Scientists Sharpen Skills As They Prepare to Search For and Detect Life *NOT* As We Know It!

IMAGE: A simulation of how an exoplanet imaged by a future successor to Hubble might look with a sunflower shaped starshade occulting, or blocking out the light of the star it orbits, without which the planet would be lost in the glare of the star. Such a mission called Exo-S is being evaluated right now by NASA (below image). The reflected light from such a planet would be examined for signs of life.



I had not seen this article mentioned but I felt it addresses something which often comes up when talking about the scientific search for life beyond Earth on ATS so I felt I should post it along with my comments to place the article in context with all the other research going on this field. I hope you find it useful.

One oft repeated criticism of efforts to look for life on exoplanets with future ground and space telescopes is that by looking for "biomarkers" like free molecular Oxygen (O2) and water vapor (H2O) together with Methane (CH4) or looking for various color signatures (spectra) of photosynthetic life (plants) in the reflected starlight from an an exoplanet, that those of us in the field of astrobiology might miss some other form of life a lot different from that which we know here on Earth.

This criticism while totally valid sometimes misses the fact that we have to start first with what we know since we know it's characteristics the best and so also know how best to look for it. But that by no means is where such a search for life would end.

Such people also might be unaware that as we tune up our techniques and tools to look for life as we know it, there are others who are researching ways to use those same tools and techniques to look for life NOT as we know.

In other words, to look for life with no Earthly analog.

Such is true at my university where back in 2007 researchers at the Virtual Planet Laboratory first began to study how plants on a habitable world around stars different from our sun (redder or bluer) would absorb these stars "sunlight" and by doing that they could determine what color to expect from such vegetation on these distant worlds because depending on the star and the colors of light it predominantly puts out the colors of "leaves" of plants on distant worlds would not necessarily be green. Some would be red. Others, orange, still others, black:



That was then....

Today researchers at the same lab are using computer models to come up with the colors (spectra) of non-photosynthetic life which might cover an entire planet.

Life which would be completely incomparable to any Earthly forrest, grassland, swamp or fungi.

Life. But not as we know it!

From the Financial Express. My comments on the article are in bold type.

new research has suggested that nonphotosynthetic pigments can be biosignatures of life on other worlds.

Using computer simulations, University of Washington researchers found that if organisms with nonphotosynthetic pigments, those that process light for tasks other than energy production, cover enough of a distant planet’s surface, their spectral signal could be strong enough to be detected by powerful future telescopes now being designed. The knowledge could add a new perspective to the hunt for life beyond Earth.
Lead author Edward Schwieterman said that such organisms will produce reflectance, or brightness, signatures different than those of land vegetation like trees, adding that this could push researchers to broaden their conception of what surface biosignatures might look like on an exoplanet or world beyond our solar system.

One of the greatest tools in the search for life elsewhere will be a database of different spectra so that we can recognize it in the plant's shine when we see it. So much research at the Virtual Planet Laboratory at UW and the newly christened Carl Sagan Institute at Cornell is devoted to building up such a database both by studying the colors of various earth life, from bacteria and fungi up to macro flora (forests, etc) as well as research into other possibilities unlike this Earth life but just as possible, viable and alive through use of advanced computer modelling.

Continuing...

Exoplanets are much too far away to observe in any detail; even near-future telescopes will deliver light from such distant targets condensed to a single pixel. So even a strong signal of nonphotosynthetic pigments would be seen at best only in the “disk average” or average planetary brightness in the electromagnetic spectrum, Schwieterman said.

This is going to become more and more important as over the next 10-15 years telescopes which have begun construction on Earth in Chile and Hawaii as well as the design for a large optical replacement for Hubble are completed.

And so....

This broader perspective might allow them to pick up on something they might have missed or offer an additional piece of evidence, in conjunction with a gaseous biosignature like oxygen, for example, that a planet is inhabited, Schwieterman said.
The study is published in May in the journal Astrobiology.

AWESOME!!!

a reply to: JadeStar

This isn't completely NEW news, but thanks for Bringing up this Topic. Especially now. Really Helps take the mind off the Negatives.

Great Excavation!

Star!

originally posted by: SirKonstantin
a reply to: JadeStar

This isn't completely NEW news, but thanks for Bringing up this Topic. Especially now. Really Helps take the mind off the Negatives.

