Athyrmagaia, Earth's Lost Brother

Our first destination in our exploration of life throughout Doppleganger (and our titular main focus throughout this project) will be the most spectacular and beautiful world of all; Athyrmagaia. Even back in the 29th century, when this planet was first discovered, finding planets with life on them was no longer that much of a surprise. Though they are indeed quite rare, our invention of the Alcubierre drive has made them much easier to find, reducing what could be thousands of years of space travel to just mere minutes or hours. This, paired with the comprehensive galactic mapping provided by the Fraternity, also aided in the process. Indeed, thanks to this technology, we now know of over 200 different worlds with life within the Milky way.

What makes Athyrmagaia truly special, however, is that it is one of the most Earth-like planets ever discovered, to the point that our researchers have even referred to it as "Earth's Lost Brother". This shouldn't be that much of a surprise, considering that the rest of the Doppleganger system appears like a crude replica of our own Sol, but it is nonetheless a very remarkable discovery. Not only does it have the same atmospheric composition (nitrogen, oxygen, argon and carbon dioxide), but it also has roughly the same mass, diameter, density and gravitational pull. It also has a carbon-based DNA/RNA biosphere, with microbes,  fantastical-looking "plants", "animals", and a variety of transitional life forms. By finding this planet, we have also found new friends and allies in it's native people, the Astutocentaurus, further adding to our list of interstellar comrades in the Fraternity.

The planet isn't without it's alien "quirks", however. The name we gave this planet is of Greek origin, and when translated to English, it means "Toyland". Indeed, many of the forms of life that live here look like they'd be at home in a child's toy chest. Others, however, might look like they came from your spouse's drawer. The "spiders" look like dolls, the "snails" look like toy trains and cars, and a seemingly endless amount of other life forms look like something best left unsaid. The native "plants" have cuticles made of a glossy bioplastic, and have clonal stems akin to stacked LEGOs. The dominant endoskeletal organisms are actually modular descendants of arthropod-like organisms, and they are capable of disassembling and reassembling their bodies at will. The Astutocentaurus can do this as well, and boy oh boy do they make the friggin' most of it. The organisms that could be considered "vertebrates" are evolved from radially symmetrical ancestors and some of the forms that live down under look like something out of Harald Stumpke's nightmares. 

Today it is the 40th century, and the entire sum of knowledge regarding this remarkable planet is the culmination of over 200 years of research. Even today, we are still learning more about this planet's biosphere, it's past, the origins of life, and the cultures of the many different native peoples that call it home. With the help of friends both on and off world, our knowledge of this world will continue to grow.

What the heck is Athyrmagaia?

Comparison between Earth and Athyrmagaia.

Athyrmagaia is the third planet of Doppelganger, and it lies right in the system's Goldilocks zone. It is one of three celestial bodies in this system that currently harbors complex multicellular life, the other two being the sweltering hot Musp and the frigid Hel, both of which we will examine at a later date. Athyrmagaia is about 93.928 miles away from it's home star, and it travels an elliptical counter-clockwise orbit that is about 413 Earth days long. It's axial tilt is about 24.2 degrees, which results in slightly more dramatic seasons throughout the year. With an axial rotation speed of about 893 mph, its days are about 28 hours long, just four more hours longer than our own planet.

Athyrmagaia has two natural satellites, nicknamed "Nicholas" and "Kringle" respectively. Nicholas behaves fairly similarly to the Terran moon, and it's counter-clockwise orbit takes about 29.5 local days to complete. It's most fundamental difference, however, is that it has its own sub-moon, Kringle, which is less than a quarter of its size. As Nicholas orbits Athyrmagaia, Kringle occasionally comes between them, which amplifies lunar gravitational forces. As a result, the tidal patterns on Athyrmagaia are much more complex, and in addition to the daily cycle of high and low tides, there is a larger monthly cycle in which the tides get their highest and lowest at the very middle of the month. The moons are tidally locked, with Nicholas being locked to Athyrmagaia and Kringle being locked to Nicholas.

