Why THIS Planet Would Have RED Plants

[Music] a couple months ago i released a video about 16 possibly habitable exoplanets and the very first one i talked about was this one right here kepler-1a when it was originally discovered back in 2014 it represented an amazing moment not only in the search for earth-like exoplanets but for astronomy as a whole as this was the very first earth-sized planet found within its star's habitable zone proving not only that earth-sized planets are relatively common but also that we are capable of finding such planets from here on earth since its initial discovery we've continued to learn and deduce new information about this alien world with one of the most notable aspects being the thought that plant life here would take on a reddish color rather than the green we're used to seeing on earth but when i brought this up in the video i got a lot of comments saying that this wasn't actually the case and that i was wrong the only problem is i don't like being called wrong especially when i'm not wrong but okay i'll admit it some of the points you guys brought up in the comments were fair and a few of them well a few of them even made sense i think at the heart of this disagreement is simply the fact that i had 15 other exoplanets to talk about so i just couldn't commit enough time to explaining the logic behind this so instead that's what i dedicated this video to figuring out today we're getting to the bottom of exactly what color plants we'd find on kepler-186f and planets like it the only way to really understand the red plants of kepler-186f is to first take a look at the plants of earth and ask ourselves why these are green while this might seem like a simple and straightforward question well it's not and actually we still don't really know the answer to it i mean okay we know the technical aspects of it all chlorophyll is the green pigment found within structures called chloroplasts inside the leaf that absorbs light kickstarting the process of photosynthesis but why chlorophyll why green that's what's still unclear to figure this out we need to get deeper into the nature of light across the entire range of electromagnetic waves only a very small portion is what we see as light contained within visible light is a spectrum of different wavelengths that appear to us as all the different colors the way we actually see things is by light shining from a source and being partially absorbed and partially reflected which then enters our eyes if an object absorbs all the light coming its way it will appear black because nothing is reaching your eyes if the opposite happens and an object reflects all of the light then it looks white but if all of the colors except red for example are absorbed then red is the only wavelength of light being reflected which is what we end up seeing leading us to perceive that object as red so what this means is that leaves that are green don't absorb the green wavelengths of light but rather reflect them while absorbing the rest of the spectrum but you see this is weird oh man but you see this is weird i mean think about it the whole purpose of a leaf is to obtain energy by absorbing light so you'd think they'd want to maximize their energy intake by absorbing all wavelengths in turn making them black but as we can clearly see they don't and actually not only do leaves have color but most of them are pretty bright too meaning they actually reflect a fair amount of sunlight coming their way so this all begs the question why are plants rejecting some forms of light and again why specifically green light this is what we're still trying to figure out but a paper published in science only last year might have finally cracked the case so let's take a look you know what i really just don't feel like reading plus there's nothing visual to show when just explaining text so how about instead we talked to one of the researchers that actually contributed to this paper and get him to explain so i thought first you could maybe just introduce yourself to you know the people watching at home who you know don't read scientific papers too often sure sure so my name is nathaniel gaber and i am a professor at the university of california in riverside which is in the la metro area i am actually by training a quantum physicist so i study quantum mechanical electronic devices but now i've actually have a vast research program in quantum biology so we're searching for quantum mechanics in biology and that has led to a lot of fundamental questions about uh the rules of life you know what what do we know about life are there systematic rules about it and so that's where my research really lies is how quantum mechanics and life interact and how that's important to bigger problems ah great awesome uh so let's just get right into it before we you know before we get talking about kepler 186 f or planets and stars uh can i just get a quick explanation of the paper that uh brought me to you or simply you know why are plants on earth green yeah this is a question that i i think many many people have asked mostly uh early on it was mostly botanists who were asked this question later on other types of scientists started asking this question and i would say that my work just kind of sits in a in a long tradition of trying to answer this question uh and maybe we we've gotten on to something but there are lots of different aspects to it and the basic observation came from something really simple which is if you think about where a lot of the light comes from the sun where what colors that light is a lot of it sits in kind of the visible portion there's also some infrared so it's this kind of broad spectrum but a lot of it sits right in the visible and it turns out that it's very very bright in the green wavelengths okay and so when i was a graduate student i was kind of supposed to be listening to a conference a seminar and i was daydreaming about this question and it became immediately puzzling to me because if i asked i wanted to build a device you know say a solar cell that chose the right color the perfect color to absorb i would argue that you want to absorb green light because it has a lot of optical power there's lots of green light coming from the sun but then i realized immediately that when we look at plants they're all green and so it's spitting out it's reflecting all of the light that i just assumed would be the perfect light to gather so then it was this long process of trying to understand what is nature actually trying to do and why is it spitting out all of that green light why is it reflecting all of that green light many