Bacterial Flora

These macroareonts, which have been christened Pocupoa, have only recently been discovered around temperate mountain streams leading from Hadriacus Mons into the Hellas Basin. They are perhaps among the most wonderful creatures, for they are multicellular, centimetre-tall prokaryotic organisms. Multicellular prokaryotes do exist on Earth as well, in the form of myxobacteria and some blue-green algae, but none have ever been observed growing to this scale. Pocupoa are characterized by having a rigid and porous outer shell and either an internal layer or spicule skeleton, all made from silicon dioxide, similar to diatoms. Most of the body is made up of this skeleton or hollow, water-filled spaces, with the actual living cells only making up a small amount of the volume. How exactly these organisms work is still being debated. On Earth, multicellularity in prokaryotes is usually associated with harsh living conditions and nitrogen starvation. When lacking enough nitrogen, cyanobacteria-filaments will form special cells called heterocysts which do not participate in photosynthesis but are instead surrounded by the other cells of the body to create anaerobic conditions under which the heterocyst can better fix nitrogen from the air or water. On Mars, nitrogen makes up only 3% of the atmosphere, so such organisms would be under a constant state of nitrogen starvation. It seems very likely then that these primitive cells have become permanently multicellular to combat these conditions through teamwork. The siliceous shell structure has likely evolved to both help separating photosynthesizers from nitrogen-fixers, as well as creating anoxic conditions inside the body for the nitrogen-fixers. In addition to these two cell-types, there also seem to be cells dedicated towards building and holding together the structure. Despite this specialization into different cell-types, Pocupoa do not possess genuine tissues, as every cell seems to be capable of morphing into a different type when the need arises, a condition that can also be seen in sponges.

Several types of Pocupoa have been identified, though we do not know if these are genuinely different families or simply a variety of morphs the colonies can assume. The most common type are the Durupoa, which have a tube-like build. In the Acupoa, the tip instead consists of an ornate cap resembling the Kremlin-towers. In the Sporopoa, the cap is formed into a mushroom-like hood, potentially to protect the soft fruiting-bodies underneath. In the Scutrapoa the hood seems to be inverted into a bowl, for reasons unknown. Sporopoa interestingly seem to be the only members who reproduce through wind-carried propagules. Most other types instead seem to go for a stolon-based reproduction, as their bases form long-winding, thin roots both above and underground that interestingly connect both with conspecifics and other types of Pocupoa. While all of these organisms likely reproduce asexually, it is not unthinkable that horizontal gene-exchange between individuals might occur through these networks.

Some role of the Pocupoa in the Sulphur-Cycle is also suspected, though what role is uncertain. The assumption stems from close association of these organisms with Cochleophyta, which are corkscrew-shaped plants and among the most primitive of the Arephyta, as they lack symbiosis with sulphur-reducers and therefore require free hydrogen sulfide in the environment.

Direct interactions between animals and Pocupoa have not been observed so far. Most seem to either ignore them or in some cases even avoid them.

Yrp

The Yrp is a common, though quite unusual member of the Onychognatha, about the size of a kangaroo mouse. It is part of the more “primitive” Archaeocephalia, but still differs dramatically from the typical body plan. The jaw-limbs have lost their opposing finger and have instead becomes horizontal mandibles like in an ant. Furthermore, two more of the post-oral segments have shifted towards the skull and aid now in feeding, while the body is now entirely carried by the hindmost, almost birdlike and incredibly long legs with digitigrade feet. The antennae have also retracted into the skull to form sensory pits. Despite its erect stance, the Yrp is an ectotherm, as in the benevolent Martian gravity such a body posture can be maintained even with lower metabolisms. Yrps use their impressive, though crude jaw apparatus to feed on the bodies and appendages of succulent fractarians, as well as soft sporians. It is hunted by various onychognaths, verticutian spirifers and species of Hortax.

What the prominent bony protrusions on a Yrp’s back are for is not known. Some form of social display is likely. It has been discovered, by complete accident, that they seem to have spots only visible in ultraviolet, though it is unknown if yrps can actually see in that part of the spectrum. It also has been proposed that the increased surface area might help the Yrp fill up more of the faint Martian sun’s heat in the early morning hours, though one would think that an actual sail would be more practical for that purpose.