Geophysical Characteristics

 

A crudely illustrated map of the natural world, based on maps from Amsa-de-Luvia's library.

Several of Athyrmagaia's geophysical characteristics are shockingly close to those to those of Earth. It is about 12,742 kilometers in diameter and has a total mass of 5.972 × 10^24 kg, and the centrifugal forces of its axial rotation give it a subtly ellipsoidal shape (although it's practically imperceptible). Its chemical composition is also rather similar; the crust is made up of oxides containing elements such as aluminum, calcium, silicon, iron, potassium and magnesium, and its mantle is a mixture of superheated rock and magma comprised of silicates. It's core, just like that of Earth, is a 1,200 kilometer sphere of superheated iron and nickel. It is a much older planet, however, estimated to be about 8.043 billion years old. Despite its advanced age compared to our home, Athyrmagaia is still a very tectonically active world. Mid-ocean ridges constantly ooze hot magma as tectonic plates slowly and steadily shift the Athyrmagaia's surface features, and active volcanoes can be found here as well. Its metallic core also acts like an electrical generator, and the kinetic energy it produces generates a strong magnetosphere that shields the planet's surface from deadly UV radiation. It should be noted, however, that there is some geological evidence that Athyrmagaia experienced an unexplained, albeit brief, period of "tectonic arrest" around 230 million years ago. This event is believed to be linked to the Borea-Comedian Mass Extinction Event, and was likely responsible for the formation of Cronos, a monstrous (and thankfully long dead) shield volcano with a surface area comparable to Saudi Arabia.

Just like Earth, a majority of Athyrmagaia's surface is comprised of an interconnected global ocean with large continental landmasses. Compared to the more generously distributed Earth, however, Athyrmagaia's continents and oceans are much more localized, with the northern latitudes being mostly land and the southern latitudes being mostly ocean. The ocean can be further divided into the Great Central Ocean, the Polar Ocean, the East and West Crescent Oceans, and the Comedian Ocean. Inversely, the planet only has three continents, that being Borea, Comedia, and Austrus. Although the continents are few, they manage to make up a fairly substantial portion of the planet's surface. Borea, the biggest continent, exceeds both Europe and Asia in size, and is itself formed from two smaller continental units (Macroborea and Microborea). It is so large that it wraps around almost the entirety of the northernmost latitudes, and the mountain range that forms the border of its larger and smaller regions runs straight through the north pole. It's western neighbor, Comedia, while smaller, still exceeds most of Earth's other continents in terms of scale, including Africa. On the opposite end of this scale is Athyrmagaia's only southern hemisphere continent, Austrus. It is the smallest continent of all, so much so that it has less surface area than our own Australia. The rest of the southern hemisphere, save for the southernmost portion of Comedia and a few islands, is almost entirely marine, and the south pole is essentially in the middle of the ocean.

Atmosphere, Hydrosphere, Biosphere and Carbon Cycle

Athyrmagaia has both producers and consumers. This particular consumer is of the "kill you while your back is turned" variety.

Athyrmagaia's atmosphere is nearly identical to Earth's. In terms of composition, it is about 78% nitrogen, 21% oxygen, and 0.9% argon, while the other 0.1% is comprised of other gases such as carbon dioxide and neon. It also lacks a definite boundary, and at sea level it has an average atmospheric pressure of 1013.25 millibars. This means that not only is it breathable for us Humans, but it means that the surface can be explored without the aid of a pressure suit. Similar gases are found in the oceans as well, though as expected they are present in different quantities.

