APOD: Biomarker Phosphine Discovered in of... (2020 Sep 15)

[hamilton1]

Life has been created in the lab from scratch.

I thought trolling was not allowed on here...

[BDanielMayfield]

Life has been created in the lab from scratch.

I thought trolling was not allowed on here...

Not sure that anyone is trolling here, but Chris' bold assertion does beg for evidence backing it up.

Bruce

[neufer]

Life has been created in the lab from scratch.

I thought trolling was not allowed on here...

Not sure that anyone is trolling here, but Chris' bold assertion does beg for evidence backing it up.

"From scratch" is ill defined.

[BDanielMayfield]

I thought trolling was not allowed on here...

Not sure that anyone is trolling here, but Chris' bold assertion does beg for evidence backing it up.

"From scratch" is ill defined.

Agreed, but I used it first in this thread, so what I meant by "from scratch" is from non living raw materials. Just from elements and chemicals naturally present but not derived from prior life. From just what true abiogenesis would begin with.

Bruce

[TheOtherBruce]

Even the respected "Sky at Night" prog on BBC TV last night raised no contradictions. Just, "there's no way that phosphine can form without life!"

What they actually said was "There's no way we know of that this amount of phosphine can form without life". The amount detected is thousands of times more than would be expected by purely chemical reactions. A biochemist interviewed said he'd tried reactions with dozens of combinations of compounds known to exist on Venus; as expected, none of them produced more than traces of phosphine.

And it can't build up over time, like atmospheric oxygen did in the Oxygen Catastrophe on Earth, billions of years ago; something else that was mentioned was that the stuff breaks down fairly quickly under normal Venus atmospheric conditions. Any phosphine detected had to have been produced at most a few hours before.

[BDanielMayfield]

Something most should be able to agree on is the need for more data. Things "known to exist"; all the chemicals there, their actual percentages, the true conditions (temperature, pressure, turbulence, lightning, volcanic gases, etc.) and how these cycle over time are just not known in enough detail as yet. We need to sample this zone of the Venusian atmosphere with some kind of flying and/or floating probe that can stay there long enough to yield solid facts about what's really there.

Until we get the actual on site data at Venus itself all we should say is that a possible biomarker has been discovered there, possibly. Are we even 100% sure that phosphine is the molecule responsible for this absorption band? Have all other possibilities been completely ruled out? Of course not, because we do not as yet know enough about Venus to know all the possibilities there.

Bruce

[neufer]

Click to play embedded YouTube video.

Click to play embedded YouTube video.

Something most should be able to agree on is the need for more data. Things "known to exist"; all the chemicals there, their actual percentages, the true conditions (temperature, pressure, turbulence, lightning, volcanic gases, etc.) and how these cycle over time is just not known in enough detail as yet. We need to sample this zone of the Venusian atmosphere with some kind of flying and/or floating probe that can stay there long enough to yield solid facts about what's really there.

Until we get the actual on site data at Venus itself all we should say is that a possible biomarker has been discovered there, possibly. Are we even 100% sure that phosphine is the molecule responsible for this absorption band? Have all other possibilities been completely ruled out? Of course not, because we don't yet know enough about Venus to know all the possibilities there.

[Chris Peterson]

Something most should be able to agree on is the need for more data. Things "known to exist"; all the chemicals there, their actual percentages, the true conditions (temperature, pressure, turbulence, lightning, volcanic gases, etc.) and how these cycle over time is just not known in enough detail as yet. We need to sample this zone of the Venusian atmosphere with some kind of flying and/or floating probe that can stay there long enough to yield solid facts about what's really there.

Until we get the actual on site data at Venus itself all we should say is that a possible biomarker has been discovered there, possibly. Are we even 100% sure that phosphine is the molecule responsible for this absorption band? Have all other possibilities been completely ruled out? Of course not, because we don't yet know enough about Venus to know all the possibilities there.

