While I cannot say that such an organism is impossible, here are a couple obstacles that it would need to overcome:
Sparse nutrient availability—In the ocean, phytoplankton growth is primarily gated by the available nutrients in the water column (particularly phosphates, nitrates and iron compounds, in addition to oxygen iirc). Air has significantly less capacity to transport nutrients compared to how nutrients in the ocean can be both dissolved in water and present in particulate matter.
Sub-optimal temperatures—Even at the equator, the atmospheric temperature rapidly drops with altitude, with averages quickly falling below those favorable to most algae.
What biological mechanism would it use for efficiently staying permanently aloft?
...Aww hell. Am I starting to write like an LLM or do LLMs these days write like me?
Spanish moss is able to scavenge sufficient nutrients from the air/water without needing direct contact with soil, but it is also useful to note that the water it gets is able to dissolve more nutrients as it comes in contact with tree branches and airborne particles, which are more abundant closer to the ground. I predict it would struggle to do the same even one or two kilometers higher, even if it was warm enough up there (it’s not).
It is also notable that many species of algae and moss do use airborne spores to successfully spread themselves around the planet. Spores are typically dormant until certain conditions are met & I do not know of any that grow and actively metabolize while airborne[1]. If air, rain, and light were the sole factors at play I would expect to see more things like Spanish moss growing from the ledges of lofty skyscrapers. Though a few niche plants have adapted to extremes in elevation and temperature they are the exception rather than the rule and are far less numerous than their more down-to-earth counterparts.
TL;DR: While it is technically possible for highly specialized plants to survive in some of these conditions, it is an unforgiving environment that is less favorable for photosynthetic life. Rather than the proverbial low-hanging fruit left untouched, the high-floating fruit has been tasted and found rather cold and bitter for most tastes.
I am not an expert, but I have a general familiarity with algae and plant life cycles.
I would love to be wrong here, if they did exist I would still expect them to fly over the radar for a while before humans look closely enough to discover them
Claude did in fact give a similar answer! The thing is though, it seems to me that there’s a big difference between “super difficult” and “impossible.” There are lots of extremophile organisms that have adapted to all sorts of crazy conditions. All it takes is for one of them to adapt to being airborne, sometime in the five billion years of earthly history, and bam, there they’d be thenceforth, with no predators.
I would love to see it happen. It’d be nice to have more stuff in the air removing Co2 and absorbing sunlight. I’m curious, what got you thinking of floating algae?
I would estimate the relative difficulty of [colonizing Himalayan mountain slopes vs free-floating (pelagic?) life at a similar altitude] to that of [adapting to the salinity of the Great Salt Lake, vs that of the Dead Sea]. The former can support brine shrimp and microorganisms, the latter only microorganisms. Equivalently, the slopes can support simple multicellular life on down, while in the atmosphere we’ve found bacteria and little else so far.
We know there are particular points at which it is ~impossible for life as we know it to survive e.g. inside the sun, but less extreme absolute lines seem to tempt evolution.
I wonder if sufficient intelligence could distill a formula for estimating likelihood of life adapting to arbitrary parameters in a particular time frame? Like: “given certain resources and conditions, viable adaptations might form in x [millon/billion] years.”[1] Then it would simply be a question of “will these conditions last long enough for the adaptation to happen with a high probability?”
But then again, would that require it to brute-force simulate ~all possible mutations for a certain number of steps? And at what point is the simulated life behaviorally indistinguishable from the physical? Obviously I’m out of my depth and far from my expertise here but it sure is fun to speculate
One way to tell that you’re at the edge of viability for actual living at this point, as opposed to simply passing through or enduring it until better conditions arise, is that Antarctic mountain slopes appear to be completely sterile and free of microbes:
We analyzed 204 ice-free soils collected from across a remote valley in the Transantarctic Mountains (84–85°S, 174–177°W) and were able to identify a potential limit of microbial habitability. While most of the soils we tested contained diverse microbial communities, with fungi being particularly ubiquitous, microbes could not be detected in many of the driest, higher elevation soils—results that were confirmed using cultivation-dependent, cultivation-independent, and metabolic assays. While we cannot confirm that this subset of soils is completely sterile and devoid of microbial life, our results suggest that microbial life is severely restricted in the coldest, driest, and saltiest Antarctic soils. Constant exposure to these conditions for thousands of years has limited microbial communities so that their presence and activity is below detectable limits using a variety of standard methods.
