Revisiting the Drake Equation

[barbos]

So are you talking about impact to one of these:

n_e = number of planets in a planetary system suitable for life
f_l = fraction of habitable planets where life emerges

Are you saying f_l ought to be 100%?

Yes.

 

[skepticalbip]

So are you talking about impact to one of these:

n_e = number of planets in a planetary system suitable for life
f_l = fraction of habitable planets where life emerges

Are you saying f_l ought to be 100%?

Yes.

Seems reasonable. Assuming that life is just chemistry, life would seem inevitable if given the proper conditions, elements, and sufficient time.

 

[James Brown]

Wouldn't that mean that f₁ should be eliminated entirely from the equation?

 

[bilby]

Wouldn't that mean that f₁ should be eliminated entirely from the equation?

If you like. Setting any of the probabilities to 1 is the same as taking that probability out of the equation.

It's probably better to leave it in there, just so people don't think you forgot to take it into consideration. But if its value is 1, it doesn't affect the final result.

 

[lpetrich]

Titled link: Odds alien life exists boosted by oldest fossils on Earth - CNET

The surface of planet Earth 3.5 billion years ago was probably quite unpleasant, to put it mildly. There were frequent volcanic eruptions, almost no oxygen and higher chances than today of getting bombarded by large asteroids. Yet somehow a diverse group of life forms was already alive and kicking here, despite such seemingly inhospitable conditions, leading some scientists to presume that the same thing almost surely has happened on other planets as well.

SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions
Of the five species that the authors studied, two were primitive photosynthesizers, one was a methanogen, and two were methane consumers.

So the Eubacteria - Archaea split had happened before 3.5 billion years ago. Chlorophyll photosynthesizers are all in Eubacteria, and methanogens all in Archaea.

Those "inhospitable conditions" are similar to some Earth environments that are known to be inhabited by populations of organisms. Like anaerobic ones, ones without O2. So that's a bit of careless and overdramatic journalism.

 

[fromderinside]

This ^^^^^ is why I enjoy these threads.

Scientists actually visit here occasionally.

 

[Don2 (Don1 Revised)]

Titled link: Odds alien life exists boosted by oldest fossils on Earth - CNET

The surface of planet Earth 3.5 billion years ago was probably quite unpleasant, to put it mildly. There were frequent volcanic eruptions, almost no oxygen and higher chances than today of getting bombarded by large asteroids. Yet somehow a diverse group of life forms was already alive and kicking here, despite such seemingly inhospitable conditions, leading some scientists to presume that the same thing almost surely has happened on other planets as well.

SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions
Of the five species that the authors studied, two were primitive photosynthesizers, one was a methanogen, and two were methane consumers.

So the Eubacteria - Archaea split had happened before 3.5 billion years ago. Chlorophyll photosynthesizers are all in Eubacteria, and methanogens all in Archaea.

Those "inhospitable conditions" are similar to some Earth environments that are known to be inhabited by populations of organisms. Like anaerobic ones, ones without O2. So that's a bit of careless and overdramatic journalism.

So in answer to these questions:

Does this finding impact any estimates of variables? Not at all? Are things still just as unclear?

What would you say?

 

[lpetrich]

So in answer to these questions:

Does this finding impact any estimates of variables? Not at all? Are things still just as unclear?

What would you say?

It may push f_l up a bit, by showing that early organisms had already diversified a bit about 3.5 billion years ago. But it may push down f_i a bit, because there are 3.5 billion years between the Apex Chert organisms and us. Why so long? Especially as some prokaryotes can multiply *very* fast and have *very* large populations. Well-fed Escherichia coli bacteria can reproduce themselves once ever 10 minutes, though if their diet is not as good, they may take something like an hour to do so.

So f_l and f_i are still very unclear.

