13
$\begingroup$

Suppose that there is a moon, orbiting a gas giant, and that gas giant is a rogue planet - it moves freely through the universe, unbound by the gravity of a star. This means that one, the moon will never see the light of day, and two, there will be no sun to warm it.

But say that the processes of volcanism, convection and tidal heating do give it warmth. In that case, the moon could, potentially, be habitable, assuming other figures, statistics and technicalities were also appropriate for habitability.

With no light - save for naturally occuring fires or volcanic eruptions - photosynthesis is impossible here. Chemosynthesis isn't really possible except in special locations, so to have something roughly similar to plants, a new process must be devised.

We'll call that process kinetosynthesis - a method of autotrophy not seen on Earth. While photosynthesizers use chloroplasts to strip electrons from substances as water, kinetosynthesizers use piezoelectric crystals in their cells, such as quartz, to do the same thing, but with mechanical stress replacing sunlight. I'm no chemist, so I'll leave the process as vague as is for this question.

These kinetotrophic plants would likely have a number of energy sources, so as to exploit vacant niches; namely wind, rain, tides, sound and pure stress. If this sunless moon was volcanically active, wind and rain could be present - volcanic hotspots create contrasting hot and cold areas for the air to move between, and volcanoes play a part in Earth's water cycle - were they in greater density, they could cause rain to occur.

One possible problem with kinetosynthesis is the lack of energy that can be obtained - but perhaps the lower gravity, plus an oxygen-rich atmosphere (Which could be boosted significantly once kinetotrophic "Embryophytes" evolved, which in turn would be fuelled by the high volcanic activity), would decrease the energy usage of various organ systems, combined with drastic tides and fast winds - would make it more plausible.

In the end, it's fair to say that we really don't know if kinetosynthesis would work. But, let's just say that it is here. Finally, onto my question: If there were sessile, multicellular kinetoautotrophs, using piezoelectricity in the method described above, how would they be structured?

Let me explain a bit more. Earth plants, as we all know, have roots in the ground, a stem, and leaves. Stems are, in part, for growing taller than your peers, and thus get more light than them. How might kinetotrophs grow to recieve more energy than the surrounding ones? Leaves are for photosynthesis, mainly. Would kinetotrophs benefit from specialized kinetosynthesizing structures?

Obviously, a plant that got energy from the tides would look different to one that got energy from the wind, and one that fed on rain would differ from one that fed on sound. For your answers, you can select any of the energy sources (Wind, rain, tide, sound, stress).

If you consider this premise implausible, please say so. If you deem the question in need of editing, please say so too.

$\endgroup$
  • 2
    $\begingroup$ Is the piezoelectricity/quartz a hard requirement, or can we do it with chemicals alone? $\endgroup$ – Dubukay Aug 24 '18 at 15:34
  • $\begingroup$ @Dubukay If you have a viable method of kinetosynthesis without the crystals, go for it. $\endgroup$ – SealBoi Aug 24 '18 at 15:39
  • 1
    $\begingroup$ THis is clever, but probably unecessary. To have a viable atmosphere the planet would need to generate tremendous volcanic heat (which is hard enough to believe without gravitational stresses, but...). So much volcanism that you would have ash and other chemicals constitute a major fraction of the atmosphere. Chemosynthesis would evolve far more readily than kinetosynthesis. Reducing volcanism to favor kinetosynthesis would result (IMO) in no atmosphere (the gases would all freeze). $\endgroup$ – JBH Aug 24 '18 at 15:51
  • $\begingroup$ @JBH Yes, good point. I hadn't thought about that, I'll be considering it a bit more. $\endgroup$ – SealBoi Aug 24 '18 at 15:52
  • 1
    $\begingroup$ On the other hand, if this were something in addition to more likely evolutionary processes (the majority of plants used chemosynthesis, but a minority used kinetosynthesis, something unique to your rogue planet), that would be both believable and cool. $\endgroup$ – JBH Aug 24 '18 at 15:52
4
$\begingroup$

I'm going to take a crack at this one, as 'non-earthlike-energy for native life forms on exoplanets' is something that has interested me ever since I found out about the life here on earth, around volcanic vents under the sea, that use the earth's own heat for energy instead of the photosynthesis cycle (something widely considered to be impossible before its discovery). I may add more after I read other's answers for inspiration, but here's what I have off the top of my head (Disclaimer that I have no scientific experience to back any of this on, beyond entry level college biology class, and my own layman's 'research' prompted by my curiosity):