The intelligence of yrps is currently a debated question. The small brain size would suggest reptilian or even insectoid levels of cognition, but in a particular case a single yrp was once observed looking at itself in the reflective wheel rim of our Mars buggies, deliberately using its mirror image to scratch off a bit of dust behind its left eye. This seems to have been an anomaly, however, as in no subsequent controlled attempt has any yrp ever passed the mirror test or similar cognitive assessments. Thus, the search for intelligence on Mars continues. We better find it soon, because there is bugger all down there on Earth.

Ifrit and Tynus

The Ifrit on top and the Tynus at the bottom are both members of the phylum Onychognatha. Onychognaths are the arezoans which in morphology come closest to Earth’s vertebrates, as they are bilaterally symmetric and possess an endoskeleton and spine of apatitic (though sometimes also siliceous) make-up. Though this is usually as far as similarities go, as many of the body forms these animals assume have more of a resemblance to arthropods and in their very bony heads there is little room for much of a brain. Phylogenetic bracketing indicates that the ancestor of this clade likely was a worm-like animal with a bony tail and ten or even more limbs (two pairs pre-oral, three pairs post-oral), each attached to their own segment and with hands with two fingers. From this basic body plan all further morphologies were achieved through thagmosis, the fusion of segments. In almost all living onychognaths, the eye-segment fused together with the two pre-oral segments to form a solid cephalon, with the pre-oral legs becoming sensory antennae. Also, in almost all living forms, the first post-oral limb pair fused with the back of the skull to form mandible-like jaws, with the two fingers on each hand becoming arachnid-like cheliceres. In the majority of forms, the remaining six legs are used for walking, in a rather insect-like manner.

A good example of this is the diminutive Tynus, just 20 centimetres long, which can be best described as a cockroach-lizard. It is therefore also sometimes called the “Marsroach” (the alternative name combination “Cockars”, suggested by a particular member of the expedition has not won out, for obvious reasons). During the day it is mostly found underground to escape the desert heat, during the night it comes out to hunt smaller relatives and dust slugs. With its first pair of antennae it mostly smells, with its second pair it mostly hears. The breathing system of onychognaths is decoupled from the head, instead there are six breathing orifices, one in front of each leg, which lead to their own lung sack, somewhat similar to the booklungs of arachnids. In most onychognaths like the Tynus, the four sacks at the front specialize in oxygenic respiration, while the hindmost pair has a more elaborate structure to create better anoxic conditions for methanogenic respiration, hence the elongated section behind the hindlegs. Once morning arrives, the Tynus usually laps up dew from smooth surfaces or even licks it off its own eye with its tongue. The eyes of all onychognaths are solid lenses made of biosilicon. This has both advantages and disadvantages in the harsh Martian environment. On the one hand, with solid eyes, there is no need to shield them from dust and sand blowing with the wind, as there is no liquid surface which could clot up the particles. On the other hand, the recurrent abrasion by sandy winds does over time create scratches on the eyes, which can impair the vision of the animal if they start accumulating. Many onychognaths therefore have to shed their eyes and regrow them once they wear out. Usually, the eyes fall out asymmetrically timed, so the animal does not go completely blind during the regrowth phases.

Generally, two grades are distinguished within the phylum: the paraphyletic Archaeocephalia, which possess the ancestral chelicerous jaw apparatus and of which the Tynus is a part, and the monophyletic Cuneocephali, which likely derived from the former. In Cuneocephali, such as the Ifrit, the arm-bones holding the cheliceres have fused firmly to the cephalon and the bottom fingers have become an immobile lower jaw, also firmly fused to the rest of the skull. The sole moveable part are instead the upper fingers, which have fused into a singular beak which opens and closes sort of like a toilet seat. Why these bizarre “wedge-heads” evolved is hard to say, though the rigid design has in some species allowed for the attachment of surprisingly strong adductor-muscles for the upper jaw. Cuneocephali usually also have a more complex circulatory system than their forebearers. The individual lung sacks are interconnected, with the job of exhaling and inhaling being split up between the orifices and the oxygenic sections providing the methanogenic ones with carbon dioxide.