Bruce

Semantics, maybe, but I wouldn't call phosphine a possible biomarker. It is a biomarker. But like all biomarkers, it may have non-biological production mechanisms.

[BDanielMayfield]

Something most should be able to agree on is the need for more data. Things "known to exist"; all the chemicals there, their actual percentages, the true conditions (temperature, pressure, turbulence, lightning, volcanic gases, etc.) and how these cycle over time is just not known in enough detail as yet. We need to sample this zone of the Venusian atmosphere with some kind of flying and/or floating probe that can stay there long enough to yield solid facts about what's really there.

Until we get the actual on site data at Venus itself all we should say is that a possible biomarker has been discovered there, possibly. Are we even 100% sure that phosphine is the molecule responsible for this absorption band? Have all other possibilities been completely ruled out? Of course not, because we don't yet know enough about Venus to know all the possibilities there.

Bruce

Semantics, maybe, but I wouldn't call phosphine a possible biomarker. It is a biomarker. But like all biomarkers, it may have non-biological production mechanisms.

I see your point. I just exhaled CO₂. Our potted plant gave off O₂. Both myself and the plant are alive, so therefore CO₂ and O₂ are biomarkers. But to the average person on the street, a few of whom were

jumping up and down

over this Venus biomarker news 'biomarker' is taken to mean 'sign of life!', not 'possible sign of life' as it should. A science educational issue then.

[BDanielMayfield]

Click to play embedded YouTube video.

Click to play embedded YouTube video.

Something most should be able to agree on is the need for more data. Things "known to exist"; all the chemicals there, their actual percentages, the true conditions (temperature, pressure, turbulence, lightning, volcanic gases, etc.) and how these cycle over time is just not known in enough detail as yet. We need to sample this zone of the Venusian atmosphere with some kind of flying and/or floating probe that can stay there long enough to yield solid facts about what's really there.

Until we get the actual on site data at Venus itself all we should say is that a possible biomarker has been discovered there, possibly. Are we even 100% sure that phosphine is the molecule responsible for this absorption band? Have all other possibilities been completely ruled out? Of course not, because we don't yet know enough about Venus to know all the possibilities there.

I like the allusions here Art, 'cuz I'm not the guy crying or sweating in this case.

Sometimes absence of evidence is evidence of absence. After all, don't extraordinary claims call for at least some evidence

Bruce

[neufer]

Until we get the actual on site data at Venus itself all we should say is that a possible biomarker has been discovered there, possibly. Are we even 100% sure that phosphine is the molecule responsible for this absorption band? Have all other possibilities been completely ruled out? Of course not, because we don't yet know enough about Venus to know all the possibilities there.

Semantics, maybe, but I wouldn't call phosphine a possible biomarker. It is a biomarker. But like all biomarkers, it may have non-biological production mechanisms.

<<In medicine, a biomarker is a measurable indicator of the severity or presence of some disease state. More generally a biomarker is anything that can be used as an indicator of a particular disease state or some other physiological state of an organism.>>

<<In chemistry and geology, biomarkers are any suite of complex organic compounds composed of carbon, hydrogen and other elements or heteroatoms such as oxygen, nitrogen and sulfur, which are found in crude oils, bitumen, petroleum source rock and eventually show simplification in molecular structure from the parent organic molecules found in all living organisms.>>

<<A biosignature (sometimes called chemical fossil or molecular fossil) is any substance – such as an element, isotope, or molecule – or phenomenon that provides scientific evidence of past or present life. Measurable attributes of life include its complex physical or chemical structures and its use of free energy and the production of biomass and wastes. A biosignature can provide evidence for living organisms outside the Earth and can be directly or indirectly detected by searching for their unique byproducts.

The atmospheric properties of exoplanets are of particular importance, as atmospheres provide the most likely observables for the near future, including habitability indicators and biosignatures. Over billions of years, the processes of life on a planet would result in a mixture of chemicals unlike anything that could form in an ordinary chemical equilibrium. For example, large amounts of oxygen and small amounts of methane are generated by life on Earth.