Stress: I would expect this to be the most primitive form of life in this scenario, analogous to single-celled organisms here on Earth, and possibly the simplest of multicellular life. A fast spinning moon could allow single celled kinetoautotrophs to use the gravitational changes felt from the gravity of the planet, both in intensity and direction, as the source of the stress. The primary environmental factor they would need for this 'niche' would be a solid surface to live on, to provide a resistance force against the gravitational one. Evolution, from there in to multicellular organisms, could yield a structure similar to a sea sponge or moss clumps, spherical or semi-spherical except where in contact with irregularities in the surrounding surfaces, and with cells at the bottom adapted to take advantage of higher stressses (from the increased weight above them) at lower ranges of motion, while cells above adapted to lower stresses and higher ranges of motion. The next evolution would be more advanced structures on the bottom of organisms to grip the surface to prevent tipping over during growth, and thus avoiding ending up with the wrong specialized cells in the wrong orientations, and to extract nutrients more efficiently from the hard surface or any incidental liquid that might be present. Minor variations would exist for different climates. Wider and flatter in high wind areas or where flooding is a concern, taller and more conical in calmer areas. And that's where I think evolution would branch to adapt to more varied surfaces, and based on environmental conditions related to the other sources of energy, wind, rain, tides (sound adaptations come later).

Wind: To me, this seems like the first natural adaptation to an alternate form of kinetic energy, simply due to the fact that it would be so wide-spread across the surface of the moon, regardless of the presence or absence of standing, flowing, or falling liquid, and especially if my assumption (mentioned in my section on stress energy) of a fast rotation speed is accepted since this rotation would also cause (relatively, compared to slower rotation speeds) more or less constant winds with and high average speeds for winds. Structural adaptations for this would vary widely, depending on surface, and also depending on prevailing wind conditions like speed (fast or slow) and consistency (steady or gusty). For broken surfaces (gravel, sand, soil, etc) root-like structures would be likely, to help keep from being blown over, and to provide a stable foundation to allow the possibility of more and greater vertical growth. For more unbroken solid surfaces, I would expect a horizontal variation of what is seen on wall-climbing vine plants, a network of 'branches' sent out from the base to seek out any of the relatively rare nooks and crannies that could be used for anchorage, and also to simply provide a wide base for support in the absence of significant or sufficient anchor points in the surface itself. Now, on to the energy collecting structures. Simpler forms of life would have structures that appear, superficially, like blades of grass, or a very short stem (stems with wide separation if multiple are present in a single organism) with a single leaf-like or fan-like (like an accordion-folding fan) structure at the end of each stem. The grass-like blades (more common in steady winds) could be air-foil shaped (think an airplane wing tipped up verticle) causing a bending motion (and subsequent stress for energy) in response to the wind, or have a cross section shaped like the letter "C" so that as wind fills the gap it will spill out of one side, causing a twisting motion (and subsequent stress for energy) before rebounding and catching more air which spills out the opposite side, oscillating it back and forth repeatedly (like a ribbon pulled semi-tight in stiff breeze). Fan structures (more common in areas with more calm air and intermittent stronger gusts or windstorms) could vary more widely, portions of a circle (nearly full circle, semi circle, quarter circle) for maximum surface area with minimal mass to take advantage of every slight change in the air movement in regions of low prevailing wind speeds and low intensity/frequency gusts and low intensity/frequency windstorms, to more exotic variations like very thin and fibrous webs (like dandelion fluff, but in any and all shapes) or a 'kite' with a horizontally oriented airfoil shape at the top of the stem to intentionally 'lift' and stretch the stem. More advanced varieties would evolve other ways to increase their surface area impacted by the wind, and increase strength (probably through thickness) of stem (trunk) and anchorage to withstand the compounded forces received by the additional impacted surface area. To do this, many would literally branch out like earth trees except that on earth optimum branching direction is perpendicular to the direction of sunlight (which averages to vertical from the surface of the earth, causing branching horizontally, causing plants to generally have a round shape when viewed from the top down) while optimal branching direction for wind gathering plants on this moon would be perpendicular to the prevailing wind direction, so they would generally branch north, south, and vertical, since prevailing wind direction would be either east to west, or west to east, depending on the direction of the rotation of the moon. So viewed from the top down, the branching plants would primarily look like long thin lines, slightly tapered at either end. Viewed from the north or south, they would again look long and thin, and tapered from top to bottom. Viewed from the east or west, they would most likely look like a rounded fan or semi-circle, or the very advanced ones might evolve strong enough anchors and trunks to make more significant vertical gains and look like a circle on the end of the stem/trunk. The advanced species that don't branch might evolve much wider bases perpendicular to the wind, and then fan out vertically, like giant versions of leaves. Others might send out long thin streaming threads from elevated branches to whip in the wind at the ends for maximum movement and energy gains. To compete with other organisms in the direct vicinity, any of these variations would likely use their base/root/anchor structures to seek out competition toward the prevailing wind direction, since any organism in 'front' of them (relative to wind direction) could block their source of energy, while organisms behind them would only be able to compete if they can also send something forward to 'attack' organisms. Once a competitor is identified, the organism behind would seek to either cut off the base or cover the face of the competitor. The most desirable reproduction strategies would be anything that sends offspring in the direction of the prevailing wind, so seeds in the air would be counterproductive, unless there is a band of suitable environment that is a complete circle around the moon (not likely). So budding up from anchors out in front of (though likely not directly in front of) the organism is a likely, creating colonies of organisms with members of a generation generally spread out north to south from each other, and members of newer generations in front of them, though staggered/offset north to south of the older generation behind them.