Great Excavation!

Star!

It's not completely new no, but this study and work modelling the spectra of completely alien life with no Earthly analog is fairly new and I thought people might be interested in it since it answers a common criticism on ATS of astrobiology in general.

I don't think many people are aware of such efforts because reading the comments sections of every story on the search for life around other stars inevitably has someone say "But what about life not as we know, you know completely alien, why don't they look for that??!"

Well they will and this is the prerequisite research to allow for that hunt.

I'm going to have to do a bit more reading, but this sounds fantastic!
S&F

a reply to: JadeStar

I think this may coincide with the Pope and Scientist claiming that Extraterrestrial life Will be found in....i think they said something easy along the lines of 20yrs from now....like DUH!lol

a reply to: JadeStar

A+ thread JS! I've held the contention that its the same with folks waiting for and expecting the "aliens" drop in or be disclosed contacts been made.

As in your op here, I believe we won't know it if we saw it...we just don't know what (yet) to even look for....either "out there" or standing right in front of us.

Thanks again JadeS....MS

This points to an old metaphor, "what constitutes life". Just as many great author and artist have expressed, if a machine was given consciousness, and can self replicate, is it alive? If so, chasing carbon seems eliptical. Is silicon based life such a stretch? As we know, various minerals can facilitate a charge, precursor to conscious. This warrants revision.

originally posted by: admirethedistance
I'm going to have to do a bit more reading, but this sounds fantastic!
S&F

What i like most about this pigment based search for life research ist that it is very easy to explain to the average person. Far easier than than talking about the spectroscopic detection of different gasses in an exoplanet atmosphere during a transit.

We can just say, "we're going to build huge telescopes to collect a lot of light from distant planets similar to Earth around other stars and see if they're covered with anything living."

Most people can understand that because at it's most basic level it's just looking for different combinations of color.

By comparison I find it challenging to explain things like transit spectroscopy as a way to analyze a distant planet's atmosphere to the same average person who might not know that all light has fingerprints of not only the source that emitted it but also of what it not only passes through but bounces off of before it reaches our telescopes.

It's not enough to say, "we know this" without explaining also how we know what we know.

originally posted by: SirKonstantin
a reply to: JadeStar

I think this may coincide with the Pope and Scientist claiming that Extraterrestrial life Will be found in....i think they said something easy along the lines of 20yrs from now....like DUH!lol

Yeah, that's the prevailing view in general. And that was reiterated here in this recent interview with Sara Seager after a talk she gave at the Perimeter Institute in Canada.

The Pope should know this as well because the Vatican Observatory is heavily involved in exoplanet research and they co-ordinate a yearly conference on exoplanets and research related to looking for life on them (the hunt for biosignatures):

originally posted by: trifecta
This points to an old metaphor, "what constitutes life". Just as many great author and artist have expressed, if a machine was given consciousness, and can self replicate, is it alive?

I'd answer, "maybe".

If the machine simply made 100% identical copies of itself I'd say no because that's how crystals grow and they're not alive. However if such a computer through some sort of "breeding" algorithm could take in other information to make different, perhaps even better copies of itself which were able to do the same for generations then it would be very hard to argue that machine was not alive.

I mean, it would pass the Turing test, be self aware and concerned with it's offspring to the point where it try to produce a better version of itself, on it's own.

If you talk to the SETI crowd most of them feel that our first detection of intelligent life is more likely to be with just such machines or some combination of that machine with advanced biology, rather than fully biological, none augmented beings like us.

If so, chasing carbon seems eliptical. Is silicon based life such a stretch? As we know, various minerals can facilitate a charge, precursor to conscious. This warrants revision.

It's two different questions really.

Could silicon based life form under the right conditions? Answer: maybe. complex silicate based chemistry is possible but it is unknown whether it could ever become alive.

the next question is, if such silicon based life existed would it be the most common life out there? To that i'd probably lean towards a 'no' simply based on the differences between organic chemistry and silicate based molecules.

The reason being that while both carbon and silicon are common elements in the universe, complex chemical bonds which lead to things like RNA and DNA form rather easy compared to anything which might produce a silicon based "biochemistry".

