Eios

Eios is the fourth planet from Tarsis-1.

Eios is the fourth and most habitable planet from Tarsis-1.

## In-Game Description

*“Eios is well known for being one of the most attractive destinations of the Tarsis-1 system. Although Eios has much smaller seas than most Kerbin-like worlds, the planet is believed to support complex life on its surface due to it meeting many of the requirements of a life-bearing world. However, Eios has also been shown to be rather inhospitable for Kerbin life due to a high concentration of toxic gases and large doses of radiation from Tarsis-1. Regardless, Eios is the prime destination for colonization in the Tarsis-1 system.”*

## Discovery

Eios was discovered via the Radial Velocity method at the same time as many of the other Tarsis planets. Eventually, radio signals were sent out to the planet, though none were responded to. This led to many Kerbals taking an obsession to the mysterious world, which only grew when pictures of the planet revealed it to be an Eyeball Planet, which the Kerbals likened to their own eyeballs.

When the scientists on Kerbin studied Eios’ atmosphere, they determined that the atmosphere has toxic amounts of Hydrogen Sulfide. This quickly disappointed much of the scientific community, and even the calm and collected Linus Kerman allegedly threw a clipboard against the wall. Wernher Von Kerman eventually discussed the possibility of chemosynthesis being the way life on Eios survived, which was later confirmed by sulfur being detected in the atmosphere, leading Kerbal scientists to frantically conduct more research and prepare missions to the planet.

Wernher Von Kerman himself stated, “Getting to Eios is a top priority for the Kerbal Space Program.” He reportedly added under his breath, “There’s something fishy with that weird eyeball world.”

And fishy it was. The planet’s oceans were reportedly filled with a sea-dwelling invertebrate species called Eiosian Jellies. Additionally, two plant species were also found, called Bradley Structures and Amphidorasus. After scans of the planet were taken, a fossil record was determined and a planetary history was compiled.

Eios likely formed about 4 billion years ago, at the outer edge of Tarsis-1’s habitable zone. About a billion years later, the planet cooled and Eios was likely a water planet with an orbital period that was different from its rotation period. Over the course of a few hundred million years, Eios began to develop microscopic single cell organisms. There were millions of microorganism species, though one species eventually became the dominant species on the planet. These organisms eventually came to be known as Bradley Structures. Bradley Structures use a process called chemosynthesis to synthesize energy-rich molecules from the abundance of hydrogen sulfide in the water.

Around 1.5 billion years ago, Eios’s orbit decayed slightly, and this led to the planet being tidally locked, and the water on the day side of the planet to evaporate. Consequently, the Bradley Structures started to grow, seeking a deeper water table. On the other side of the planet, Bradley Structures also grew, due to the ice freezing and them needing to also seek a deeper water table. Eventually, the vast majority of the water on the day side evaporated. The Bradley Structures retained the ability to use chemosynthesis to form energy-rich molecules from hydrogen sulfide in the atmosphere to survive. At the same time, as the water on the night side froze, the Bradley Structures evolved the same way.

600 million years ago, the first fossils of more primitive Eiosian Jellies were observed. Their undulating fins had not properly developed yet, leading to Kerbal scientists determining that these fossils are a more primitive version of the modern Jellies.

Around 500 million years ago, a parasitic plant called Amphidorasus started appearing. The plant would spread single cell spores to small Eiosian Jellies, where they would eventually kill them and mature into adult plants.

Currently, there are only three living species on Eios. Those being Bradley Structures, Amphidorasus, and Eiosian Jellies.

## Physical Characteristics

Eios is classified by Kerbal scientists as an Eyeball Planet, which is a type of tidally locked world that’s spatial features make it bare similarities to eyeballs. These types of planets tend to either be very warm or very cold, which leads Eios to be a unique example, since it is in the habitable zone of its star. Eios has many biomes, each with their own unique areas to investigate.

Oceans

Eios’ oceans are a popular destination on Eios, and they cover approximately 35% of the planet’s day side surface. They mostly appear as a border between the ice sheet and the other land.

Habitable Areas

The habitable lowlands are some of the only areas on the planet that have the capability to support life. These areas are almost always close to sea level. Additionally, the non-habitable lowlands might be less habitable, but their potential for colonization is nearly as high as the habitable lowlands.

Eios also has midlands that are present all over the day side of the planet. These areas are also prime for colonization, with many sections being flat. The elevated sea level does increase the risk for radiation exposure, but the risks are not high enough to affect readings significantly.

Radioactive Areas

The highlands of Eios face the highest consistent amount of radiation on the planet, due to them usually being the highest mountain peaks. A barren wasteland, this mountainous area is not to be colonized without taking proper safety precautions. Additionally, the Substellar Desert is the part of Eios that faces the most radiation, since it’s the part of the planet that faces Tarsis-1 directly. Life in this biome is sparse due to the radiation, and it receives more radiation than any other area on the planet. One of the original kerbals to study Eios says, “[Being on Eios is] the equivalent of living near a small nuclear meltdown.” Exploration of this biome is ill-advised without high grade radiation protection suits.

