Solar System

Sol and all 8 planets with scaled sizes (distances not to scale)

**Location:** Milky Way Galaxy/Local Cavity

Solar System is a system of objects bound to the star Sol and orbit it. The system has eight planets, seven dwarf planets, and other smaller bodies such as asteroids that orbit Sol directly and more than 100 moons that orbit Sol indirectly. Solar System is unique in charted systems of the Milky Way Galaxy, as it is the one of the only three star systems to have more than one body with an active biosphere, with the other two being the Relic System and 61 Ursae Majoris System.

The Solar System was formed around 4.6 billion years ago from the collapse of a giant interstellar molecular cloud. The vast majority of the system's mass lies within Sol, The four smaller inner planets, Mercury, Venus, Earth and Mars, are terrestrial planets. The next two are also the system's largest planets. Jupiter and Saturn both being gas giants, and being composed mainly of hydrogen and helium; the two next planets, Uranus and Neptune, are ice giants. There are five dwarf planet in the system with the Pluto being the largest. seven of the planets and six of the dwarf planets are orbited by natural satellites, usually termed "moons" after the Moon. Each of the outer planets is encircled by planetary rings of dust and other small objects except Dionysus.

## Planets

### Inner Planets

The inner Solar System is the region comprising the four terrestrial planets (Mercury, Venus, Earth and Mars) and the asteroid belt. Composed mainly of silicates and metals, the objects of the inner Solar System are relatively close to the Sun; the radius of this entire region is less than the distance between the orbits of Jupiter and Saturn. This region is also within the frost line, which is a little less than 5 AU (about 700 million km) from the Sun.

#### Asteroid Belt

The asteroid belt occupies the orbit between Mars and Jupiter, between 2.3 and 3.3 AU from the Sun. It is thought to be remnants from the Solar System's formation that failed to coalesce because of the gravitational interference of Jupiter. The asteroid belt contains millions of objects over one kilometer in diameter. Despite this, the total mass of the asteroid belt is unlikely to be more than a thousandth of that of Earth. The asteroid belt is very sparsely populated; spacecraft routinely pass through without incident. Several of the Larger Asteroids in the belt are colonized and under heavy mining, most notably being 4 Vesta.

### Outer Planets

The outer region of the Solar System is home to the gas giant planets (Jupiter, Saturn, Uranus and Neptune) and their large moons, The centaurs and many short-period comets also orbit in this region. Due to their greater distance from the Sun, the solid objects in the outer Solar System contain a higher proportion of volatiles, such as water, ammonia, and methane than those of the inner Solar System because the lower temperatures allow these compounds to remain solid.

## Moons

There are 599 discovered moons in the Solar System in which 201 of them orbit planetary bodies and 18 of them being round. The largest moon the system is Ganymede with a radius 2,634.1 km, which makes it larger than the planet Mercury. One of the moons named Europa, harbors indigenous biosphere.

## Life in the Solar System

Solar System is one of the most unique systems in the charted parts of Milky Way Galaxy, because it is only system beside the Relic System and 61 Ursae Majoris System, that has more than two bodies with active biosphere.

### Venus

* *Main Article: **Life on Venus***

Venus, the second planet orbiting the Sun is a hot house with a dense and crushing Carbon-Dioxide atmosphere. Life on Venus was discovered in 2038 during the **Aspiration Mission** to collect atmosphere of Venus. Biodiversity on Venus is at the lowest possible with only two form of microbes discovered to live in the atmosphere of Venus.

### Earth

* *Main Article: **Life on Earth***

Homeworld of Humanity is the only body with life any humans had seen for hundreds of thousands of years. A stable biosphere for nearly 3.5 billion years, Earth has one of the most diverse biospheres known in the galaxy with life on sea, land and air. Earth has been a haven of evolution and life for more than 3.5 billion years and scientists believe that it will be for another 2 billion years.

### Mars

* *Main Article: **Life on Mars***

Mars has the saddest story in the Solar System many would say, for the reason that life went extinct before it had any chance to develop. Evidence of life on Mars was discovered when the samples taken by Perseverance rover were brought back to Earth. Fossils of microbes were found in the samples dating back to 3 billion years ago. With the expansion of Humanity into Mars, further explorations were put into what happened to the life on this body. The youngest fossil that was found on Mars being around 2.99 billion years ago. Scientists believe that the loss of atmosphere during that era led to the disappearance of liquid water and therefor extinction of life.

### Europa

* *Main Article: **Life on Europa***

Europa became the target for the first alien ocean exploration in 2050. Europa mission to explore its subsurface ocean was named Calypso. Calypso was launched from Earth in 2062, arrived on Europa in 2063, drilled into Europa's icy surface and deployed a small submarine named Hesperides. Hesperides found life shortly after. Life on Europa is less complex compared to Earth, but it was also the first place that Humanity found multicellular life. Life on Europa is extremely resilient to radiation emitted from Jupiter and shows heavy bioluminescent properties.

### Enceladus

Enceladus became the next target for humanity's exploration for alien life after the discovery of a vast ecosystem in Europa. Because both moons are ocean worlds, scientists believed that a complex ecosystem may exist in Enceladus as well but after a similar mission to Calypso, it was discovered that only a unicellular ecosystem exist on Enceladus.

### Pluto

Life has never been discovered on Pluto, existing or extinct but scientists discovered major organic activity 100 km deep inside Pluto's crust using advanced scanners in 2210. These bio-signatures still exist to this day. Many scientists believe that a small ocean with a diverse biosphere exist inside the dwarf planet's crust.