Rain: This one is the one I think is the most interesting. A quick Google search got me estimates of up to about 14% of Earth's land area was once (pre-deforestation) covered by rain forest. Adjusted however you like for the total land area (as opposed to ocean) of this moon, and it's still a relatively rare thing, and the highest frequency I could find for rainy days per year was 243, in Belem, Brazil, in the Amazon rain forest. That's almost exactly 2 days out of 3, in the place where it rains the most frequently that I could find (not the highest amount of water volume, but the most reliable rain). This makes rain a very unreliable energy source (in general, on a the scale of the entire surface area of a moon[planetary? scale {but it's not a planet} moon-itary scale?]), except in the most ideal climates. So this type of life, with adaptations for this energy source, would likely be both relatively rare and relatively isolated. I see simple life forms evolving from the sponge-form or mossclump-form bu sending out horizontal (Like the branching of trees and plants on Earth spreading horizontally to catch the vertical [by average] sunlight) appendages from a ring near the half way point(ring) between their base and their peak to catch the energy from the vertical (again, average) falling rain. Somewhere near halfway between top and bottom is because too low and there is no room for downward flex after impact from the raindrops, and too high and it would be pointing straight up and there would not be room for enough appendages making it hard to have enough surface area to catch enough rain to be useful. In intermediately advanced life, the spongy/moss base evolves in to a more specialized root/anchor structure, which spreads out more efficiently, either by flattening like a disc, or by separating in to a more branching network, and the appendages become more specialized as well, some becoming dedicated support structures (stems/trunks), while others specialize at catching and using the rain energy by either increasing in number while thinning out (think very long thin stiff grass growing sideways instead of vertical), or by forming wider leaf-like shapes. The more advanced would combine the two, having very small fuzzy hairlike structure on their leaves that would react to the flowing of the rain off of the leave after impact, while the larger leaf structure focuses on harnessing the energy of the impact itself. The most advanced appendages would be even more highly specialized, forming funnel shapes (complete with openings at the bottom) with their largest leaves, and lining the inside surfaces with fine hairs, creating artificial currents at the bottoms of the funnels so that collected rain could provide longer term energy as it flows slowly through the end of the funnel even after the rain has stopped. Competition with local organisms would lead to both horizontal (cover up the neighboring organism) and vertical (get high enough that you can cover the neighboring organism) adaptations. These would likely be the only 'true' 'trees' on the planet, though the only thing that might encourage any significant height would be the low gravity on the moon. If the gravity is not enough of a factor, then even these trees would be relatively short compared to earth's trees. Being covered up by a competing organism could lead to special adaptations to catching residual rainfall coming off the leaves of the organisms above, such as extremely large individual leaves funneling in to relatively complex and efficient funneling systems. Unfortunately, nothing specific comes to mind for reproduction specializations for this energy form.