Studies show that the genomes of the species on Eios have redundancies to protect against mutation from radiation. Further study is recommended.

Ice Sheet

Eios’ ice sheet covers approximately 60% of the planet’s total surface area, and composes the vast majority of the night side of the planet. This ice has similar properties to perma-frost, and likely froze about 1.5 billion years ago.

## Atmosphere and Climate

Eios’ atmosphere is layered, similar to Kerbin’s. The atmosphere is mostly composed of Nitrogen and Oxygen. Hydrogen Sulfide also composes about 1% of the atmosphere, which the floral species on the planet use for energy. As a byproduct of hydrogen sulfide chemosynthesis, sulfur is generated, which is also detected in very small amounts in the atmosphere.

Water vapor is also detected in Eios’ atmosphere, suggesting a water cycle, though this is extremely uncommon for a Tidally Locked planet. Atmospheric scans have not come up with any proper solutions as to why the planet has clouds consistent with non-Tidally Locked worlds, and more research into the atmosphere needs to be done in order to get an answer.

## Possibilities of Life

Eios is known for its strange and exotic flora and fauna species.

Bradley Structures are the largest plant species on the planet, reaching over 70 meters tall. While these organisms were originally thought to be rock formations, further studies show that the colossal structures are actually single cell organisms that use chemosynthesis to form energy-rich molecules from hydrogen sulfide in the atmosphere to survive. Bradley Structures has 5 podia-like appendages with secondary branches. There are three major theories amongst Kerbal scientists as to why these appendages are observed. One theory is that they are used for nutrient acquisition, similar to roots of trees that are observed on other planets. The second theory is that these appendages are “tethers” that keep the bulbous part of the organism from interacting with the ground and being destroyed. The third theory, and the one with the most evidence, is that the Structures use the appendages for balance, similar to some organisms found elsewhere.

The exact age of the Bradley Structures is unknown, and theories suggest that the ones observed on the planet are the last of their species.

The Eiosian Jelly is the only non-flora species observed on Eios. They are fairly primitive creatures, by Kerbal standards. They are cannibalistic organisms and they’re able to sense prey, which consists of other members of their species at all developmental stages. The ability to sense prey also suggests behavioral responses, which was first observed when a kerbal standing at the edge of a shore noticed one of these organisms seeming to curiously look back at him. Physically, an adult Eiosian Jelly is around 6 inches (15 cm) in length and about 1.5 inches (4 cm) in width. They use 2 undulating fins on both sides of their body to propel themselves through water, similar to some species of invertebrates observed on Kerbin. To eat their prey, they have a Buccal cavity that is controlled entirely by muscle. Due to their status as invertebrates, they don’t have any ossified structures in their bodies, further indicating a primitive nature.

The second plant species is called Amphidorasus (meaning a spear that can live in both water and land). Amphidorasus also starts as a single cell organism, though it quickly evolves into a multicellular organism, similar to Dictyostelium found on Kerbin. It also uses chemosynthesis for synthesis of energy-rich molecules, similar to Bradley Structures. The adult version of Amphidorasus looks similar to spears, and each one is between 7 and 10 meters tall, while the development stages of Amphidorasus are all mostly microorganic or are small in size.

The life cycle of Amphidorasus is that of a fungal parasite, though it cannot be classified as such. Amphidorasus starts off as a single cell spore that enters an Eiosian Jelly through ingestion during meals, as they’re either sensed as eggs or accidental. Amphidorasus spores survive digestion due to the quiescent nature of the spores and their hard cell wall. Over years, as eggs or other prey are digested, a nutrient environment is made available that activates the spores to begin their development as Amphidorasus motes. The motes continue to gestate and evolve into a multicellular organism, and eventually the motes kill the Eiosian Jelly. When the Eiosian Jelly eventually washes up on shore, they go through an event called the emergence, where the motes depart the Eiosian Jelly and enter a phase called the “Slime Mold Phase.” This phase lasts for between months and years, and consists of them moving themselves vast distances across the planet. Eventually, Amphidorasus will stop moving and will start growing vertically, with spores being formed near the top of the spear-like structure. Over time, the spores get carried by the wind and some of them land in the water, where they are consumed by Eiosian Jellies. The cycle then starts again.

The lack of diverse life on this planet has baffled Kerbal scientists, and further explanation may give answers to the question.

## Biomes

* Poles
* Water
* Habitable Lowlands
* Lowlands
* Midlands
* Highlands
* Substellar Desert
* Ice Sheet