 

[Don2 (Don1 Revised)]

Biological methane production under putative Enceladus-like conditions

Abstract

The detection of silica-rich dust particles, as an indication for ongoing hydrothermal activity, and the presence of water and organic molecules in the plume of Enceladus, have made Saturn’s icy moon a hot spot in the search for potential extraterrestrial life. Methanogenic archaea are among the organisms that could potentially thrive under the predicted conditions on Enceladus, considering that both molecular hydrogen (H2) and methane (CH4) have been detected in the plume. Here we show that a methanogenic archaeon, Methanothermococcus okinawensis, can produce CH4 under physicochemical conditions extrapolated for Enceladus. Up to 72% carbon dioxide to CH4 conversion is reached at 50 bar in the presence of potential inhibitors. Furthermore, kinetic and thermodynamic computations of low-temperature serpentinization indicate that there may be sufficient H2 gas production to serve as a substrate for CH4 production on Enceladus. We conclude that some of the CH4 detected in the plume of Enceladus might, in principle, be produced by methanogens.

https://www.nature.com/articles/s41467-018-02876-y

 

[DBT]

Possibly life on Venus.

Quote;
''A report by Keith Cooper in Astrobiology Magazine says that US and Russian scientists may search for life on Venus by sending a balloon or glider into its atmosphere in 2025.

The mission is called Venera-D, which has been on-and-off-again for quite a while. But back in 2015, after a hiatus in its development, the US and Russia began discussing the project again. And the mission could be used to study dark streaks in the Venusian atmosphere, which may have a biological origin.

Between 50 and 60 kilometers (31 and 37 miles) above its surface, though, there exists a band in the atmosphere with a temperature and pressure similar to Earth, boasting some of the most Earth-like conditions of any planet.

And in this band, scientists have found dark streaks – regions absorbing more ultraviolet light than others – that have an unknown origin. One proposed theory is particulate matter mixed into the clouds. A more exciting theory, though, is that the streaks are the result of biological activity from microbial life lofted high into the atmosphere.''

 

[Kharakov]

Wouldn't that mean that f₁ should be eliminated entirely from the equation?

If you like. Setting any of the probabilities to 1 is the same as taking that probability out of the equation.

It's probably better to leave it in there, just so people don't think you forgot to take it into consideration. But if its value is 1, it doesn't affect the final result.

Of course, in a universe designed to keep life in check so you can guide its evolution... you'd expect f_1 to equal precisely 1/number of inhabitable planets in the universe.

Considering the overwhelming evidence of massive scale projects by intelligent life in the universe.... I'd look for signs of hidden mathematical messages in the constants that govern life.

Show

You know, like... if ... 37 turned up in some constant. Other than the FSC, which is calibrated to 1/(100+37)... or is that why human BBT is 37, and Cscale is 0,100 for something important to life?

Meaningless quackery. Definitely. It's just a coincidence. Nothing to see here. Carry on.

 

[bilby]

https://www.smbc-comics.com/comic/monkey

 

[Don2 (Don1 Revised)]

n_e = number of planets in a planetary system suitable for life
f_l = fraction of habitable planets where life emerges

I saw an article today that had some relevance to these two items.

http://www.techtimes.com/articles/2...niverse-makes-finding-alien-life-unlikely.htm

Substantial Lack Of Phosphorus In The Universe Makes Finding Alien Life Unlikely

Amid efforts to find alien life, scientists have not yet confirmed the existence of an extraterrestrial civilization. Findings of a new study suggest this has something do with the element phosphorus lacking in the cosmos.

Life-Giving Phosphorus

Phosphorus is the 11th most common element on Earth, and it is fundamental to all living things. Phosphorus is one of only six chemical elements on our planet that organisms depend on.

"[Phosphorus] helps form the backbone of the long chains of nucleotides that create RNA and DNA; it is part of the phospholipids in cell membranes; and is a building block of the coenzyme used as an energy carrier in cells, adenosine triphosphate (ATP)," NASA said.

Astronomers have been hunting for phosphorus in the universe because of the role it plays in life on Earth. If the element is lacking in other parts of the cosmos, it could be difficult for alien life to exist.

A new study presented at the European Week of Astronomy and Space Science meeting now suggests that life as we know it is more unusual than previously thought because the universe substantially lacks phosphorus.
_______

I get skeptical when I read things like this because they are so dependent on observations about life on our planet.

Should an estimate of one of the Drake equation variables be based on (in part) supermassive supernovae explosions in regions of habitable planets so that such planets would contain phosphorous?

After googling a little bit, I see that there have been some hypotheses that arsenic could be used in place of phosphorous. I think that even that speculation still accepts basic premises about DNA structure that could be wrong like, for example, does life even need DNA at all--maybe it could use something else entirely.

What are your thoughts on this?

