Mars

**Mars** (Mars) is the fourth planet from Sol. It was naturally the most terran-like planet in the Sol system, and the 2nd smallest planet in the system. Pre-terraforming, Mars was frequently referred to as the "Red Planet" due to the iron oxide that was present on its surface. Mars is a terrestrial planet with a very thin atmosphere of carbon dioxide. Mars has surface features reminiscent to selena objects, such as Luna, because of its craters, and Terra, due to its ice caps. Mars is also the site of the largest volcano in the Sol system. Mars also has a large ocean-like basin, which is where, post-terraforming, most of the water on the planet resides. This basin was possibly an impact crater of a Saturn-sized object that hit Mars billions of years ago.

Mars strongly resembles Terra in its rotation. The Martian day has about the same duration as the Terran day, and the Martian axial tilt makes seasons roughly identical to Terra's; although Mars's seasons last two times longer, due to its longer year, which also lasts about two terran years. However, pre-terraforming, Mars was uninhabitable in other aspects. Its surface pressure was a laboratory-grade vacuum and its atmosphere was completely unbreathable. Temperature only occasionally rose above 0°C.

Like Venus, the terraforming of Mars was a success. The average temperature of the planet was brought up to 6°C. An entire atmosphere had to be created from Martian sources or brought from elsewhere in the Sol system, ending with about .984 of Terra's atmosphere

## Composition

### Surface

Pre-terraforming, the red-orange appearance of the Martian surface is caused by iron oxide, or rust. The surface itself consists of minerals containing silicon and oxygen, metals, and other elements that typically make up rock. The surface of Mars is primarily composed of basalt.

Mars, along with most terrestrial planets in the Sol system, were subjected to the Late Heavy Bombardment. More than half of the Martian surface shows evidence of this period. there is also an enormous impact basin in the northern hemisphere of the planet. This was probably made by a collision with a Saturn-sized object, creating a basin covering 40% of Mars. This would later serve as the location of Mars's ocean following the terraforming of the planet.

#### Conditions

Martian surface temperatures used to vary from −143 °C at the poles to 35 °C at the equator in the summer. The sparseness of the Martian atmosphere pre-terraforming made major temperature swings akin to Luna. Mars also receives 43% the radiation and light Terra receives. Mars also has the largest dust storms in the Sol system. These can vary from a storm over a small area, to gigantic storms that cover entire faces of planet. However, these storms are not extremely damaging since the surface pressure is very low. Obviously, due to distance from Sol, Mars is the coldest rocky planet in the Sol system.

### Structure

Mars is approximately half the diameter of Terra, and its surface area is only slightly less than the total area of Terra's dry land. Mars is less dense than Terra, having about 15% of Terra's volume and 11% of Terra's mass, resulting in about 38% of Terra's surface gravity.  Like Terra, Mars has differentiated into a metallic core overlaid by less dense materials. The core of Mars is about 1,800 km in radius, consisting mainly of iron. this core is surrounded by a silicate mantle which once drove volcanic and tectonic activity on the planet, but has since died out. The average thickness of the Martian crust is about 50 km.

## Dynamics

### Hydrosphere

Before humans had even existed as a species, Mars is thought to have had a water ocean that covered a third of the planet's surface. Evidence for this ocean include ancient shorelines and the Martian soil itself. Ancient Mars would have needed an atmosphere with a noticeable greenhouse effect to have an ocean this large. It is thought that once Mars lost its magnetosphere, and atmosphere, this ocean sublimated into the atmosphere and was soon lost to interplanetary space, leaving pre-terraformed Mars without an ocean. This all probably took place around 3.8 billion years ago, not even a billion years after the Sol system's complete formation.

### Atmosphere

Mars lost its magnetosphere roughly 4 billion years ago, probably because of collisions with other celestial bodies, leaving the

solar wind from Sol to interact directly with the Martian atmosphere. This meant that Mars's atmosphere would slowly get stripped away. Surface pressure ranges from an extreme low of 0.0003 to an extreme high of 0.01 of Terra's surface pressure. The average surface pressure of Mars was about 0.006 of Terra. Of what atmosphere Mars had, 96% of it was carbon dioxide, 1.93% argon, and 1.89% nitrogen, with the rest being trace amounts of oxygen and water.

