Exoplanets and the likelyhood/unlikelyhood of life:

[beecee]

https://phys.org/news/2018-08-scientists-exoplanets-life-earth.html

the paper:

http://advances.sciencemag.org/content/4/8/eaar3302

The origin of RNA precursors on exoplanets

Abstract

Given that the macromolecular building blocks of life were likely produced photochemically in the presence of ultraviolet (UV) light, we identify some general constraints on which stars produce sufficient UV for this photochemistry. We estimate how much light is needed for the UV photochemistry by experimentally measuring the rate constant for the UV chemistry (“light chemistry”, needed for prebiotic synthesis) versus the rate constants for the bimolecular reactions that happen in the absence of the UV light (“dark chemistry”). We make these measurements for representative photochemical reactions involving  and HS⁻. By balancing the rates for the light and dark chemistry, we delineate the “abiogenesis zones” around stars of different stellar types based on whether their UV fluxes are sufficient for building up this macromolecular prebiotic inventory. We find that the  light chemistry is rapid enough to build up the prebiotic inventory for stars hotter than K5 (4400 K). We show how the abiogenesis zone overlaps with the liquid water habitable zone. Stars cooler than K5 may also drive the formation of these building blocks if they are very active. The HS⁻ light chemistry is too slow to work even for early Earth.

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My question/statement concerns the last paragraph from the article.....

extract:

According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. "Getting some idea of what fraction have been, or might be, primed for life fascinates me," said Sutherland. "Of course, being primed for life is not everything and we still don't know how likely the origin of life is, even given favourable circumstances—if it's really unlikely then we might be alone, but if not, we may have company."

OK, 700 million trillion, a large number by anyone's definition. So how likely or unlikely are the chances of abiogenisis? I have always  been of the opinion that given the large astronomical numbers involved, and the stuff of life being everywhere we look, that it is far more likely than unlikely. In fact I have stated many times that if the examples of life we have were confined to this fart arse little blue orb, it would raise far many more questions then any knowledge/evidence leading to a positive answer.

Let me give my own unsupported "guess work"estimates re life elsewhere. NOTE: Estimates purposely slanted towards a negative aspect.

Basic bacterial microbial life > 99%

More complicated life forms such as plants, > 50%

Basic Animal life forms > 5%

Advanced life forms analogous to humans > 0.1%

What do others think.believe?

[Moontanman]

25 minutes ago, beecee said:

https://phys.org/news/2018-08-scientists-exoplanets-life-earth.html

the paper:

http://advances.sciencemag.org/content/4/8/eaar3302

The origin of RNA precursors on exoplanets

Abstract

Given that the macromolecular building blocks of life were likely produced photochemically in the presence of ultraviolet (UV) light, we identify some general constraints on which stars produce sufficient UV for this photochemistry. We estimate how much light is needed for the UV photochemistry by experimentally measuring the rate constant for the UV chemistry (“light chemistry”, needed for prebiotic synthesis) versus the rate constants for the bimolecular reactions that happen in the absence of the UV light (“dark chemistry”). We make these measurements for representative photochemical reactions involving  and HS⁻. By balancing the rates for the light and dark chemistry, we delineate the “abiogenesis zones” around stars of different stellar types based on whether their UV fluxes are sufficient for building up this macromolecular prebiotic inventory. We find that the  light chemistry is rapid enough to build up the prebiotic inventory for stars hotter than K5 (4400 K). We show how the abiogenesis zone overlaps with the liquid water habitable zone. Stars cooler than K5 may also drive the formation of these building blocks if they are very active. The HS⁻ light chemistry is too slow to work even for early Earth.

<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

My question/statement concerns the last paragraph from the article.....

extract:

According to recent estimates, there are as many as 700 million trillion terrestrial planets in the observable universe. "Getting some idea of what fraction have been, or might be, primed for life fascinates me," said Sutherland. "Of course, being primed for life is not everything and we still don't know how likely the origin of life is, even given favourable circumstances—if it's really unlikely then we might be alone, but if not, we may have company."