An exoplanet's color—or reflectance spectrum—can also be used as a biosignature due to the effect of pigments that are uniquely biologic in origin such as the pigments of phototrophic and photosynthetic life forms. Scientists use the Earth as an example of this when looked at from far away (see Pale Blue Dot) as a comparison to worlds observed outside of our solar system. Ultraviolet radiation on life forms could also induce biofluorescence in visible wavelengths that may be detected by the new generation of space observatories under development.

Some scientists have reported methods of detecting hydrogen and methane in extraterrestrial atmospheres. Habitability indicators and biosignatures must be interpreted within a planetary and environmental context. For example, the presence of oxygen and methane together could indicate the kind of extreme thermochemical disequilibrium generated by life. Two of the top 14,000 proposed atmospheric biosignatures are dimethyl sulfide ((CH₃)₂S) and chloromethane (CH₃Cl). An alternative biosignature is the combination of methane and carbon dioxide.>>

Dimethyl sulfide biosignature in terrestrial atmosphere

---

<<Originally designating a single permanent marker, the Sharpie brand has been widely expanded and can now be found on a variety of previously unrelated permanent and non-permanent pens and markers formerly marketed under other brands. United States President Donald Trump has a well-known preference for using Sharpies [for his signature] on official government documents. In September 2019, Trump was involved in a "Sharpie-gate" controversy, in which - as CNN reports: "Trump defended an apparent Sharpie-altered map of Hurricane Dorian's predicted path.">>

[BDanielMayfield]

Apparently the two words are synonymous. When one looks up Wikipedia's disambiguation page for "biomarker" for this discussion's meaning you get

Biomarker (astrobiology), any substance that provides evidence of past or present life

, but then when you click on the link it takes you to the article for "Biosignature".

I found this part of the biosignature article quite germane to this discussion:

Viability

Determining if a potential biosignature is worth being investigated is a fundamentally complicated process. Scientists must consider any and every possible alternate explanation before concluding that something is a true biosignature. This includes investigating the minute details that make other planets unique and being able to understand when there is a deviation from the expected non-biological processes present on a planet. In the case of a planet with life, it is possible that these differences can be extremely small or not present at all, adding to the difficulties of discovering a biosignature. Years of scientific studies have culminated in three criteria that a potential biosignature must meet in order to be considered viable for further research: Reliability, survivability, and detectability.[5][6][7][8]

Reliability

A biosignature must be able to dominate over all other processes that may produce similar physical, spectral, and chemical features. When investigating a potential biosignature, scientists must be careful to consider all other possible origins of the biosignature in question. There are many forms of life which are known to mimic geochemical reactions. In fact, one of the theories on the origin of life involves molecules figuring out how to catalyze geochemical reactions to exploit the energy being released by them. These are some of the earliest known metabolisms (see methanogenesis).[9][10] In a case such as this, scientists might search for a disequilibrium in the geochemical cycle, which would point to a reaction happening more or less often than it should. A disequilibrium such as this could be interpreted as an indication of life.[10]

Survivability

A biosignature must be able to last for long enough so that a probe, telescope, or human can be able to detect it. A consequence of a biological organism's use of metabolic reactions for energy is the production of metabolic waste. In addition, the structure of an organism can be preserved as a fossil and we know that some fossils on Earth are as old as 3.5 billion years.[11][12] These byproducts can make excellent biosignatures since they provide direct evidence for life. However, in order to be a viable biosignature, a byproduct must subsequently remain intact so that scientists may discover it.

Detectability

For a biosignature to be relevant in the context of scientific investigation, it must be detectable with the technology currently available. This seems to be an obvious statement, however there are many scenarios in which life may be present on a planet, yet remain undetectable because of human-caused limitations.