The Ifrit is a predator of smaller desert creatures like the Tynus. It usually kills them with well-placed, paralyzing bites to sections of the spine. Its actual method of eating is rather baroque, sometimes thrashing the carcass around or even performing deathrolls in order to rip out pieces of flesh. What is fascinating about the Ifrit is that it seems to be in an apparent phase of evolutionary transition. Cuneocephali descend from hexapods not unlike the Tynus. In the Ifrit however, the last pair of legs looks like it is in the process of vanishing, as they have shrunk and are dragged through the sand rather uselessly. But they are not completely vestigial, yet. Like all Martian animals, the Ifrit is hermaphroditic and once the time to mate comes, the two partners engage in rather daft wrestling fights to determine which loser gets to be impregnated. The small legs are used in these fights to help keep the opponent’s hindquarters down on the ground.

Common Hortax

The scaly, radially symmetric Hortax communis is one of the most common predators found in the shrublands and the desert edges. Having a diameter of about 60 cm on average, it is a member of the phylum Trichordata. Trichordates outwardly resemble starfish, though their internal skeleton, made of apatite and silicon dioxide, is made out of parts which structurally resemble more the bones of vertebrates. The name hails from the fact that each arm is supported by an arrangement which greatly resembles a spine, meaning that the skeleton of a trichordate looks like if someone stitched together three snake tails. At the bottom center of the body lies the mouth, which resembles a three-pronged beak. Opposing it on top of the body is a cloaca that also functions as a breathing orifice. Due to the mineral composition of the skeleton, some suspect that the Trichordata are most closely related to the bilaterally symmetrical Onychognatha, such as the Yrp the Hortax is hunting here, but embryological data does not support this. Trichordates do not develop from a bilateral embryo, but instead are radial from the get-go, meaning that their ancestor must have already been a radiate, perhaps more closely related to the Mollizoa.

Atypical for a radially symmetric creature, such as brainless starfish or jellyfish, the Hortax has a rather complex nervous system. The gut is ringed by a circular brain and each arm possesses a prominent ganglion and a primitive eye at its tip. Obvious ears or nostrils could however not be identified so far, though it is thought the hortax simply feels vibrations through the ground and smells through its mouth, like a snake. Observing a hortax simply being idle, it seems each arm has a bit of a mind of its own, not too dissimilar from the tentacles of an octopus. While one arm lies down, seemingly resting, another one might examine something on the ground or probe the sand, while the third stands high on lookout for danger or food. They seem to cyclically switch their shifts. Once direct action is required, however, the central nervous system seems to override any individuality and the three arms act in unison, slithering across the sands with disturbing agility and style.

Hortax hunt a variety of prey, such as spirifers, developing shellubim, onychognathans and smaller species of hortax. The prey is often grasped, sometimes even strangled, with the strong arms and then slowly killed through multiple bites with the beak. During feeding, some astronauts report hearing a purring sound coming from the Hortax, almost like a cat, but this has so far not been recorded.

Dust Slugs

One of the larger phyla on Mars are the Spiriferia (not to be confused with Spiriferida, a brachiopod order from Earth). These can be generally described as “armored slugs”, where the soft body is protected by a series of dorsal plates. Unlike molluscs, the muscular foot by which they move across the ground is segmented and split up into multiple pseudopods. The defining characteristic that gives this phylum its name is their unique mouth. While early researchers often compared it to the radula of molluscs, in reality it resembles more a larger version of the “corona” seen in rotifers. Two major classes can generally be identified in the Spiriferia, which have evolved two structurally different versions of such a corona. In the class Lobostomia, the corona is built into either a hood above or two large arms on the side of the mouth, which are beset with hundreds of hair-like setae. Through swishing-motions, these bristles transport particulate food to their mouths. In the class Verticutia, the corona is split up into a bristly “lower lip” and an “aggressive upper lip”, where the setae are replaced by teeth that are each moved in an alternating motion that can only be described as the biological equivalent to a scarifier (like the ones I used to work with in my father’s garden). One presumes that this originally evolved to effectively plough through nutritious ooze at the bottom of the sea (with the bristle-lip acting as a filter for food particles as in the Lobostomia), though in many derived forms it has become a tool for predation as well.

