Tundras

The majority of the southern hemisphere of Mars consists of an almost continuous tundra. Life on the permafrost is hard, for in most places the temperatures rise above zero only for 134 sols of the year. In a few desolate areas this number can be well below 67 sols, while a few more fortunate ones have around 267 summer days, but in all of them the majority of the year is spent below freezing.

Apart from the red dust of the deserts, it is the tundra that gives Mars its red coloration. Polyfractarians are entirely absent from the flora, instead the most conspicuous organisms here are the red fronds, a type of monovexillan. As photosynthetic organisms they have likely evolved such a darkened coloration in order to better capture the faint light of a much farther away Sun. Red fronds have large, fleshy bases buried deep into the top-layer of the soil above the permafrost, which act as sugar storages for the long winters. The frond above ground is in a nearly desiccated and almost dead state during this time, with much of its interior water having been replaced by biologically produced anti-freeze. Photosynthesis halts almost completely during this time and the tundra becomes anoxic. Once the summer thaw comes, the top-layer of the permafrost melts and, because it can not drain away through the frozen underground, the water accumulates everywhere into bogs and ponds. The fronds seep up the water and spring back to life by digesting the anti-freeze proteins inside their body and producing their characteristic pigmentation. The whole tundra starts to bloom in bright red and photosynthesis resumes. These frond blooms occur on such a large scale that Earth-based telescopes have been able to observe them since the 20th century, giving humanity its first clue towards the existence of vegetation on Mars. The fronds use the short summers to produce as much sugar as possible for the next period of dormancy, as well as to produce spores. The majority of the fronds are asexual and their spores are carried by wind. These spores can stay dormant for a remarkable amount of time before germinating. Our scientists have been able to retrieve frond spores from a piece of permafrost that was at around 18’000 years old and when exposed in the lab to heat and light, they actually began to grow!

Fig. 2: Extent of tundraic climates. The small tundra-ring around the northern ice cap is not shown.

Sharing their environment with the fronds are various smaller spongisporians, which also stay dormant during winter. Though still capable of filtering the atmosphere for food particles, many of them have bumps and lichenous leaflets, in which photosynthetic endosymbionts live. The sporians profit from their production when the air is too empty, while the microorganisms profit from the protection during winter. These tundraic sporians reproduce much in the same way as the fronds.

Most fascinating is the scum-level growth of the tundra. Instead of grass, the most numerous organisms here are filulithophores, a type of filamentous macroareont, which carpets the whole biome. Like their pocupoan cousins, these are multicellular, though prokaryotic organisms that live through various forms of photosynthesis and possess tiny shells made of silicon dioxide. They are also red in coloration, though unlike in the fronds this is actually a structural colour achieved by the morphology of the shell. What purpose this serves is unknown. Filulithophores, like most macroareonts, are excellent nitrogen-fixers and are capable of enriching the tundraic soil with nitrogen amounts comparable to what is found in Earth’s tundras. Some hypotheses speculate that the low amount of nitrogen in the atmosphere of Mars might actually be their fault, though this is highly disputed. What is known is that many migratory animals from the equatorial regions get most of their nitrogen by feeding on the tundraic vegetation during summer. Unlike their mountainous cousins, filulithophores only grow a few centimetres tall, with most being in the millimetre range. They are the only organisms who seem to not go into a state of complete dormancy during winter, as most of their biomass is actually underground. Also present on exposed rocks, glacial erratics and naked soil are various species of flechtoids, similar to those found on the ice caps, but much more diverse and complex.

During winter, all animals larger than a few centimetres are completely absent from the tundra, having migrated towards the equatorial regions. The rest goes into deep hibernation underground. The sole exception is the yateveo, a species of wanderstalk with a bizarre survival strategy. Though largely sessile, it has almost completely given up photosynthesis and instead acts like a clam trying to be a carnivorous plant, by preying on particularly large wadjets during the summer migrations. It is a gamble, but when it pays off, it can feed off the trappings for the whole winter, thanks to its low metabolism.

 

Fig. 3: Observations of frond blooms from the 1960s.

In summer, things become much livelier. First come the herbivorous, power-flying variants of shellubim larvae, closely followed by the insect-like wadjets, which feed on the plankton and use the bogs formed by the meltwater to lay their aquatic eggs. These are then followed by larger flying animals, like vanators and the strange, hindwinged ballousaur onychognaths. On the ground also migrate various fusobranch onychognaths and bennus to feed on the frond blooms and sometimes to even rear their young in the tundra. Evidence, in the form of permafrost remains, exists that the tundra was once home to even larger animals. A few years ago, a quite sizeable, frost-mummified lower leg has been uncovered by an excavation team in deposits that are possibly around 100’000 years old. Beyond having been covered in characteristic feather-scales and belonging to some type of upright-walking cuneocephalian, not much can be said about the appearance of the leg’s owner, except that it was approximately the size of a reindeer or even a moose, much larger than anything currently alive on Mars. Soon after the discovery, some fringe theorists have claimed that a satellite image by the DIXON-4 Polar Orbiter actually shows a herd of these “Martian caribou” close to the southern ice cap still surviving until modern day, but all the low-resolution image truly shows is a couple of dark spots on an icy plain, which is much more readily explainable by flechtoid colonies or starbursts. The extraction of XGNA from the carcass has been unsuccessful, though as shown by the frond spores, younger permafrost remains might still be lucrative.

References:

• Fig. 3: Salisbury, Frank: Martian Biology. Accumulating evidence favors the theory of life on Mars, but we can expect surprises, in: Science, 136, 1962, p. 17 – 26.