OK, 700 million trillion, a large number by anyone's definition. So how likely or unlikely are the chances of abiogenisis? I have always  been of the opinion that given the large astronomical numbers involved, and the stuff of life being everywhere we look, that it is far more likely than unlikely. In fact I have stated many times that if the examples of life we have were confined to this fart arse little blue orb, it would raise far many more questions then any knowledge/evidence leading to a positive answer.

Let me give my own unsupported "guess work"estimates re life elsewhere. NOTE: Estimates purposely slanted towards a negative aspect.

Basic bacterial microbial life > 99%

More complicated life forms such as plants, > 50%

Basic Animal life forms > 5%

Advanced life forms analogous to humans > 0.1%

What do others think.believe?

.1% would mean tens of thousands of civilizations just in our galaxy wouldn't it? 

[beecee]

5 minutes ago, Moontanman said:

.1% would mean tens of thousands of civilizations just in our galaxy wouldn't it? 

Exactly!  I was waiting for someone to do the maths.  Let's though be even more conservative.....human or advanced lifeforms...> 0.001% 

 

My question/s [which obviously after checking I didn't make clear in the OP]  again though is "if it's really unlikely then we might be alone, but if not, we may have company."          [1] Wouldn't it raise far many more questions if we were alone?    and [2] While accepting the premise of searching for life where we already have evidence it could arise as being favourable in the first instance, other possibilities and chances may exist with stars at different stages of their development/life. 

 

 

[Moontanman]

1 minute ago, beecee said:

Exactly!  I was waiting for someone to do the maths.  Let's though be even more conservative.....human or advanced lifeforms...> 0.001% 

 

My question/s [which obviously after checking I didn't make clear in the OP]  again though is "if it's really unlikely then we might be alone, but if not, we may have company."          [1] Wouldn't it raise far many more questions if we were alone?    and [2] While accepting the premise of searching for life where we already have evidence it could arise as being favourable in the first instance, other possibilities and chances may exist with stars at different stages of their development/life. 

 

 

We are still talking thousands if my math is correct, Isn't 0.001% 1 in 10,000? 

[beecee]

Obviously it goes without saying, that if we were to find signs of basic bacterial/microbial life in our own solar system, that chances of life even beyond and at all stages, would be significantly increased.

[Moontanman]

3 minutes ago, beecee said:

Obviously it goes without saying, that if we were to find signs of basic bacterial/microbial life in our own solar system, that chances of life even beyond and at all stages, would be significantly increased.

 

Agreed, if we do find a second genesis of life in our solar system it says a lot about the general inevitability of life. Even if only one in a billion stars have civilization then we could be talking about 150 to 300 civilizations just in our galaxy...  

[beecee]

1 minute ago, Moontanman said:

We are still talking thousands if my math is correct, Isn't 0.001% 1 in 10,000? 

 I bow to your mathematical prowess.  Noting that the numbers involved are astronomical and that the stuff of life being everywhere. As I have said previously, time and distance are great barriers to inter-planetary contact and revelation. A nice article anyway imo.

[Bender]

We only have one data point, and not really random. It can suggest a couple of things about the probability:

- abiogenesis occurred very early and almost as soon as the circumstance was right. This would suggest that it is rather likely.

- evolution to multicellular life occurred billions of years later. Either we live on an exceptionally rare planet were this step took much longer than average, or we live in an average planet, which makes it still pretty likely to occur on other planets around stars like our sun (stable for billions of years). The last option is that this step is exceptionally rare and we are lucky. Since billions of years is the same order of magnitude as the life of a planet, and since our data point is biased, we cannot rule out the possibility that it only happened once in the observable universe.

To conclude: I would be very surprised if no signs of simple life will be found inmy lifetime, but I'm less optimistic about complex, multicellular life.

[Moontanman]

17 minutes ago, Bender said:

We only have one data point, and not really random. It can suggest a couple of things about the probability:

- abiogenesis occurred very early and almost as soon as the circumstance was right. This would suggest that it is rather likely.