False positives

Every possible biosignature is associated with its own set of unique false positive mechanisms, or non-biological processes that can mimic the detectable feature of a biosignature. An important example of this is using oxygen as a biosignature. On Earth, the majority of life is centered around oxygen. It is a byproduct of photosynthesis and it is subsequently used by other forms of life to breathe. Oxygen is also readily detectable in spectra, with multiple bands across a relatively wide wavelength range, therefore it makes a very good biosignature. However, finding oxygen alone in a planet's atmosphere is not enough to confirm a biosignature because of the false positive mechanisms associated with it. One possibility is that oxygen can build up abiotically via photolysis if there is a low inventory of non-condensible gasses or if it loses a lot of water.[13][14] Finding and distinguishing a biosignature from its potential false positive mechanisms is one of the most complicated parts of testing for viability because it relies on human ingenuity to break an abiotic-biological degeneracy, if nature allows.

False negatives

Opposite to false positives, false negative biosignatures arise in a scenario where life may be present on another planet, but there are some processes on that planet that make potential biosignatures undetectable.[15] This is an ongoing problem and area of research in the preparation for future telescopes that will be capable of observing exoplanetary atmospheres.

Human limitations

There are many ways in which humans may limit the viability of a potential biosignature. The resolution of a telescope becomes important when vetting certain false positive mechanisms, and many current telescopes do not have the capabilities to observe at the resolution needed to investigate some of these. In addition, probes and telescopes are worked on by huge collaborations of scientists with varying interests. As a result, new probes and telescopes carry a variety of instruments that are compromises to everyone's unique inputs. In order for a different type of scientist to be able to detect something not related to biosignatures, a sacrifice may have to be made in the capability of an instrument to search for biosignatures.[16]

Therefore, a potential biomarker or biosignature can be either true or false. Like Schrödinger's cat, this 'biomarker' in the Venus atmosphere is merely a potential one until we open the box to see if the cause is biological or not.

[JohnD]

Ah! Clear sceptical thinking, no doubt backed up by good science journalism, from New Scientist (3/9/2020, pp 5 and 12)

The Editorial, no less, starts by reminding us that "a whiff of the extraterrestrial ... isn't aliens. It is never aliens."

And on p.12, "Can we verify life on Venus?" (https://www.newscientist.com/issue/3302/) we learn that, yes, an absorbtion line that would be produced by phosphine was detected. One line, that is the "best match" for phosphine, but only one of thousands of absorbtion lines that the compound could produce. No doubt astronomers are seeking others as we speak.
Worse for the alienists, the next argument was that 'there is no abiotic mechanism to produce that much phosphine'. Well, now there is. Truong and Lenine (https://arxiv.org/abs/2009.11904) propose a mechanism by which Venusian volcanoes eject phosphorus compounds that atmospheric conditions could react with to make phosphine, and in sufficient quantities. Their argument depends on there being enough vulcanism on Venus, which we do not know about, but which planned missions to Venus will be investigating.

So, science is on the case, and it's far from proven. Where do you put your money? I'm with the Editor - it's never aliens!

[Chris Peterson]

Ah! Clear sceptical thinking, no doubt backed up by good science journalism, from New Scientist (3/9/2020, pp 5 and 12)

The Editorial, no less, starts by reminding us that "a whiff of the extraterrestrial ... isn't aliens. It is never aliens."

And on p.12, "Can we verify life on Venus?" (https://www.newscientist.com/issue/3302/) we learn that, yes, an absorbtion line that would be produced by phosphine was detected. One line, that is the "best match" for phosphine, but only one of thousands of absorbtion lines that the compound could produce. No doubt astronomers are seeking others as we speak.
Worse for the alienists, the next argument was that 'there is no abiotic mechanism to produce that much phosphine'. Well, now there is. Truong and Lenine (https://arxiv.org/abs/2009.11904) propose a mechanism by which Venusian volcanoes eject phosphorus compounds that atmospheric conditions could react with to make phosphine, and in sufficient quantities. Their argument depends on there being enough vulcanism on Venus, which we do not know about, but which planned missions to Venus will be investigating.