A polyphyletic sub-group of the Spiriferia are the so-called dust slugs, which is a general term applied to both lobostomian and verticutian spirifers which have, amazingly and independently, adapted towards lithotrophy, whereby Martian dust and sometimes even ground-up rock is digested with the help of lithotrophic areonts living in the animals’ guts. Almost all of Mars’ dust is made of iron oxides, which these microbes can turn into energy through iron reduction. The sifting also helps with taking up water in form of the dew laid down onto the sands in the morning. It should be stressed however that most of the iron-reducing reactions are inefficient, which is why dust is not the main diet of these organisms. Lobostomian dust slugs mainly sift the desert sands for smaller plants and for spores, aeroplankton and other organic debris that has sunk down, while the verticutian ones are mostly predators of smaller animals such as onychognathans and trichordates. Herbivorous verticutians also exist, which mainly shred up the water-bearing bases of desert-spongisporians. Another interesting trait which separates dust slugs from other spirifers is that their skin is not soft and wet, but instead dry and scaly, like in a reptile, allowing them to slide across the sands with the ease of a desert cobra. They also lay hard-shelled eggs.

Dustbowl Deserts

The hottest regions of Mars are also the driest for the most part, largely resembling the subtropical and steppe deserts of Earth. The flora and fauna here not only has to adapt to the typical trials of such regions, but also to Mars’ constant threat of extreme dust storms and dust devils.

In a stark contrast to Earth, most sand particles on Mars are small enough to be classified as dust, due to spending potentially a billion years being eroded in dry conditions by nothing but wind. Due to the low gravity, once the wind picks up such a dust particle, it can stay airborne for extraordinary amounts of time and impact the dunes again at an almost horizontal angle. One impact can cause multiple other dust particles to become airborne, which then also throw up more particles each, until the process cascades into a full-blown dust storm. And again, due to the low gravity, even light breezes can sometimes escalate into such storms, which can also last much longer than on Earth and travel great distances, as the arid air prevents the particles from clumping together. Dust storms most commonly occur during perihelion, when Mars receives 40% more solar energy than during aphelion. Although it is actually winter in the northern hemisphere during this time, the extra solar energy creates a highly dynamic atmospheric system across the Martian globe that translates into high winds in the northern lowland. These strong winds consequently animate the eternal sands to create dust storms, which can turn the entire lowland region into an almost literal dustbowl for multiple days, sometimes even weeks. The windspeeds reached during such events can go way over 160 km/h, which is in the range of category-2 hurricanes on Earth, a serious danger to our research facilities, though the force of the winds is weakened by the lower air pressure on Mars.

These dust storms also cool down the northern desert, making its winters harsher than they need to be. The storms form an almost protective envelope, where the dust particles intercept most of the solar energy. While this significantly cools down the surface, in turn it also heats up the upper atmosphere to burningly high temperatures. In some years, this process heats up the northern atmosphere so much that it actually becomes warmer than the summerly southern one and the dustbowls balance this out by flowing into the southern hemisphere, heating its air up as well. This consequently causes stronger winds than usual there, which kick up any unthawed dust over the tundra and eventually results in a global dust storm that can cover the whole planet for nearly two months. Such an event only comes to an end once the dust-envelope has created nearly uniform temperatures across the upper atmosphere of the whole planet, giving the winds no directions to flow towards. Thus they finally settle down and the dust with them. 

Another, common occurrence in the northern desert are dust devils, which can reach far larger sizes (sometimes many kilometres tall and hundreds of meters wide ) than on Earth and thus resemble tornadoes more, though their strong windspeeds of up to 100 km/h are again weakened by the lower air pressure.

Animal life can usually cope with these threats by migrating or burrowing underground to brumate out the danger. For the flora it becomes much more precarious, as photosynthesis is difficult when one’s whole body becomes covered in sun-blocking dust. Arephytes are nearly absent from these deserts, as they possess no adaptations to protect themselves from this threat. Spongisporia and Fractaria, on the other hand, have been able to develop unique pumping systems or wiping cilia with which to clean themselves. Most amazingly, some organisms, including some animals, have found ways to profit off the ever-present dust.

Image Sources:  

• Fig. 2: Insight Mission Images 
• Fig. 3: Jet Propulsion Laboratory