So since nature favors what is easy, available and plentiful I'd tend to think that nature probably favors carbon based life. It would take silicon based life longer to form since carbon atoms like to "hook up" and are rather promiscuous compared to silicon atoms.

So carbon based life would get a head start on silicon based life if the latter is even possible.

Nice topic, Jade.

As you point out, I understand that the search for ET life seems to be concentrating on "Life as we know it" is because we actually know how to detect "life as we know it", but really don't have definitive ways of testing for "Life as we DON'T know it".

We could possibly be looking directly at microbes that are "life as we DON'T know" and not even be able to recognize them as being life. However, I think astrobiologists are working towards models of alternate types of life -- models by which they may be able to detect the biosignatures of those potential alternate types of life as we don't know it.

We know that by finding excesses of free oxygen in an atmosphere, that would be a major indcation of life as we know it, but scientists are starting to understand how other "imbalances" or "disequilibriums" of atmospheric gases could also indicate the presence of life that is not like Earth life.

Here is an example of research being done by NASA astrobiologist Chris McCay trying to determine if certain chemical disequilibrium on Saturn's moon Titan indicates the possibility of methane-based life there:

What is Consuming Hydrogen and Acetylene on Titan?

Excerpt:

Two new papers based on data from NASA's Cassini spacecraft scrutinize the complex chemical activity on the surface of Saturn's moon Titan. While non-biological chemistry offers one possible explanation, some scientists believe these chemical signatures bolster the argument for a primitive, exotic form of life or precursor to life on Titan's surface. According to one theory put forth by astrobiologists, the signatures fulfill two important conditions necessary for a hypothesized "methane-based life."

It should be pointed out that natural (non-life) processes may also be responsible for these disequiliriums on Titan, but the idea of looking for life in this manner is intriguing. Considering the possibilities of what kind of biosignatures non-earth-like life may display will be helpful in the future efforts in knowing how to recognize "life as we DON'T know it" as actually being life when we see it.

originally posted by: mysterioustranger
a reply to: JadeStar

A+ thread JS! I've held the contention that its the same with folks waiting for and expecting the "aliens" drop in or be disclosed contacts been made.

As in your op here, I believe we won't know it if we saw it...we just don't know what (yet) to even look for....either "out there" or standing right in front of us.

Thanks again JadeS....MS

Thanks the kind words.

And yes, it is quite possible we could totally miss it if we don't continue to broaden our search as we learn more about what is possible out there.

I forget who said it but there's a quote which goes something like "If we rule out the impossible what we are left with is the inevitable."

Aliens are not impossible. We know that. The fact that life in general exists tells us that much. No matter how rare life may be. in a galaxy of 200 billion stars and many times as many planets, we're probably not alone in our own galaxy much less the trillions of other places in the observable universe.

That's why the smart money is on us finding life in the next 30 years or so. We know life arose pretty quickly on the Earth not long after it cooled down from formation and there is a planet for just about every star (usually more than one) so while some wait for the aliens to land or there to be some sort of "disclosure" others are developing ways to find them (or their microbial cousins more likely) on distant planets around other stars.

If mother nature is kind, we will have an answer in the not too distant future and it could be from a world not that far from Earth.

a reply to: JadeStar

Agreed. We are on the verge of discovering what's out there....and why we failed to recognize it....while for the most part...we look for arms and legs, ships and orbs, microbes and spores....and all along...we just need to think out of the box....to look for what's in it....

Prepare to be amazed....thanks again.

MS

originally posted by: Soylent Green Is People

Nice topic, Jade.

As you point out, I understand that the search for ET life seems to be concentrating on "Life as we know it" is because we actually know how to detect "life as we know it", but really don't have definitive ways of testing for "Life as we DON'T know it".

Exactly. That's why the modelling work these researchers did is importance. It's teaching us how we might look for life we don't have on Earth but which according to models could also exist.

We could possibly be looking directly at microbes that are "life as we DON'T know" and not even be able to recognize them as being life.

Yes. That's why there are databases being created of the spectra (colors) of bacterial colonies and stuff, so if we could recognize something which might not initially look like a planet with life as actually a planet covered with a completely alien microbial mat.