Tide: I see two main methods here, sheer ocean surface level changes, and water flow changes like currents and waves. The adaptations for currents and waves are more likely to be more primitive than adaptations for ocean levels, because the immediate brute force of the waves are likely to have a more direct and immediately impactful influence on the sponge/moss close to the shoreline than a relatively calm and slow rise of the tide. The first adaptations would be the strongest anchoring system so far, to avoid being dislodged entirely and lost to the depths, and appendages to move with the flow of the waves and harvest energy from them. I see two main types of appendages forming here: the first is very stiff and strong, to take a beating from waves without breaking, while flexing just enough to create great internal stresses for energy collection. probably starting our as relatively straight spines like a sea urchin's, and later would be more complex lattices like fan coral but more flexible. The other would be VERY flexible, like fine strands of moss, or flowing kelp leaves, making use of movement by gathering less energy per movement, but making up for it by moving more often and in more directions. The most advanced species in this group take advantage of the tides directly. These are the ones that competed with the other wave dwellers originally, but got their start in the deeper side of the coastal waters and managed to survive despite being distanced from the most energetic areas of the waves nearer the shoreline. To avoid sinking too deep below the level where the wave movement wasn't sufficient, they developed gas filled bladders to keep their energy capturing appendages up nearer the surface where the wave energy is stronger. This increased pressure on their anchoring structures, leading to improved anchoring structures. This allowed access to increased depth while maintaining access to energy. This created a cycle of evolution, increased depth > increased bladder > increased anchoring > repeat. Eventually the depth achieved was so great, that sufficient wave energy was out of reach to support the nergy requirements of the stalk structure between the anchor and the energy capturing leaves. The next adaptation at this point was for the stalk structure itself to become an energy producer, from the stretch stress between anchor and gas bladder. Further adaptation moved this stress from secondary to primary, and the leaf structures become vestigial, or disappear entirely. At the same time, the anchor, stalk, and gas bladder all become exagerated until the most advanced species is an enormous bladder that floats on the surface of the ocean at low tide, and is mostly or completely submerged at high tide. This is connected to a very strong, thick, stalk which receives massive stress energy from the bladder pulling up and the anchor structure holding it down. Competition would be mostly based on surface area under the water, for anchor points, individual organisms would seek to cover as much of the available nooks and crannies within their reach, to ensure the best hold. I see no reason that reproduction in this oceanic environment would follow a pattern any different than earth's oceans, so budding/self-cloning, and releasing egg/sperm directly in to the water on regular cycles, are likely options regardless of the specific oceanic region or adaptation of the rest of the organisms body type.

Sound: This would be the most advanced individual adaptation of any of the groups, and would apply to all of them, from the sponge/moss to the wind, rain, and tide, types. In other words, the adaptation wouldn't be specific to any of the groups, but any species within the group that has this adaptation would be the among the most advanced species in their respective groups. This mechanism actually exists in the animal kingdom on earth, and the human inner-ear is a good example. It has hair-like structures (an adaptation I already mentioned for other types) that convert movement from sound waves to electrical signals. The sponge and moss clump species could directly produce these hairlike structures externally, and the sponges could also have them inside the cavities that already existed in their more primitive relatives. Wind-specialists could incorporate them on their surfaces as well, and the most advanced would be the ones with ancestors that had already specialized to have a higher number of leaves/appendages with smaller surface structures, thus allowing their more advanced descendants the benefit of having more surface points from which to generate those hairlike structures. Rain-specialists would probably evolve this adaptation before the others, as the movement of liquid inside confined spaces is already part of their initial strategy, so this would just close the loop for them. Tidal-specialists could sprout those hairs from any part of their structures, since they are (almost) entirely submerged (almost) all their lives. The massive bladders of the deepest tidal species could have those hairs both inside and outside the bladders, to take advantage of sound both through air above (at low tide) and below.

my own group: A hybrid type, not mentioned by the OP, seems likely to me. If it rains, and there are oceans, then there are almost certainly rivers that take the rain back to the ocean. Specialist species, hybrids(in form if not literally) between rain/wind/tidal, could anchor to the banks of rivers(easier to anchor on land, where water isn't trying to rush the seedling away from any anchor points), and reach appendages in to the current where they act like a combination of wave/wind energy collector appendages. Advanced variations could still use funnel forms like the rain collectors, but submerged. The Sound collecting hairs would not function on 'sound', specifically, while submerged as the current of the water would likely be universally more efficient than sound collection in this environment, but the surface structures could use them.

