Earth

Earth is a rocky planet with naturally occurring life. It has a notably large moon for its size which probably formed in a very unusual way. It is home to three groups of notable lifeforms; Earth plants, green plants, arthropods, invertebrates with an exoskeleton, and tetrapods, animals with an internal skeleton and four limbs. From the tetrapod lineage has come a sapient species known as humans. Earth is legally owned by the Martian Union, but the societies inhabiting Earth today govern themselves. Both the MU and Earth’s peoples collaborate to keep the planet as a protected region for the sake of its native lifeforms.

Planetary environment

Earth is a mid-sized rocky planet, at a diameter of almost 13,000 kilometres. It has a day length of 24 hours, and has an axial tilt that produces seasons. It has one moon, Mun, which is unusually huge for a planet that size- about a quarter of its parent planet’s width. While most other moons are planets or asteroids captured by the gravity of their parent planet, Mun is thought to have formed as a result of another small planet colliding with Earth.

Earth’s climate is rather cold, as it is currently in the interglacial period of an ice age. However, it has recently been rapidly warming and cooling very intermittently- first as it left a glacial period thousands of years ago, then as human activity dramatically warmed it further, and finally as recent geoengineering efforts have cooled it back down to a more acceptable temperature.

Though Earth was once practically covered in cities and farmland, they are being swiftly reclaimed by nature. Deserts are shrinking, and once-extinct rainforests are slowly reappearing. It will take more than only hundreds of years for the climate to change back to what it once was, but the process is beginning all the same.

Life

Like most planets bearing complex life, the base of the food chain on Earth consists of photosynthetic organisms known as plants. Earth plants are green to match their yellow star. They have many adaptations common to plants, like trunks, seeds, flowers, and fruit. However, they are not as derived as some known plants.

The other major macroscopic group of life on Earth are animals. Earth has many groups of animals common to life-bearing planets, like sponges, jellies, slugs, and worms. It is also home to a myriad of diverse arthropod groups, like insects, arachnids, and crustaceans. The largest animals on Earth are vertebrates. Unique to Earth and Pennacerti are the tetrapods, a clade of four-legged, two-eyed, jawed animals. Tetrapod groups include amphibians, reptiles, and mammals.

The history of life on Earth is a fight for dominance between groups. For much of the history of complex life, arthropods and fish reigned. Tetrapods started becoming more prominent at the end of the Carboniferous, about 300 million years ago. A clade of giant reptiles known as dinosaurs rose to dominance during the late Triassic, 200 million years ago, before going mostly extinct at the end of the Cretaceous, 65 million years ago. Since then, mammals have ruled. In the last thousand years, many large mammal species have gone extinct due to human activity, but conservation efforts like the Lunar Extinction-Reversion Project make a permanent change in the biosphere unlikely.

(Pictured: an example of an Earth tetrapod; an extinct, semi-aquatic reptile known as elasmodraken. Discovered in the 22nd century, elasmodraken is a popular prehistoric animal due to how much of it’s soft tissue- even down to the colour- has been preserved.)

Native sapient inhabitants

Earth is home to one sapient species; humans. The biology of humans is detailed here.

Since the industrial revolution began in the 18th century, humans have had a devastating impact on Earth’s ecosystems in the forms of pollution and climate change. At the same time, they have developed technology like electricity, computers, and rockets, which would eventually allow them to travel to space.

By the time humans had set foot on their moon and sent non-sentient robots to nearby planets, the possible deadly impacts of climate change and pollution were known about and feared. However, the people who could do something about it didn’t seem to care. In the late 21st century, small colonies on Mars were established, and people hoped they could escape the climate crisis by going to space. By the time it was established that life in space for most people was hundreds of years away, it was too late to prevent the destruction that had already happened. Deserts expanded, rainforests shrunk, and the only thing left of hundreds of species were refrigerated DNA samples.

For a hundred years, a world in crisis worked to prevent more damage from being done. As clean energy solutions were established all over the world, a fragile political climate combined with unregulated new technology to produce atrocities. Finally, in the tail end of a dark century, humans would make first contact.

Many humans would immediately move to the aliens’ planet, Gi. It’s ecosystems were equally ravaged, but at least it wasn’t in a climate crisis. Humans and Azi lana agreed that something needed to be done, and the terraforming of Mars to create a paradise for humans was proposed. It was an ambitious idea, but the newly-established UHALE decided to take on the challenge.

By the end of the 24th century, Mars’ terraforming was completed, and people moved there in droves. Massive migration and a baby boom caused Mars to accumulate five billion inhabitants in just over 200 years- something that was previously unprecedented. At this point, Mars declared independence from the UHALE, and became the Martian Union. The only people left on Earth now were those who couldn’t afford to move or those who valued living on the planet more than they valued living a comfortable life. However, this was about to change.

In the several hundred years since clean energy became the norm, Earth’s ecosystems had slowly begun to recover. The UHALE, Martian Union, and several other nations agreed to instate an ambitious plan to entirely restore them- by turning the entire planet into a national park.

Many steps taken toward this goal were entirely controversial. The MU essentially strong-armed the other nations involved in the project into giving it full control of Earth, by holding its resources over their head. A large number of people still on Earth were only there because they couldn’t afford to move elsewhere, and when they were essentially forcefully moved, only a few nations offered to take them in for free, so many were left homeless.

At first, there was a hot debate over whether those who wanted to stay should be forcefully moved, too. Eventually the project managers reluctantly agreed to let people stay for religious or cultural reasons, like many Native American, Australian, and Pacific Islander peoples. Many question if the plan was worth it at all, or if the same result could have been achieved by restoring Earth’s ecosystems without displacing many people.

Regardless, the Earth is doing better. The Lunar Extinction-Reversion Project has been set up by the MU to help restore once-dead ecosystems. The LERP does things like use geoengineering to cool the planet back down to pre-industrial levels, use cloning technology to bring back extinct species like tigers and elephants, and use various methods to control the populations of invasive species.

The remaining peoples of Earth, many of whom have always been concerned with the upkeep of Earth’s ecosystems, often collaborate with the LERP project to do what they can for the planet, too. Humans and Earth have a long and storied history, but the hope is that one day Earth’s environment can be fully restored, and that the people of Earth can sustainably live among it once again.