me, the key words in that article were:

"However, there are no known natural instances of life on Earth combining silicon and carbon together into molecules."

Synthetically substituting Si for C in a molecule under controlled laboratory conditions is light years away from actual Si based life.

SI and C have some chemical similarities, but substantial differences too. Si is a metalloid, while C is a nonmetal; C is more reactive than Si; and C is capable of forming many more types of complex molecules and polymers than Si.

But the clincher for me is that we have never see Silicon-based biology anywhere on Earth, even though all the chemical ingredients, neccessary geologic time, and diverse thermal and chemical environments are all here

Agreed it's artificial. Since we only have one example of life in the Universe, our set of examples is very limited. The fact scientists have shown it could possibly work is interesting, albeit not definitive. Similarly, we've found amino acids in meteors but no life.

Still, in a universe as large as ours, even if it's just one in a billionth chance, it's still a chance.