However, I think astrobiologists are working towards models of alternate types of life -- models by which they may be able to detect the biosignatures of those potential alternate types of life as we don't know it.

Yes they are the research you point out on Titan below is a prime example of that. We know interesting chemistry is taking place on Titan, could something be alive on it? It's a fascinating question and hopefully before we send the next lander (or quite possibly a boat) to Titan we'd want to make sure to design experiments which would not miss some completely alien biochemistry taking place on TItan.

We know that by finding excesses of free oxygen in an atmosphere, that would be a major indcation of life as we know it, but scientists are starting to understand how other "imbalances" or "disequilibriums" of atmospheric gases could also indicate the presence of life that is not like Earth life.

Exactly. We also know, cautiously of geological things which could mimic the presence of life on a world. Not even free oxygen is immune because an exoplanet losing it's ocean could look similar to instruments which are being designed for the next-gen telescopes.

So we have the problem of if everything is life. then nothing is life.

In other words if we don't also develop techniques to identify these false positives at the same rate we are developing the abilities to detect life then we could be faced with a bunch of worlds which look alive but none which is that convincing to say so with certainty.

That's like the "nightmare" scenario of astrobiology which keeps a lot of very smart people up late at nights working on ways to increase our understanding both in the areas of life detection as well as ruling out abiotic false positives which would mimic a real detection.

Here is an example of research being done by NASA astrobiologist Chris McCay trying to determine if certain chemical disequilibrium on Saturn's moon Titan indicates the possibility of methane-based life there. It should be pointed out that natural (non-life) processes may also be responsible for these disequiliriums on Titan, but the idea of looking fo life in this manner is intriguing.

What is Consuming Hydrogen and Acetylene on Titan?

Excerpt:

Two new papers based on data from NASA's Cassini spacecraft scrutinize the complex chemical activity on the surface of Saturn's moon Titan. While non-biological chemistry offers one possible explanation, some scientists believe these chemical signatures bolster the argument for a primitive, exotic form of life or precursor to life on Titan's surface. According to one theory put forth by astrobiologists, the signatures fulfill two important conditions necessary for a hypothesized "methane-based life."

Yes, it's exciting research! Something is creating this disequilibrium and we know from NASA's Cassini and the ESA's Huygens lander that complex chemistry is taking place on Titan.

What else might lurk in it's hydrocarbon lakes?

I'd love it if we could land a robotic boat there in the 2030s. NASA's TiME (Titan Mare Explorer) proposal was intriguing.

originally posted by: JadeStar

originally posted by: trifecta
This points to an old metaphor, "what constitutes life". Just as many great author and artist have expressed, if a machine was given consciousness, and can self replicate, is it alive?

I'd answer, "maybe".

If the machine simply made 100% identical copies of itself I'd say no because that's how crystals grow and they're not alive. However if such a computer through some sort of "breeding" algorithm could take in other information to make different, perhaps even better copies of itself which were able to do the same for generations then it would be very hard to argue that machine was not alive.

I mean, it would pass the Turing test, be self aware and concerned with it's offspring to the point where it try to produce a better version of itself, on it's own.

If you talk to the SETI crowd most of them feel that our first detection of intelligent life is more likely to be with just such machines or some combination of that machine with advanced biology, rather than fully biological, none augmented beings like us.

If so, chasing carbon seems eliptical. Is silicon based life such a stretch? As we know, various minerals can facilitate a charge, precursor to conscious. This warrants revision.

It's two different questions really.

Could silicon based life form under the right conditions? Answer: maybe. complex silicate based chemistry is possible but it is unknown whether it could ever become alive.

the next question is, if such silicon based life existed would it be the most common life out there? To that i'd probably lean towards a 'no' simply based on the differences between organic chemistry and silicate based molecules.

The reason being that while both carbon and silicon are common elements in the universe, complex chemical bonds which lead to things like RNA and DNA form rather easy compared to anything which might produce a silicon based "biochemistry".

So since nature favors what is easy, available and plentiful I'd tend to think that nature probably favors carbon based life. It would take silicon based life longer to form since carbon atoms like to "hook up" and are rather promiscuous compared to silicon atoms.

So carbon based life would get a head start on silicon based life if the latter is even possible.