people have tried to answer the question and i came up with a pretty simple hypothesis which was maybe what plants are doing is not trying to just get the most light possible right they've gotten past that point they've kind of adapted over time that if there's too much light available they don't want to be burned right you don't if you ever leave your plant like i live in the desert basically if we leave plants outside on the porch they don't survive right yeah there's a clear and you know obvious danger of too much light and so our hypothesis was maybe what they're doing is trying to regulate the amount of light that they get in so you can imagine i have this crazy environment right i have day and night and i have clouds and i have other plants swinging their leaves around and i have this really crazy dynamic light environment but what i want as a plant uh is to basically very carefully turn that into sugar right or or fuel or solar fuel right so i have this problem where it's just like i have this incredibly noisy environment that i need to regulate to get a steady flow of energy during the day and it's the same problem humans have right we bring in food and and resources in kind of a random fluctuating way but our body has a lot of regulation mechanisms to deal with that energy so that's where the idea started and we said okay let's just start with that one basic assumption and then start to build mathematical models based on that so you know it's very axiomatic like mathematics where you say that's our only assumption is that plants don't want to maximize they just want to carefully regulate and what we found is if you have two pigments so like in plants we know it's chlorophyll a and chlorophyll b if you have two there's a very special function that the plant can do and that function is to regulate if you only have one so let's say we had plants that were just one pigment you can't do this regulation function but as soon as you have two then you have this opportunity to regulate the amount of energy coming in and so plants are kind of doing that and they have two pigments where they can kind of randomly switch between which one's working and which one's not working and that has an advantage in the sense that i can always generate energy i can always produce energy but i regulate this idea of regulation was demonstrated in nathan's paper by three graphs the first shows a plant's energy output if light is absorbed where it peaks we can see in a natural setting this produces an incredibly noisy field with huge degrees of variance that when all added up produces a very poorly tuned outcome where even though there were incredibly high peaks the overall energy output is inconsistent and as a result experienced lots of time being both overpowered and underpowered without much time spent at the optimal capacity compare this to a set of absorbers that choose to ignore the peak wavelengths of light and rather takes in a narrower range what's produced is a far more stable influx of light ultimately resulting in a balance between being overpowered and underpowered maximizing the time spent at optimal levels proving this to be a very finely tuned strategy of course you can reject too much light as well as was shown by placing absorbers very close together away from the peak which produces minimal degrees of variation but because the intake is so limited it fails to capture light efficiently and as a result produces less energy overall what we can see is that plants actually maximize their energy output by rejecting some of the light coming their way and the easiest way to achieve this is to reflect wavelengths where the sunlight spectrum peaks so finally looking at the sun's actual spectrum we can see that it peaks around 500 to 550 nanometers which is what we see as green meaning it's this wavelength that plants must reject in order to operate at peak efficiency okay so say it with me in order to stabilize their light intake and maximize efficiency plants must block out green light because that's where our sun's spectrum peaks making them yeah green problem solved wait wait wait wait hold on this video was supposed to be about why plants on kepler-186f are red not why plants on earth are green so now that we understand how and why plants color their leaves the way that they do we can now apply this theory to a different planetary system to sum up what we've learned so far the color of a plant is ultimately dependent on the light coming from its host star so before we can even look at kepler-186f we first need to take a look at kepler-186 unlike our sun which is a g-type star whose light ends up in the yellowish to white range kepler-186 is a much smaller and colder m-type star which instead tend to give off an orangish red glow earning these types of stars the nickname red dwarfs this means that instead of emitting light within this range mostly within the visible spectrum stars like kepler-186 emit light closer to this range peaking somewhere far outside the visible spectrum into the infrared wavelengths what little emissions from m-type stars that do come in the form of visible light are shifted severely towards the red you know hence the name red dwarfs and all bathing any planets orbiting such a star in pale red light [Music] now i caught a lot of flack in that last video for saying the light from a red dwarf would be red so let me clarify to our eyes the light would still look white for the same reason that light from our sun looks white as well despite consisting of varying degrees of each wavelength the sheer amount of light coming from stars virtually washes out all other hints of color but here's the thing our eyes weren't meant to look directly at the sun but plant's entire existence literally hinges on their interaction with sunlight meaning they do pick up on these differences or at least they do here on earth and so if we assume plants on kepler-186f are equally sensitive then it would only make sense for them to block out the highest degrees of light they're getting in the red wavelength while absorbing all others giving them yes a reddish color but okay if you don't trust me then let's ask our expert on the subject only looking at what wavelengths of light are reaching the surface of kepler-186f or you know planets like it what color could you expect plants to be in an environment around red dwarfs yeah this is this is one of the questions that our our paper tried to answer even here on earth actually so let me start on the earth piece and then we'll go to what we'll see the extension to the exoplanets so one of the things we did is we said if you