Presumably if you brought microbes there, they would be able to endure for a while (and given aerial dispersal, they must be arriving constantly). But apparently no meaningful form of sustainable life at the microbial scale or higher is possible. (Similar to bacteria, spores, or tardigrades being able to survive exposure to space, and thus hitchhike to other planets or cause panspermia—but can’t actually grow, reproduce, or even just sustain a constant population in space.) Air might be similar: not so much because of the horrible salts in air, as its general lack of moisture and, well, everything else too.
So air can be a great medium for dispersal (as it is for even larger organisms like spiders), and there’s evidence about bacteria manipulating weather for this purpose, but it’s no place to live for biological life as we know it.
(Which of course says little about mechanical life: they don’t necessarily need any water, they can engage in complex logistics to move around atoms that they need like piping feedstocks up into the sky, they can create structures which bacteria would be utterly unable to like kites supporting solar panels or mirrors, they can use it bacteria-style for covert dispersal and do heavy industry on the ground, etc. They aren’t selfish little replicators which must evolve tiny fitness-incrementing step by step from little blobs of self-bootstrapping organic goo solely to maximize reproductive fitness under constraints of heavy predation & defection, among other limitations.)
If you can secrete the right things, you can potentially cause rain/snow inside clouds. You can see why that might be useful to bacteria swept up into the air: the air may be a fine place to go temporarily, and to go somewhere, but like a balloon or airplane, you do want to come down safely at some point, usually somewhere else, and preferably before the passengers have begun to resort to cannibalism. So given that even bacteriophage viruses are capable of surprisingly sophisticated community-wide decisions about when to kill their bacteria hosts and find greener pastures, and that bacteria communities can do similar calculations about dispersal or biofilm formation, it would not be too surprising if bacteria in a cloud storm might be computing things like timers or counting the average rate of organic matter floating upwards, to decide when to ‘try to land’ by everyone secreting special ice-nucleating molecules in the hopes of triggering the storm that will deliver them safely to the foreign ground, rather than waiting passively for a random storm which might put them down too late or somewhere bad.
While I cannot say that such an organism is impossible, here are a couple obstacles that it would need to overcome:
Sparse nutrient availability—In the ocean, phytoplankton growth is primarily gated by the available nutrients in the water column (particularly phosphates, nitrates and iron compounds, in addition to oxygen iirc). Air has significantly less capacity to transport nutrients compared to how nutrients in the ocean can be both dissolved in water and present in particulate matter.
Sub-optimal temperatures—Even at the equator, the atmospheric temperature rapidly drops with altitude, with averages quickly falling below those favorable to most algae.
What biological mechanism would it use for efficiently staying permanently aloft?
...Aww hell. Am I starting to write like an LLM or do LLMs these days write like me?
Spanish moss is able to scavenge sufficient nutrients from the air/water without needing direct contact with soil, but it is also useful to note that the water it gets is able to dissolve more nutrients as it comes in contact with tree branches and airborne particles, which are more abundant closer to the ground. I predict it would struggle to do the same even one or two kilometers higher, even if it was warm enough up there (it’s not).
It is also notable that many species of algae and moss do use airborne spores to successfully spread themselves around the planet. Spores are typically dormant until certain conditions are met & I do not know of any that grow and actively metabolize while airborne[1].
If air, rain, and light were the sole factors at play I would expect to see more things like Spanish moss growing from the ledges of lofty skyscrapers.
Though a few niche plants have adapted to extremes in elevation and temperature they are the exception rather than the rule and are far less numerous than their more down-to-earth counterparts.
TL;DR: While it is technically possible for highly specialized plants to survive in some of these conditions, it is an unforgiving environment that is less favorable for photosynthetic life.
Rather than the proverbial low-hanging fruit left untouched, the high-floating fruit has been tasted and found rather cold and bitter for most tastes.
I am not an expert, but I have a general familiarity with algae and plant life cycles.
