Rhinoceros Warhoon

Archaeocephalians come in many forms, one of the most distinctive perhaps being the rhinoceros warhoon (Rambisaurus stamperi). Why it has that common name is obvious. The front part of the cephalon, the rhinotecum, is not just radically elongated, but also curves upward to form a sort of horn. What exactly this horn is used for is unfortunately not entirely known, despite extensive observation of this species. Kirkhope’s most extensive study so far has concluded that the horn serves a solely visual function, being basically a flagpost that the warhoon uses to flap and flutter its antennae from, either as a warning or mating display. Some accounts do, however, mention warhoons using their horns for interspecific pushing-matches, very much like stag beetles on Earth, which is sometimes stated as a fact in pop-science books. But these accounts are purely anecdotal and this behaviour has yet to be confirmed in a scientific context.

Rhinoceros warhoons mainly inhabit the dry slopes and shrublands surrounding the western Tharsis plateau. They are quite hardy organisms adapted for tough times. A large part of their gut is dedicated towards storing water, much like a camel, and their thick hide and osteoderms are excellent at preventing evaporation. They are extreme omnivores, their robust cheliceres allowing them to bite through the hard skin of succulent flora, as well as splitting the bones of any animals smaller than them. On occasion they have been observed lapping up bone-marrow with their tongue or even grinding up certain minerals. Their skin is also thick enough to allow them to feed on the predatory red weeds without being stung by their syringe-like urticating hairs.

Characteristic for the warhoons is a dorsal armour composed of multiple osteoderms, which may serve multiple functions. It obviously provides protection from certain mountain predators, such as smaller ballousaurs, but may also serve as a mineral storage or anchorage for certain muscles. Interestingly, the osteoderms are strongly infused with silicon dioxide. This has been interpreted as a form of protection against UV radiation, which poses a bigger danger on Mars than on Earth, especially at the high elevations that the warhoon lives on, as the lower amounts of oxygen on the planet also mean a weaker ozone layer. Silicon dioxide, in other words glass, is very good at blocking at least UVB rays.

On the topic of siliceous bodyparts, warhoons exhibit multiocully, meaning they have more than one pair of eyes. This is exhibited by multiple different onychognath groups, which could mean that it either was beneficial enough to convergently evolve or may actually be the ancestral trait. The benefit is obvious, as onychognath eyes are solid and are asymmetrically shed and regrown to get rid of scratches. The more eyes one has, the less the vision is impaired during these replacements.

Compared to other Martian animals, relatively much is known about the reproduction of the rhinoceros warhoon, thanks to Kirkhope’s work. The mating individuals determine impregnation through antennae-displays and head-nodding, upon which internal fertilization follows. Warhoons are viviparous and develop multiple uterine eggs, but usually only one or two of these eggs fully develops, nourishing itself on the yolk of the surrounding eggs once it has used up its own. Pregnancy can last up to one or two Martian years, depending on the altitude and availability of food, the warhoon being able to pause the development of its embryos if conditions are inconvenient. Once born, the young are fully developed and capable of living on their own.

Rhinoceros warhoons are often noted for their resemblance to the Antennarhynchi, a group of archaeocephalian tagmasaurs from the Cydonian period, to which the famous Tapinotherium and the Glyptosauria belonged. These likewise possessed an upturned rhinotecum and extensive body-armour, though they walked on erect legs instead of splayed ones and were the size of military vehicles. But this resemblance seems to be entirely convergent, as the finer skeletal anatomy of Rambisaurus shows that it is closely related to modern, lizardine onychognaths like the tynus (Sivgin 2345). Nonetheless, studying the function of the warhoon’s horn may allow insight into how these extinct aliens may have used theirs, as similarity in form likely implies similarity in function.

References:

• Kirkhope, David: Life cycle and Ecology of the Rhinoceros Warhoon, in: Areobiology, 195, 2294, p. 94 – 108.
• Sivgin, T.K.: Life on a Dead Planet. The first 3 billion years of Evolution on Mars, Zürich 2345.

Volcanic Slopes and Plains

An ancient voice grumbles through the air and the ground. A tall tower rules above the desert. Its fiery breath melts its snow-capped peak. The waters dribble down the talus to end up in a pathetic but vital stream. A meagre gift by the underworld gods to the inhabitants of these harsh sands.