had terrestrial surface plants our model of regulation predicts that they would be green okay but we had another case we had several other cases one is a case of photosynthetic bacteria that live in essentially in mud puddles but they're typically under the canopy of trees and so when light shines through that canopy of leaves it shifts towards the infrared a little bit so the spectrum that these bacteria see at the bottom is a bit different than what the leaves are seeing above and so we plugged that spectrum in we said let's assume that they're seeing this little bit more red uh spectrum and you see that it gives the right answer they absorb again with in proportion to what spectrum of light they see and so this is a natural extension once you know what the the peak of the spectrum is so let's say an m-type star it tends to peak more in the infrared so once you know that peak if you plug in our model it suggests that oh to regulate against that you would actually avoid that peak color and so the plants if you were staring at them would look more red so in principle yeah we would expect for planets like uh you know this kepler it it basically would shift further and further red which means those plants would look you could imagine these really eerie looking plants you know looking basically dark red while it might be off-putting at first i've found that the longer i look at images of plants recolored to be red the more comfortable i'd become with it at a certain point you realize that the colors we encounter here on earth are merely the result of our environment and the door is completely open for color palettes radically different from the ones we're familiar with to prevail [Music] do [Music] do now okay at this point this seems like a pretty open and closed case right well okay to the credit of all the people who commented to tell me that i was wrong there actually is a strong case to be made for another color to reign supreme here again everything comes back to the characteristics of the parent star if you'll remember i said m-type stars are far smaller and colder than g-type stars like our own meaning they characteristically give off less light for instance kepler-186 is thought to only provide about five percent of the luminosity that our sun gives off to make up for this kepler-186f must orbit much closer to its star than we do to ours even still kepler 186's inherent dimness means 186 f only receives about 32 percent of the illumination that the earth receives making this planet not only a cold one but also a dim one [Music] on a surface level this would likely mean the extension of massive ice sheets across much of the surface but on a biological level what this means is that the great excess of light that plants on earth experience may not be the case on kepler-186f and instead light may be a rare commodity forcing plants to employ a different strategy to collect as much light as possible adapting to this low light environment rather than reflecting some forms of light in favor of a more stable income plants might instead choose to open the floodgates and absorb any and every wavelength of light they can get their hands on i guess to make up for the lack of light this would make plants here extremely dark even black instead of red so does this mean i was wrong after all well okay so far we've seen two equations plants can use to determine their pigmentation now the argument lies in which pathway the planets of kepler-186f would actually choose to a degree they both make sense i mean red makes more sense if there's excess light and black makes more sense if light is a limiting resource and yeah if that's all there was to it then i might actually agree with you guys and say black is more likely but there's still one thing we need to consider and again it all comes down to orbiting a red dwarf like i said a minute ago in order to receive enough light energy to sustain liquid water and the potential for life kepler-186f must orbit much closer to its star at a distance of only about 0.4 astronomical units which for comparison mercury the closest planet to the sun in our solar system orbits at around 0.39 au while the earth of course sits at precisely 1 au not only does this put kepler-186f very close to its parent star but also close to kepler-186b kepler-186c kepler-186d and kepler-186e so while the sky of kepler-186f may be a dim one at least crammed in close to four sibling planets of similar size it would also be a crowded sky serving as a front row seat to the rest of the kepler-186 system this closeness of orbit also means kepler-186 and planets like it all have a high likelihood of being tidally locked naturally this has a huge impact on the distribution of light and heat across the planet which by extension drastically affects any biology harbored on the surface but exactly how this would affect plant life is well hard to say as there's a lot of things to consider so before i get into it i wanted to ask nathan for his feelings on this so finally the biggest impact in this you know overall is kepler-186f obviously or probably doesn't orbit the same way that the earth does uh so what are your thoughts on how a tidally locked planet would you know affect the coloration of plants yeah this is a really fun question actually so the interesting thing is that if i think of what a tidally locked star is it's just that the face of the star is always getting bombarded uh with that the star's light and so what you can imagine is that on one side of the star it's very very bright all the time right on one side of the planet right yeah right yeah one time one side of the planet it's very bright it's like daylight all the time the other side of the planet is uh you know night time all the time but there's a gradual transition right so there is a ring you could imagine that right at the place where light and dark meet there's this kind of ring of twilight um and one interesting question comes okay well you know what is the difference between the hot side and the cold side um and it turns out from many many estimates from from the astronomy community is that it's not so much different from the temperature of our poles so like the north pole to the equator for similar reasons right we're always ro our planet is always rotating but really at the poles they get pretty consistent light conditions and so that seems amicable to life right it's not such an extreme temperature gradient that you would expect things not to live and so if you have this planet that you're always staring at the sun probably life is is going to have a hard time right on the surface right