$\endgroup$
  • $\begingroup$ A brilliantly comprehensive answer. Thanks for putting in so much thought. $\endgroup$ – SealBoi Sep 15 '18 at 7:20
7
$\begingroup$

There should be a part of the plant that, as much/as often as possible, is rhythmically moving.

Kinetosynthetic organisms would depend on relative motion between different parts of the their body, and their evolution would seek to maximize the amount of relative motion they obtain from the environment. I would expect your plants to end up looking like organic versions of machines that we have for harvesting energy from motion.

Concept organisms that come to mind:

Windmill plant: "leaves" that are shaped such that they flap back and forth or make circular motions in the wind, at the top of a stalk that holds them up from the ground for better airflow.

Wave-energy plant: Attached to a shore/coast/riverbank with a floating part on the water, bobbing in the waves; kinetosynthesis occurs in the rhythmically bending stalk. (See here: https://www.youtube.com/watch?v=GA_UgVm9bvU )

Wave-energy carpet plant: a floating carpet on wavy water (perhaps anchored with stalks to the river/ocean floor), with stretchy fibers above and below the floating volumes. As the carpet ripples in the waves, the stretchy fibers are rhythmically flexed.

Wind/current energy grass: simply a flexible blade/stem shaped so that it bends/twists in the wind (above water) or in the current (in a river).

In general: for the plant to be viable, it needs a systematic source of rhythmic motion. What part moves? How does it maximize the motion?

Final note: as these plants compete to capture motion out of the environment, they will slow/deaden the motion surrounding them. If enough wave-energy plants grow around a shoreline, they will eventually clog and deaden the wave motion there and reach an equilibrium where some are dying for lack of energy. (You could have predators/scavengers clear out the dead ones faster than they accumulate, though...how you manage your ecology is up to you!) Just keep in mind that plants will tend to congregate and saturate regions with high relative motion, like riverbanks or windy hilltops.

$\endgroup$
  • 2
    $\begingroup$ As far as photosynthesis evolved on Earth , single-celled plants were the pioneers. How do you think a similar evolution with kinetic energy began without having to skip that essential phase? $\endgroup$ – Christmas Snow Aug 25 '18 at 19:29
  • 1
    $\begingroup$ A good question! If I were going to try to come up with an evolutionary path, I would try to find an intermediate organism that is initially chemosynthetic but that benefits from environmental motion. I suspect that any movement that oscillates an organism (or part of an organism) up and down a gradient of chemical concentration - this would be a potential intermediate between chemo- and kinetosynthesis. $\endgroup$ – Qami Sep 14 '18 at 21:21
3
$\begingroup$

Earth's photosynesizing plants come in all shapes and sizes

Which makes it difficult to predict what a kineteosynthesizing plant would look like. Earth's plants come in all densities, all configurations, all flexibility and rigidity. There are so many factors that go into estimating the evolution of plants that, IMO, this is a nearly impossible question to answer.

Nearly....

Energy or the resources to convert to energy must be obtained from somewhere. Earth's plants generally obtain said resources from two directions: the soil and the sun. Soil resources (water & chemicals) come through roots. Sugar comes from the chemical processes of photosynthesis, which requires sunlight.

And that means capturing the sun. Whether through leaves or from the surface of stalks, sunlight impacts the plant, which enables the plant to convert soil resources into sugar for energy.

The kineteosynthesis idea is interesting, but what's the external resource it's using to create sugar?

Your plants will still have roots and still obtain most of their resources via soil. There's no sunlight (though there is some light generated from the planet's volcanism). As mentioned in my comments, there's plenty of chemical abundance in the atmosphere, so chemosynthesis is likely — but that's not your question, so we'll ignore it.

That leaves vibration, caused by the volcanism.