### Climate and weather

Mars naturally has the most Terran seasons and day in the Sol system. This is due to the similarity of the two planet's axis of rotation. However, the length of the Martian seasons are twice as long due to the Martian year being twice as long. Wide temperature swings are common place all around the planet due to Mars's thin atmosphere.

Mars nearly has an eccentricity of 0.1, meaning it has a significant effect on climate compared to Terra. When Mars is closest to Sol, it is summer in the southern hemisphere, and when mars is farthest from Sol, it is winter in the southern hemisphere; vice via for the northern hemisphere. As a result, seasons in the southern hemisphere are much more extreme than that of the northern hemisphere.

## Orbit and rotation

Mars's average distance from Sol is about 1.52 AU and has an orbital period of about 687 Terra days. The solar day on Mars is slightly longer than a Terran day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.88 Terra years. Mars has an axial tilt of 25.19 degrees, similiar to Terra's. Although, seasons on Mars last twice as long due to Mars's orbital period.

Mars has a pronounced orbital eccentricity of 0.093. In the Sol system, only the closest and farthest planets from Sol have more eccentricity: Mercury and Janus. About 1.35 million years ago, Mars had an eccentricity which was virtually 0. Like all planets and objects, Mars undergoes cycles that changes its axial tilt, orbital eccentricity, the direction of its axis, inclination, and argument of periapsis. However, this occurs on timescales of thousands of years.

## Moons

### Timor and Metus

Mars has two relatively small natural moons, Timor (Phobos) (about 22 km (14 mi) in diameter) and Metus (Deimos) (about 12 km (7.5 mi) in diameter), which orbit very close to the planet. In all likelihood, they both were probably captured asteroids. Timor itself is a rubble pile and is being torn apart by Martian tidal forces. It is predicted that Timor will break apart into a planetary ring in 40 million years. Both moons are named after sons of Mars, who follow him into battle.

Metus has a carrying capacity (maximum population) of about 3,612 humans, and is made of up about 68.9% water. Since water is by far, the most important commodity off terraformed worlds, Metus is an important port. Due to it's negligible surface gravity, it requires virtually zero delta-V to reach from Mars. The vast majority of Metus's population lives at the main settlement of Timor: Cape Dread.

Cape Dread itself is notably the smallest, but one of the most known asteroid-like settlements in the entire system. Infrastructure in Cape Dread include traffic control complexes, which control all traffic passing by Mars, ship docks, many warehouses, and is the prime hub for trading in between Pluto and Terra. Cape Dread is the stereotypical "Startown", having tourist traps, luxury hotels, pawn shops, bars, and brothels from one end of the city from another. Some parts of the city are red-light districts due to this. Cape Dread itself can produce about 1 metric ton of fuel per hour. Due to the availability of it, metal is used to construct most things, from tools, plates, and furniture. Almost all of the population of Cape Dread lives within 18 km of the center of Cape Dread. The rest of Metus is used for artificial farms or fuel manufacturing. Timor has a similiar settlement: Cape Fear, and has a carrying capacity of 9,510 people. Although Timor has a higher population, it is less wealthy than Metus.

    From the surface of Mars, the motions of Timor and Metus appear different from that of Luna. Timor rises in the west, sets in the east, and rises again in just 11 hours. Deimos, being only just outside synchronous orbit – where the orbital period would match the planet's period of rotation – rises as expected in the east but slowly. A sparse dust ring exists between Timor and Metus.

## Civilization

### History

#### Initial settlement

##### Terraforming

As part of the Gaia program to terraform Venus and Mars itself, humans would first have to change several aspects of Mars to make it habitable for humans.

* Bring up the average temperature to above 0°C.
* Bring up the surface pressure of Mars to near Terra's surface pressure.
* The addition of a breathable, sustainable atmosphere for humans.
* The creation of a artificial magnetosphere.

Moving Mars at the time was unthinkable and would potentially put billions of humans at danger. The Conglomerate opted to heat the planet via a greenhouse effect. Further calculations revealed that a small 4°C increase in temperature would kickstart a runaway greenhouse effect and would make the dry ice in the Martian ice caps evaporate. Rather than crash an asteroid into Mars directly, The Conglomerate decided to instead use orbital mirrors instead.

###### Atmospheric engineering

Mars's atmosphere pre-terraforming was primary composed of unbreathable carbon dioxide, with small amounts of nitrogen and argon. However, the amount of these gases were so low, that Mars was virtually a vacuum. The ideal atmosphere of a terraformed planet would have an atmospheric pressure similiar to Terra and a composition similiar to Terra as well.

