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All pictures are taken from open sources and belong to their authors
The possible population of atmospheres of the giant planet
and the acid clouds of Venus – by the protozoans – is frequently written about.
However, the conditions on the planets of the Solar System are too harsh. It
is more interesting to consider a hypothetical planet – with moderate temperatures,
oceans and even an oxidizing atmosphere. And let’s assume that the density of
its atmosphere exceeds the Earth’s one by 100 times.
This assumption, by the way, is quite non-trivial. It’s not too clear where
to get enough nitrogen from, so more affordable carbon dioxide is likely to
be the basis of the planet’s atmosphere. Accordingly, there will be a powerful
greenhouse effect. But if you place the planet at a reasonable distance from
the sun, it will only benefit.
Nevertheless, the assumption deserves to be made, because it generates a special
world, fundamentally different from the earthly one, in which a hydrogen-filled
balloon capable of lifting a human will have a diameter of only one meter. And
this means that the flying jellyfish, beloved by science fiction writers, will
have the right to exist. Aerostatic flight will become the most obvious and
effective way of movemet, quite accessible even for creatures with hard shells.
In a world where air is only 15 times lighter than water, flying cavities in
animal bodies will be as common as swimming bladders in fish. But of course,
plants will be the first to take advantage of aerostatic flight. If the stem
filled with light gas does not weigh anything, then its height is practically
unlimited. The tree can stretch upwards for hundreds of meters, and even for
kilometers, to raise its crown, made not of flat leaves, but of bubbles, above
the clouds. After all, a dense atmosphere reluctantly transmits the light necessary
for photosynthesis.
Like algae, the trees of such a planet will keep an upright position due to
the lifting force of gas bubbles, and not due to the rigidity of the trunk.
The floating branches will be connected to the root system by a strong and flexible
harness having minimal windage and able to withstand a hurricane. Although,
there should be no conditions for the occurrence of storms on such a planet,
since temperature differences are small. But the density of the air compensates
for the low speed of movement of atmospheric masses.
If it is difficult to hold on to the soil, then why not leave it forever? Water
can be extracted directly from the air by spreading a web of roots, as some
orchids do. However, the plant will have to extract the necessary minerals from
rainwater and dust. But terrestrial lichens are quite content with these sources.
Here, the “prey” will be much more abundant. After all, small particles of wind-blown
soil and ash effluented by volcanoes will deposit in a dense atmosphere almost
as reluctantly as mud in water. The flying tree will only have to draw in the
grains stuck to the leaves, transport them by streams of sap into the “reactor”,
and dissolve them, as the mentioned lichens do.
It is possible to imagine greenish clouds of unicellular plants floating in
the atmosphere of the planet, but not on droplets of fat, as in the sea, and
on bubbles of hydrogen or methane, or simply gliding like little spiders do
on their webs. Or there are whole flying islands – colossal carpets of intertwining
hollow stems and leaves trailing in the wind. At sunset it is better not to
stand under such a drifting crown, because it is not profitable for plants to
carry the accumulated dust for a long time. The slag, from which everything
useful has already been extracted, must be discarded. It is more reasonable
to get rid of the ballast when the sun, which heated the shell, has set, the
gas cools and the lifting force decreases.
Animals will also have to adapt to life in a dense atmosphere. On the one hand,
the environment creates a lot of resistance to movement, and on the other hand,
it does not provide sufficient support. It is too difficult to run, and it is
still impossible to swim. Of course, insects can glide on tiny planes, in the
hope that air currents will bring them to food. Large creatures will have to
invent something original.
Everyone will have to fly. Even if the surface of the planet is not covered
by a bottomless ocean and is not overheated – in fact, it turns into the “bottom”
of the air sea. Biomass is created in the atmosphere, at an altitude where there
is enough light for photosynthesis. It will be consumed in the same place. Those
who didn’t take off will get only the leavings.
The optimal solution for these conditions will be a streamlined fish-like creature,
90% of whose body volume will be occupied by gas-filled cavities. Fins can be
useful, rather, as rudders, and the jet “engine”, like at squid, is preferable.
The size of the creature can range from large to colossal. After all, when swimming
in the air, as well as when swimming in the sea, the mass of the animal will
be limited only by available food resources. The most important is, that gigantism
improves the ratio of mass to the surface of the body, which is very important
for an almost “hollow” creature. The larger it is, the easier it is for it,
for example, to afford the replacement of soft coverings with hard calcareous
armor, impervious to gas and impregnable to enemies. Finally, the flying sperm
whale will be ten times larger than the sea-dwelling one, just because it is
inflatable.
It will not always be convenient for medium-sized animals to acquire aerostatic
organs. A hydrogen bubble will reduce speed and maneuverability, especially
vertical one, unless you blow it off completely when diving. This means that
flapping wing flight and gliding will remain common modes of locomotion.
Indeed, the pressure will drop with altitude. At twenty-five kilometers from
the surface, it will already be only ten atmospheres. There may be winds here
– quite strong ones, but a creature carried away by a mass of air will not feel
them and, moreover, does not risk run into an obstacle. The area is good for
plants; less water and dust, but greater amount of light. If it’s cold, the
dark covers, heated by the sun’s rays, will help.
The main thing is that it is more difficult for gliding insects and levitating
herbivores to get here. The creature weighing a kilogram will have to be a bubble
with a diameter of two footballs. The cavities will already occupy 99% of its
volume. For a plant, such a structure is acceptable. For an active and complicated
being, it is unlikely. At a higher altitude – up to fifty or sixty kilometers
– “living gliders” with impressive planes and arthropods on cobwebs can only
fly for a while. However, nothing will prevent both of them from resting and
even settling on floating trees.
Translated by Pavel Volkov, 2021
The original Russian article is here
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