 

[lpetrich]

Phosphorus is important for Earth biochemistry, since it is part of the nucleic-acid "backbone". That structure is - (P) - Rib - (P) - Rib - (P) - Rib - where (P) is a phosphate ion and Rib either ribose or deoxyribose. I think that the main thing that phosphate ions do is have three bonds. With two of them to neighboring (deoxy)riboses, one is left free, and it makes the backbone negatively charged. This may make it interact more easily with molecules that work on it. But it does not seem to me that triply-charged ions are necessary, let alone phosphate ones. Sulfate might also work, though it would have to be a side chain.

 Abundances of the elements (data page) has them for several places and from several sources. I'll use the first column for simplicity, and I'll do phosphorus atoms per magnesium atom.

Crust: 0.035
Seawater: 0.000036
Solar system: 0.0091

I tried again with sulfur, and I found:
Crust: 0.011
Seawater: 0.55
Solar system: 0.47

So for some reason, phosphorus does not dissolve very well, and that is what skews its abundance figures.

 

[Jimmy Higgins]

A new study presented at the European Week of Astronomy and Space Science meeting now suggests that life as we know it is more unusual than previously thought because the universe substantially lacks phosphorus.

Umm... haven't we only come to the conclusion recently, that with there being so many planets, that life has to be likely, not too long ago, as in years? Also, that sentence doesn't really coincide with their article, which talks about a study, of just two supernovas. That is hardly conclusive science. I'm willing to bet the paper the article speaks of, makes no grand conclusions at all.

But this does fit my spoof article from a while ago about a Blog post overextending the conclusions of an article which itself had overextended and simplified the conclusions of a paper that was published.

 

[Jimmy Higgins]

Those "inhospitable conditions" are similar to some Earth environments that are known to be inhabited by populations of organisms. Like anaerobic ones, ones without O2. So that's a bit of careless and overdramatic journalism.

Does it matter if it is the origin though? Is it one thing for life to exist and then adapt in inhospitable conditions verses being able to just spring into existence in the beginning in inhospitable conditions?

 

[skepticalbip]

Those "inhospitable conditions" are similar to some Earth environments that are known to be inhabited by populations of organisms. Like anaerobic ones, ones without O2. So that's a bit of careless and overdramatic journalism.

Does it matter if it is the origin though? Is it one thing for life to exist and then adapt in inhospitable conditions verses being able to just spring into existence in the beginning in inhospitable conditions?

The first life on Earth sprung into existence in what we today consider extremely inhospitable conditions. Someone and their little puppy would die within a couple minutes if they suddenly found themselves anywhere on the planet at the time the first life originated.

 

[Don2 (Don1 Revised)]

I don't know...I think maybe once life is established it spreads to other kinds of extreme environments...like hot versus cold. Then when intelligent life is established (or maybe before) we could be looking at interstellar migration. So initial conditions could be rarer than conditions for continuation. Maybe.

 

[steve_bank]

The equation is what I am used to callingb a 'what if function'.

In the absnse of probabilities and hard data it allows you to acess a result given assumptions.

Givem the lack of a large data set, the probabilities are a SWAG, a scintific wild ass guess. As opposed to a WAG, a plain old wild ass guess.The probabilities may not be Gaussian. The thing to do is assign types of probability distributions and parameters to the variablitues and run Monte Carlo simulations. Easy to do in Matlab, Mathmatica, and Scilab.

If my eyesight was betterI'd set it up.

 

[Swammerdami]

Meiosis is mentioned only once in the thread, but I think it was key — a low-probability event that may not have happened on most planets with life. Meiosis is a complex process that evolved only once on Earth and was essential before evolution could proceed at adequate speed.

~ ~ ~ ~ ~ ~
There is one aspect of quantum physics which confuses me. I'd almost like to start a new thread for my question, but would doubtless be branded a big fool. I'll ask it here, hoping to just be branded a little fool.

Consider photosynthesis, where the initial exciton bounces around haphazardly, "hoping" to make it to the reaction center. The exciton motion is a superposition of various motions, but when the "wave function collapses", the exciton is usually found at the reaction center. Why? It seems like teleology: the reaction center somehow serves as an attractor. Is this correct? If not, why is it that the exciton usually does make it to the reaction center?

Once you adopt such a "teleological" viewpoint and admit wave functions which take a longer while to collapse, some unlikely coincidences can be explained away. (Where's the emoticon for "donning asbestos suit"?)