  • A plant that lives in a high-vibration environment needs stability. That would suggest either very, very deep roots or a vast array of micro-roots such that the plant and the soil it depends on will stay in place.

  • Earth's plants survive high winds just fine, so I don't believe there would be a specific structure to help your plants survive high vibrations, but we could assume a thicker or more dense epidermis layer. I could imagine one of your plants adapting to its environment by incorporating the atmospheric ash with a thick ooze exuded from the epidermis resulting in a flexible but epoxy-like surface that protected it from the consequences of vibration.

  • We have a precedent for using piezoelectronics to generate electicity in the form of vibration powered generators. The plant would need sheets of piezoelectric crystals that, basically, move back and forth like a speaker membrane. The motion causes electricity via the piezoelectric crystals which could replace sunlight as the glucose-creating catalyst. I can imagine flower petals taking on this role.

But in the end, the actual look of your plants is up to you

Earth has proven that plants can take on so great a variety of looks that it's quite literally impossible for us to tell you what your plants will look like. Honestly, they'll look like the plants we have other than they won't generally be green. Whether they have leaves will be dependant on your environment, whether or not flowers have color will be dpeendent on your ecology. It's horrifically complex.

But, I've come up with three consequences of your world that would/could impact plant development: root structure, epidermis structure, and the membranes needed for electricity generation. You can take if from there.

$\endgroup$
2
$\begingroup$

Since kinetosynthesizing structures need to move, flex or stretch to produce energy, evolution would favor light and flexible structures that move at the slightest provocation.

One possible branch of evolution would look like a fan coral and consist of very soft, lightweight branches that can all move individually. That way the plant catches the slightest movement of air or water around it and produces energy not only from the original current, but also from vortexes caused by its own shape. It has the disadvantage of being very vulnerable to strong currents.

Those places with constant strong currents could be populated by plants shaped like long leaves of grass. Either seperate leaves grow directly out of the soil or some plants develop stronger, inflexible stems to lift their leaves above ground to catch more currents. If a current is strong enough to affect the whole length of the leaf, it will put it into a wave-like motion. Lots of movement, lots of energy harvested. But these are vulnerable to times of calm winds or currents and need a way to store excess energy.

Tumbleweed could also produce piezoelectric energy by tumbling around. The spheric structure moves well at the slightest current, is resilient to too strong currents and beeing backed into a corner only increases the deformation and thereby energy production.

You could even create a plant that can thrive without much of an atmosphere, as volcanic ashes rain down to the surface due to gravity alone. This one has very thin, lightweight leaves like overlong grass blades. They grow at a 45° angle upwards and form a slight curve. They are also covered with a dust repelling lotus-effect surface. The ashes constantly raining down from volcanoes accumulate on those leaves and bend them, producing energy. If a certain mass of ashes accumulated, it slips off the surface and the process starts all over again. Since the plant would be buried in ashes sooner or later, it must constantly grow longer, opening up a second opportunity to produce energy.

The strong gravitational forces cause not only tidal heating, but also tidal deforming. A truely long blade of this pland might harvest energy from being stretched, bend and compressed by the ever shifting gravitational tides.

$\endgroup$
0
$\begingroup$

I'm almost certain this is nearly impossible, but in good faith I'll go with it on the small chance it isn't.

Kineticsynthesizers would probably all take on flat, wide shapes. I'd imagine them starting out as colonies of single cell organisms that coat surfaces which eventually evolved into multicelled organisms with the same traits. Since the multicellular versions would produce more energy and have more chances at nutrients they would fair slightly better than their colonial counterparts.

I imagine tidal versions pressed against cliffs would fair well, the compression of water and rock being a good medium for kinetic synthesis, and the nutrients from the water being good for growing. Tides probably wouldn't be regular on a drifter, but because pressure travels well through water sources like earthquakes and landslides would effect the water as well, plus possibly dump the chemicals life needs into it.

A wind version could also grow on cliffs that are buffered by winds, but they could be scoured off by strong winds with particles so maybe not.

I can't think of a scenario where sound or stress are consistent or loud enough for this to work.

Rain may work, same with tides or wind, but I'm again not sure if the rain generates enough pressure, though there's a fair chance of it being consistent enough somewhere, though maybe you dont get rain on a planet with no sun for evaporation. Maybe occasionally.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.