An Earth-like atmosphere and hydrosphere also means an Earth-like biosphere. With the exception of a small number of Archaean-like methanogens, a vast majority of the microbial and multicellular organisms on Athyrmagaia are aerobic respirators that use oxidative phosphorylation to produce ATP, and require essential elements such as oxygen, hydrogen, nitrogen and carbon to survive. Not only do they rely on this Terran atmosphere to live and breathe, but they also play a role in the recycling and replenishing of its gases. The heterotrophs ("consumers") feed on other living things as they use oxygen from the atmosphere to power their metabolism, releasing carbon-dioxide as a byproduct. Meanwhile, the autotrophs ("producers") replenish this oxygen by using carbon dioxide and abiotic energy sources to produce their own food, which separates the oxygen from the carbon and reintroduces it to the atmosphere. It was also these autotrophic forms that made the planet's water and air breathable to begin with; back before the first autotrophs and heterotrophs evolved, oxygen content was much lower, and there was significantly larger quantities of carbon dioxide on both land and sea.

Biochemical and metabolic similarities aside, it is still quite an alien biosphere compared to our own, and there are multiple discrepancies between Earth and Athyrmagaia biology that complicate the possibilities of human habitation. As we have mentioned many paragraphs ago, the "plant" life uses polylactic acid in addition to cellulose to construct their cuticles. This substance is indigestible to Earth animals, but many of the native organisms are well suited for dealing with it. The planet's equivalent of cellulolytic "bacteria" can break down polylactic acid using the enzyme proteinase K, which degrades the substance through hydrolysis. Some herbivorous animals are also able to produce this enzyme to assist in digesting vegetation, though most just utilize symbiotic forms of the former microbes to do so. It also just so happens that polylactic acid is highly flammable, and it releases gaseous isopropyl alcohol when it is burned with flame. Due to this, naturally occurring wildfires often release plumes of toxic gas that linger for several days before dissipating. Fortunately, most of the native fauna are highly resistant to these toxic emissions.

Climate, Weather and Biomes

Athyrmagaia's biome map.

Athyrmagaia's global climate is one that us Terrans would be very comfortable in. It's global temperature is similar to that of Earth during the Pliocene epoch, and it is currently in the midst of a minor warm period that started about 2,000 Terran years ago. Unlike the artificially-induced global warming that once threatened our Earth, Athyrmagaia's warm period is a wholly natural climatic trend, and it is a result of the millennia-spanning variations in its proximity to its home star. Based on current estimates, the planet will likely enter another glacial maximum (or "Ice Age") within the next millennia, as the planet has already started cooling down slightly over the course of the past century of study.

A model illustrating global atmospheric circulation on Earth. This model is applicable to Athyrmagaia as well.

Just like Earth, Athyrmagaia's surface can be subdivided into latitudinal belts that constitute regions of relatively homogeneous climate. From the equator to the poles, these bands represent tropical, subtropical, temperate and polar climates respectively. This is because latitudes closer to the poles tend to get less direct sunlight than those in the tropics. Some of the other major determining factors of regional climate and weather on Athyrmagaia are atmospheric and oceanic circulation; Tropical and polar easterlies in higher and lower latitudes blow from the east, while prevailing westerlies in middle latitudes blow from the west, which distributes both warm and cool air across the land and sea. Oceanic currents also play a part in this process, bringing precipitation from the tropics to higher and lower latitudes. These phenomena, combined with the varied topographical features of landmasses, forms a wide variety of biomes. The poles are capped with ice and tundra, while the equator forms a belt of steamy jungle. Subtropical latitudes form dry forests, shrublands, deserts and savannahs, and the temperate latitudes consist of forests, steppes, and taiga.

As a result of its 24.2-degree axial tilt, Athyrmagaia is also a highly seasonal world, with springs, summers, autumns and winters that become more noticeable as you travel further away from the equator. The seasons of the north and southern hemispheres are opposite to each other; In the northern hemisphere, the year starts with winter, which is followed by spring, summer and autumn until it cycles back to winter at the end of the year. In the southern hemisphere, the year instead starts with summer, which is followed by autumn, winter, and spring and then ends with summer once again. At the equator, however, no such seasons exist, with there instead being two wet seasons and two dry seasons. Larger climatic trends have also occurred as a result of variations in the axial tilt and proximity to the sun over the course of millions of years, such as the current warm period.