This would appear to be true but more data points would clinch the issue. 

17 minutes ago, Bender said:

- evolution to multicellular life occurred billions of years later. Either we live on an exceptionally rare planet were this step took much longer than average, or we live in an average planet, which makes it still pretty likely to occur on other planets around stars like our sun (stable for billions of years). The last option is that this step is exceptionally rare and we are lucky. Since billions of years is the same order of magnitude as the life of a planet, and since our data point is biased, we cannot rule out the possibility that it only happened once in the observable universe.

To conclude: I would be very surprised if no signs of simple life will be found inmy lifetime, but I'm less optimistic about complex, multicellular life.

Multicellular life evolved many times independently on Earth, in fact it has been seen in the lab, we need more data but the data so far seems to indicate that once you have life complex life will arise. 

 https://www.eurekalert.org/pub_releases/2014-01/ajob-foc012414.php

Quote

As a student, Niklas started out being interested in mathematics, but then turned to studying plants because of their "mathematical-like structure." "Multicellularity is a fundamental evolutionary achievement that is capable of mathematical description," comments Niklas, "and one that has occurred multiple times in different plant lineages."

Indeed, no matter how it is defined, scientists agree that multicellularity has occurred multiple times across many clades. Defined in the loosest sense, as an aggregation of cells, multicellularity has evolved in at least 25 lineages. However, even when defined more strictly--requiring that cells be connected, communicate, and cooperate in some fashion or another--it has still notably evolved once in animals, three times in fungi, six times in algae, and multiple times in bacteria.

 

[Bender]

28 minutes ago, Moontanman said:

This would appear to be true but more data points would clinch the issue. 

Multicellular life evolved many times independently on Earth, in fact it has been seen in the lab, we need more data but the data so far seems to indicate that once you have life complex life will arise. 

 https://www.eurekalert.org/pub_releases/2014-01/ajob-foc012414.php

 

Then there is perhaps a required step before multicellularity which is hard. There must* be some extremely unlikely step involved, otherwise it would not have taken billions of years.

* for relevant probabilities of "must"

[Moontanman]

2 minutes ago, Bender said:

Then there is perhaps a required step before multicellularity which is hard. There must* be some extremely unlikely step involved, otherwise it would not have taken billions of years.

* for relevant probabilities of "must"

It's quite possible that oxygen is the trigger once the environment has settled down. It took billions of years for the environment to become stable. Between impacts and greenhouse gas fueled temp swings they could have held back multicellular life..   

[Bender]

Fair enough. We will have to wait for more data points.

[studiot]

21 minutes ago, Moontanman said:

It's quite possible that oxygen is the trigger once the environment has settled down. It took billions of years for the environment to become stable. Between impacts and greenhouse gas fueled temp swings they could have held back multicellular life..   

Not really.

Stromatolites have no mobility, but largely gave way to other single celled organisms that did.

 

https://www.whoi.edu/oceanus/feature/what-doomed-the-stromatolites

[Moontanman]

6 minutes ago, studiot said:

Not really.

Stromatolites have no mobility, but largely gave way to other single celled organisms that did.

 

https://www.whoi.edu/oceanus/feature/what-doomed-the-stromatolites

I'm not sure what you are saying, can you elaborate? 

[studiot]

1 hour ago, Moontanman said:

I'm not sure what you are saying, can you elaborate? 

 

Quote from my link

 

Quote

Bernhard and Edgcomb suspected that another organism may have played a decisive role: foraminifera, or “forams” as scientists often call them. Forams are protists, the kingdom that includes amoeba, ciliates, and other single-celled organisms. Forams are abundant in present-day ocean sediments, where they use fingerlike extensions called pseudopods to engulf prey and to explore their surroundings. In the process, their pseudopods churn the sediments on a microscopic scale.

 

[Moontanman]

3 minutes ago, studiot said:

 

Quote from my link

 

 

Forams could not exist until the environment stabilized and oxygen dominated the planet so I still don't see where you are headed with this..