The minimum safe breathable partial pressure of oxygen is 16kPa, somewhat less than the partial pressure of oxygen on Terra (21kPa). This would be manufactured carbon dioxide on the poles and below the surface of Mars, which is about 50kPa. And for safety, whatever amount of oxygen is in the atmosphere must be combined with at least as twice as much buffer gas, with ideally four times as much. Nitrogen is not always needed for this, since argon or helium could serve the purpose as well. However, due to nitrogen's availability and importance in Terran life, it was chosen as the buffer gas. The minimum breathable atmosphere on Mars would consist 0.15 atm of oxygen, and 0.31 atm of nitrogen, totaling 0.46 atm in total. Mars has negligible amounts of nitrogen in its atmosphere and regolith, meaning that it had to come from external sources.

Nitrogen would either come from Proserpina, Terra, or Venus. Terra was disqualified due to ethical reasons and possible ecological dangers. Proserpina was not deemed fit for nitrogen extraction also due to ethical reasons and its atmosphere itself makes it stand out from any other moon in the Sol system. The only option left was Venus; and in fact, nitrogen extraction was required from Venus, since even without carbon dioxide, its surface pressure would still be too high for comfort. Nitrogen separation and extraction from the Venusian atmosphere began with the finalization of Venus's orbital ring in 2010 CE. Importation of Venusian nitrogen continued until the final years of terraforming Mars. The importation of the minimum nitrogen would only take about forty years.

Initially, carbon dioxide released into the Martian atmosphere was too high for human habitation, but would easily dissolve into the Martian oceans once they formed. The first stage of terraforming would consist of importation of nitrogen before warming the poles and releasing carbon dioxide.

###### Runaway greenhouse effect

Rather than use extremely strong greenhouse gases, The Conglomerate instead decided to deploy an extremely thin orbital mirror to raise average global temperatures by 4 degrees, which should be enough to heat the dry ice in the Martian poles and trigger a runaway greenhouse effect. The mirror totaled 250 km in diameter and weighed 200,000 tons, meaning it had to be constructed above Mars. This mirror would not orbit Mars, but would hover over it, like Venus's sunshade. To be able to do this, the mirror had to be placed 214,000 km above Mars. By 2030, construction of the mirror had been finished, and the runaway greenhouse effect was initiated soon after.

###### Water and biosphere

The first steps required in the terraforming of Mars, warming the planet and thickening its atmosphere, were accomplished after a few decades. However if left in this condition the planet would remain relatively dry. It is in this, the last major phase of terraforming Mars, during which the hydrosphere is activated, the atmosphere made breathable for advanced plants and primitive animals.

Dropping hydrogen bombs on Mars would eclipse the worst scenarios of nuclear war on Terra, and would possibly spread fallout all around Mars, especially considering the dust storms. Asteroid impacts would be uncontrollable and may hit in the wrong place. The Conglomerate opted to use the same solar mirror that vaporized the poles to volatilize nitrate beds. It would provide 27 TW of power, the same power of a 30 billion ton asteroid hitting Mars, and is much more controllable than an asteroid strike. This mirror was able to provide enough water to cover Mars in 1.1 km deep oceans, reviving Mars's ancient ocean within 30 years. This last stage of terraforming would be complete by 2160 CE and the surface was fit for plant habitation. With large-scale importation of plant life, by 2210 CE, the atmosphere and climate of Mars and Terra are almost identical, although the Martian atmosphere is 40% thinner than Terra's.

###### Magnetic field

With the main terraforming finished, there left a minor issue: Mars's magnetic field. Although Mars has regional magnetic fields, it is not enough to be noticeable. Without a magnetic field, Mars would lose its atmosphere on geological timescales and cancer rates may be higher on Mars without it. This was easily solved with the construction of a set of Motojima rings. The ring system itself was composed of 12 rings around Mars, powered each by a 0.6 GW fusion power plant constantly. Totaling 7.2 GW of constant power. The construction of the Martian Motojima was finished by 2132 CE.

#### Economy and human geography

Like most terraformed planets, most of which have high populations, Mars is self-sufficient and is able to support itself. Due to this self-sufficiency and high population, Mars does not focus on a single economic aspect and has a wide array of industries. Due to Mars position and the economic importance of Metus, most ship often stop at Mars before heading out into the outer Sol system, especially to restock on fuel or water.