right of the surface but as you go back and get a little bit darker and darker you'll start to see conditions where if you were looking face on this planet it would be pretty awesome there's this line of of kind of perfect conditions and this line has a name they call this the terminator line it's basically where the brightness meets the the darkness of this tidally locked planet and that's where i would expect and i think many others would expect that you could get just the right combination of light conditions to uh to to start to see photosynthetic life okay so taking nathan's words into account it's likely that life would only inhabit a narrow range on the planet where light conditions aren't too strong and aren't too weak but this creates essentially two different light conditions or really two different environments on one side of this twilight region although kepler-186f only receives what 32 percent of the light that the earth receives because there's no day night cycle here instead of roughly 12 hours of light in 12 hours of dark plants would be in constant light without any respite from the sun plants here would likely encounter excess amounts of light even more so than here on earth this leads me to believe plants towards the front of the terminator zone would have the luxury of being very selective in the light they receive in turn evolving to reject the strongest wavelengths of light making plants here not only red but potentially bright red [Music] [Music] do [Music] but as you move away from the sunny side gradually the intensity of light would diminish until it's only ambient light coming from just below the horizon here we'd find a light deprived environment where plants may in fact adopt a more conservative approach to collecting light consequently darkening their bodies and leaves altogether this would result in a transition from extremely bright red plants near the focus to near black plants clinging to the planet's underside with all sorts of variation between the two it would be somewhere between these two extremes that life would reach its climax where it's not too hot not too cold not too bright and not too dark that plant life would likely settle into a comfortable middle ground where they're not bright red but also not black settling probably around some sort of dark red just like how plants on earth aren't always the exact same color plant life here would exist across a range and it'd be up to the local conditions to select which pigments could survive where and you know if you talk to for instance uh you know botanists or people who study photosynthesis or biologists in general they'll tell you that biology and life has a tendency to adapt and an incredible ability to adapt so like you said you would see this kind of spectrum of essentially adaptations to the light conditions and i would expect that it would be very diverse right you wouldn't just expect to see this perfect ring around the circle you would actually see this kind of diversity of behavior so you have this really interesting uh playground to think about how an ecosystem with you know diversity would evolve on this terminator zone right and i think like you said i think your your first guess is is pretty much a good starting point that you have this kind of transition from redder back to kind of the dark zone um but there's a lot of variability there right whether it's starving for light and needs to just absorb it better or it has too much and it needs to regulate i would expect to see all of the above right it would adapt just like you said yeah that's great you know that's that's good that i would you know i felt like i was on the right track i think it's exactly on the right track yeah but even still that's just the best we can predict based on the information and understanding we currently have ultimately we only have a single point of reference our own planet earth and make as many models and deductions as we'd like there's no way to know for sure what life may look like in environments that we have no clear analog for well then what was the point of all of this why bother trying to figure out any of this in the first place what does it matter well as it turns out m-type stars are by far the most common kind of star we've observed making up an estimated 75 of all the stars in the milky way galaxy so yeah while we're talking about kepler-186f the significance of this debate is far greater in scale what we're really asking is what's the most common form of life in the universe knowing if life is possible and what it would look like in an environment like this lends us insight into the strategies and adaptations that could be used across countless alien worlds if in the end we come to the conclusion that life itself is unlikely to exist around red dwarfs well guess what that saves us so much time by eliminating three quarters of all the possible places to look and if they can support life well then even better it should be even easier to find either way with a scope as big as the entire universe it really helps to know where to look and what colors to look out for hey everyone i hope you enjoyed special thanks to nathan gaber for taking the time to zoom with me and answer some of my questions unfortunately i wasn't able to include everything that we talked about in the video so if you want to see our full conversation i'll be posting it on patreon also if you want to read the paper that he was a part of that'll be in the description i'm sure some of you noticed that this video took a little longer to make than the past ones and that's because i had to take some time off for family and travel something that's only possible because of my patrons if you'd like to be part of what allows me to keep making videos there should be a link right here to take you to my patreon other than that you know the drill like the video subscribe if you haven't already and i mean come on you watch this all the way to the end you might even want to hit that notification bell thanks

Channel: Atlas Pro

Views: 328,841

Keywords: education, geography, science, atlaspro, space, universe, galaxy, planet, moon, star, sun, exoplanet, kepler, red, earth, alien, plant, spectrum

Id: TgGoW5AIKEY

Length: 28min 58sec (1738 seconds)

Published: Fri Jul 23 2021

Reddit Comments

[u/Inignot12]

Atlas Pro is a really great channel, very cool geologic/geographic history and science stuff.

[u/sharkbiscut]

That was awesome! Great resource! Thanks for sharing!

[u/CosmoFishhawk2]

My current project has green plants. Though I do have a couple of future ideas that would work well with other plant colors.