What sort of atmosphere would silicon based life develop in?

originally posted by: Sunwolf

What sort of atmosphere would silicon based life develop in?

Seeing as how we don't even know such life exists that's tought to say.

So I'll reframe the question and answer it. We might first want to ask what atmospheric characteristics would a planet have to have for complex silicon based chemistry to thrive?

Because before you can have life you have to have it based on some complex molecules.

Silicon forms it's most complex molecules when it is in liquid form because like water, that is it's densest state. The melting point for silicon is 1,414°C and it boils and becomes gaseous at 3,265°C.

So instead of looking for silicon based life by studying planets like our Earth we might want to study absolute hell holes from our perspective.

The seas of such a planet would not be made of water but from liquid iron hotter than inside of a blast furnace. One could imagine Silicon-Aluminium based complex chemistry and an atmosphere of sulfur vapor.

An atmosphere of gaseous sulphur which occassionaly rains liquid iron could be your best place for silicon-based life to evolve.

Kepler even spotted a planet which would come close to that description, enter, Kepler-7b

Unfortunately though, there is a tragic flaw in trying to establish silicon as a suitable biological replacement carbon.

This is because silicon just LOVES hooking up with oxygen. When carbon is oxidized during the respiratory process of a terrestrial organism (see respiration), it becomes the gas carbon dioxide – a waste material that is easy for a creature to remove from its body. The oxidation of silicon, however, yields a solid because, immediately upon formation, silicon dioxide organizes itself into a lattice in which each silicon atom is surrounded by four oxygens. Disposing of such a substance would pose a major respiratory challenge.


Life-forms must also be able to collect, store, and utilize energy from their environment. In carbon-based biota, the basic energy storage compounds are carbohydrates in which the carbon atoms are linked by single bonds into a chain.

A carbohydrate is oxidized to release energy (and the waste products water and carbon dioxide) in a series of controlled steps using enzymes. These enzymes are large, complex molecules (see proteins) which catalyze specific reactions because of their shape and "handedness."

Another feature of carbon chemistry is that many of its compounds can take right and left forms, and it is this handedness, or chirality, that gives enzymes their ability to recognize and regulate a huge variety of processes in the body.

Silicon's failure to give rise to many compounds that display handedness makes it hard to see how it could serve as the basis for the many interconnected chains of reactions needed to support life.

There is also no observational evidence that such silicon-based life is at all easy, in fact it might just be impossible because of the absence of silicon-based biology, or even silicon-based prebiotic chemicals, is also suggested by astronomical evidence.

Wherever astronomers have looked – in meteorites, in comets, in the atmospheres of the giant planets, in the interstellar medium, and in the outer layers of cool stars – they have found molecules of oxidized silicon (silicon dioxide and silicates) but no substances such as silanes or silicones which might be the precursors of a silicon biochemistry.

So, if silicon-based life is even possible then it is likely to be A LOT rarer than carbon-based life because it would requirer conditions which are rarer than on Earth and the precursor "biochemisty" for silicon-based life would seem to be very difficult if not impossible.

Nature typically likes what is easy and available and we know that organic compounds based on carbon are just about every where we look.

Anyone waiting for silicon-based life, might have a long, lonely wait.

On the other hand...www.sciencedaily.com...

originally posted by: stormbringer1701
On the other hand...www.sciencedaily.com...

One thing that article isn't telling me is the metallicity of these 11 billion year old solar systems. So when they say "Earth-like", I wonder what the metallicity is and elemental compositions are similar to Earth.

An 11 billion year old star is most likely to be a population II star, which is metal-poor. Our sun is a population iii star, which are relatively young, and have an abundance of metals and other heavy elements.

originally posted by: Soylent Green Is People

originally posted by: stormbringer1701
On the other hand...www.sciencedaily.com...

One thing that article isn't telling me is the metallicity of these 11 billion year old solar systems. So when they say "Earth-like", I wonder what the metallicity is and elemental compositions are similar to Earth.

An 11 billion year old star is most likely to be a population II star, which is metal-poor. Our sun is a population iii star, which are relatively young, and have an abundance of metals and other heavy elements.

I think I read an article that said metallicity isn't as important as once thought in reference to this sort of thing. I don't remember the details exactly. been too long.