I would love to be wrong here, if they did exist I would still expect them to fly over the radar for a while before humans look closely enough to discover them
Claude did in fact give a similar answer! The thing is though, it seems to me that there’s a big difference between “super difficult” and “impossible.” There are lots of extremophile organisms that have adapted to all sorts of crazy conditions. All it takes is for one of them to adapt to being airborne, sometime in the five billion years of earthly history, and bam, there they’d be thenceforth, with no predators.
I would love to see it happen. It’d be nice to have more stuff in the air removing Co2 and absorbing sunlight.
I’m curious, what got you thinking of floating algae?
I would estimate the relative difficulty of
[colonizing Himalayan mountain slopes vs free-floating (pelagic?) life at a similar altitude] to that of
[adapting to the salinity of the Great Salt Lake, vs that of the Dead Sea]. The former can support brine shrimp and microorganisms, the latter only microorganisms. Equivalently, the slopes can support simple multicellular life on down, while in the atmosphere we’ve found bacteria and little else so far.
We know there are particular points at which it is ~impossible for life as we know it to survive e.g. inside the sun, but less extreme absolute lines seem to tempt evolution.
I wonder if sufficient intelligence could distill a formula for estimating likelihood of life adapting to arbitrary parameters in a particular time frame?
Like: “given certain resources and conditions, viable adaptations might form in x [millon/billion] years.”[1]
Then it would simply be a question of “will these conditions last long enough for the adaptation to happen with a high probability?”
But then again, would that require it to brute-force simulate ~all possible mutations for a certain number of steps? And at what point is the simulated life behaviorally indistinguishable from the physical?
Obviously I’m out of my depth and far from my expertise here but it sure is fun to speculate
One way to tell that you’re at the edge of viability for actual living at this point, as opposed to simply passing through or enduring it until better conditions arise, is that Antarctic mountain slopes appear to be completely sterile and free of microbes:
Presumably if you brought microbes there, they would be able to endure for a while (and given aerial dispersal, they must be arriving constantly). But apparently no meaningful form of sustainable life at the microbial scale or higher is possible. (Similar to bacteria, spores, or tardigrades being able to survive exposure to space, and thus hitchhike to other planets or cause panspermia—but can’t actually grow, reproduce, or even just sustain a constant population in space.) Air might be similar: not so much because of the horrible salts in air, as its general lack of moisture and, well, everything else too.
So air can be a great medium for dispersal (as it is for even larger organisms like spiders), and there’s evidence about bacteria manipulating weather for this purpose, but it’s no place to live for biological life as we know it.
(Which of course says little about mechanical life: they don’t necessarily need any water, they can engage in complex logistics to move around atoms that they need like piping feedstocks up into the sky, they can create structures which bacteria would be utterly unable to like kites supporting solar panels or mirrors, they can use it bacteria-style for covert dispersal and do heavy industry on the ground, etc. They aren’t selfish little replicators which must evolve tiny fitness-incrementing step by step from little blobs of self-bootstrapping organic goo solely to maximize reproductive fitness under constraints of heavy predation & defection, among other limitations.)
Sorry, what?
Ice-nucleating bacteria: https://www.nature.com/articles/ismej2017124 https://www.sciencefocus.com/planet-earth/bacteria-controls-the-weather
If you can secrete the right things, you can potentially cause rain/snow inside clouds. You can see why that might be useful to bacteria swept up into the air: the air may be a fine place to go temporarily, and to go somewhere, but like a balloon or airplane, you do want to come down safely at some point, usually somewhere else, and preferably before the passengers have begun to resort to cannibalism. So given that even bacteriophage viruses are capable of surprisingly sophisticated community-wide decisions about when to kill their bacteria hosts and find greener pastures, and that bacteria communities can do similar calculations about dispersal or biofilm formation, it would not be too surprising if bacteria in a cloud storm might be computing things like timers or counting the average rate of organic matter floating upwards, to decide when to ‘try to land’ by everyone secreting special ice-nucleating molecules in the hopes of triggering the storm that will deliver them safely to the foreign ground, rather than waiting passively for a random storm which might put them down too late or somewhere bad.
I started thinking about it because of thinking about Yudkowsky’s old idea of diamandoid nanobots replicating in the upper atmosphere.