One of the bigger surprises our geologists faced on Mars was that many of the volcanoes are very much still active. The surprisingly frequent eruptions might very well be what still keeps this planet alive, as without their gases much of the atmosphere might already have been carried away by the unrelenting solar rays. Volcanoes form such an important part of the Mars system because the planet has long ago lost any semblance of plate tectonics. On Earth, the mechanic movements of the plates are the main function by which the molten interior of the planet gives off its heat and energy. On Mars, volcanoes have instead become the main outlet, often growing to titanic sizes, as the massive amounts of magma fizzle out for millions of years in the same spot with no tectonic plate moving over their hot spot. Imagine all the islands of Hawaii being stacked on top of each other instead of standing in a line. This is how you get something like Olympus Mons, the tallest mountain in the entire solar system, which is not only nearly 22 km tall, but also has a surface area the size of Poland.

The vast majority of Martian volcanoes are such Hawaiian-type shield volcanoes, though they still differ in many ways from the shield volcanoes on Earth. The low gravity causes a greater accumulation of gas bubbles in the upwelling lava, which means that Martian shield volcanoes can erupt explosively, with massive clouds of ash and even pyroclastic flows, something more typical of Plinian eruptions on Earth. Due to the gravity, the magma also becomes less buoyant, meaning that the magma chambers feeding the volcanoes lie much deeper underground and are much bigger. Due to the depth, this means only the biggest of the big magma chambers actually reach the surface to cause eruptions. Mars therefore has a lower rate of eruptions than Earth, but when an eruption does happen it usually results in a titanic catastrophe with much wider and longer-lived lava flows on the surface. Such events have thankfully not happened yet during our stay, but several mountains, especially Elysium Mons, are under close observation.

The two major volcanic provinces on Mars are the Tharsis Plateau and Elysium Planitia. Tharsis consists of the aforementioned Olympus Mons, Alba Mons to its north-east and a chain of three shield volcanoes, Tharsis Montes, to its south-east, all arranged in a suspiciously straight line and consisting of Ascraeus Mons, Pavonis Mons and Arsia Mons. Between these five mountains exist various series of smaller volcanic cones, formerly called either tholi or paterae. Today it is recognized that these are not a separate type of volcano, as formerly believed, but that tholi and paterae are instead simply the top cones of much older shield volcanoes, whose bases have been buried by billions of years of lava flows. Life on much of Tharsis is harsh if not downright impossible. The height makes the air extraordinarily thin and the temperatures predictably low. Nearly the whole region is below the 0°-isotherm and almost all the area of Olympus, Alba and the Tharsis Montes is covered in large ice sheaths that are connected to the major glaciers of the South Pole. Only the most extremophilic microbes can cling to these environments. Conditions become only marginally better in the lower plateau between Alba Mons and the Tharsis Montes, where temperatures rise above freezing for only 67 sols (out of 668 per year). On the eastern slopes of Alba Mons leading down into the northern lowlands, conditions become dramatically better, with 268 sols spent above melting point. In those faint summers, the permafrost thaws and the rims of the glaciers above start to melt. The mountain valleys thus become inundated in stagnant bogs and ponds and the flora springs back to life from its deep winter sleep. The bogs are often anoxic, while the melting permafrost releases sulphuric molecules from the volcanic soil, making this environment ideal for anaerobic life. Primitive arephytes are predictably abundant in these Martian Alps.

The other major volcanic province, Elysium Planitia, lies at the edge of the eastern hemisphere and consists of Elysium Mons, Albor Tholus and Hecates Mons. Together they form a somewhat circular feature which stands out of the otherwise flat northern hemisphere like an island. Elysium is not as tall as Tharsis and is not wholly covered by an ice sheath. Conditions are thus generally more hospitable, but still precarious. Our geologists suggest that only a few tens of thousands of years ago an eruption had occurred on the west of Elysium Planitia that may have devastated an area the size of the United Kingdom. An explosive eruption first seems to have thawed all the permafrost of the mountain’s peak, leading to a catastrophic flash flood, followed by pyroclastic flows, streams of lava and massive ash fall. Time will tell if such an event might occur again in our lifetimes.

Apart from these two regions, there are smaller, solitary volcanoes, some active, some dormant, spread all throughout Mars. Hadriacus Mons near the Hellas Basin is one example, as is Eden Patera in Arabia Terra.