So, science is on the case, and it's far from proven. Where do you put your money? I'm with the Editor - it's never aliens!

Never aliens is likely to prove the case. But I doubt it will be long before we have very solid evidence of life on other planets.

[Ann]

Ah! Clear sceptical thinking, no doubt backed up by good science journalism, from New Scientist (3/9/2020, pp 5 and 12)

The Editorial, no less, starts by reminding us that "a whiff of the extraterrestrial ... isn't aliens. It is never aliens."

And on p.12, "Can we verify life on Venus?" (https://www.newscientist.com/issue/3302/) we learn that, yes, an absorbtion line that would be produced by phosphine was detected. One line, that is the "best match" for phosphine, but only one of thousands of absorbtion lines that the compound could produce. No doubt astronomers are seeking others as we speak.
Worse for the alienists, the next argument was that 'there is no abiotic mechanism to produce that much phosphine'. Well, now there is. Truong and Lenine (https://arxiv.org/abs/2009.11904) propose a mechanism by which Venusian volcanoes eject phosphorus compounds that atmospheric conditions could react with to make phosphine, and in sufficient quantities. Their argument depends on there being enough vulcanism on Venus, which we do not know about, but which planned missions to Venus will be investigating.

So, science is on the case, and it's far from proven. Where do you put your money? I'm with the Editor - it's never aliens!

I'd be very surprised if there is life on Venus (or rather, in the Venusian atmosphere). Then again, I have a lot of confidence in the Universe's ability to surprise us.

I prefer not to guess, however. I vividly remember a "poll" in a Swedish tabloid a few years ago, when the paper asked its readers if there is life on Mars, and the answer was a resounding "Yes!". As I said, I prefer not to guess and not to cast my vote on the matter of life on Venus, but I do think that Venus is very under-explored. We really should try to find out a lot more about it.

Ann

[JohnD]

Never aliens is likely to prove the case. But I doubt it will be long before we have very solid evidence of life on other planets.

The very same issue of NS, not surprizingly, has Dan Falk asking the Q, "Is anybody out there?" He points out that the Drake Equation has such wide error margins that the result can span everything from there being people next door, to us being the only kids on the block. The number of potentially Earthlike planets is clearly so large that life is almost certainly out there. But intelligent life may not be a usual consquence of evolution and the number of such outcomes will be much smaller. Westby and Conselice, from Nottingham U, estimated this June that there could be between 4 and 211 civilisations in the Milky Way, with a best guess of 36. Including us! See: https://iopscience.iop.org/article/10.3 ... 357/ab8225

That puts our neighbours about 17,000 light years away, so until we leap the current bounds of time and space, they might as well not be there.

John

[Chris Peterson]

Never aliens is likely to prove the case. But I doubt it will be long before we have very solid evidence of life on other planets.

The very same issue of NS, not surprizingly, has Dan Falk asking the Q, "Is anybody out there?" He points out that the Drake Equation has such wide error margins that the result can span everything from there being people next door, to us being the only kids on the block. The number of potentially Earthlike planets is clearly so large that life is almost certainly out there. But intelligent life may not be a usual consquence of evolution and the number of such outcomes will be much smaller. Westby and Conselice, from Nottingham U, estimated this June that there could be between 4 and 211 civilisations in the Milky Way, with a best guess of 36. Including us! See: https://iopscience.iop.org/article/10.3 ... 357/ab8225

That puts our neighbours about 17,000 light years away, so until we leap the current bounds of time and space, they might as well not be there.

While I don't think technological life is common, I think it may well evolve often enough for there to be many thousands or millions of examples. But I doubt such species last more than a few centuries once they become technological, so in fact there may be very, very few in a galaxy at any particular time.