Mars
Position on the route: 4/45 · level needed 10 · journey (Mk0 engine) 5.4 h
By the numbers
| Distance | 55–400 million km |
|---|---|
| Diameter | 6,779 km |
| Gravity | 3.71 m/s² (0.38 g) |
| Day (sol) | 24 h 37 min |
| Year | 687 days |
| Mean temperature | −63 °C |
| Atmosphere | 95 % CO₂, 6 mbar |
| Moons | Phobos, Deimos |
The story
The planet with the most Earth-like day in the solar system: a sol lasts 24 hours 37 minutes. But the atmosphere is a hundredth of Earth’s and almost all carbon dioxide; liquid water cannot stay on the surface, it boils away or freezes. The polar caps hold water and dry ice, and wide layers of ice lie just under the surface.
Olympus Mons is the tallest mountain in the system at 21.9 km, Valles Marineris a canyon 4,000 km long. The soil holds perchlorate salts: toxic, but a source of oxygen with chemistry. The MOXIE experiment (Perseverance, 2021) proved oxygen can be made from Martian air.
Global dust storms can last months and blot out solar panels (the Opportunity rover fell silent that way in 2018). A serious colony therefore needs nuclear power or large storage. Radiation is about fifty times Earth’s; habitats are covered with soil or built in lava tubes.
Missions
- Mariner 4 (1965): first close-up pictures
- Viking 1–2 (1976): first successful landings
- Sojourner (1997), Spirit and Opportunity (2004)
- Curiosity (2012–): Gale crater, an ancient lake bed
- Perseverance and Ingenuity (2021): sample caching, the first helicopter
- Zhurong (2021): China’s first Mars rover
Colony note
The second great goal. Water ice, fuel from CO₂ (Sabatier), a 24.6-hour day. The hard parts: thin air, radiation, dust storms, a 6–9 month journey.
What probes bring back
- 0.5–1 % perchlorate in the soil: toxic, but a source of oxygen.
- A wide layer of water ice a metre under the surface (radar).
- Oxygen made from the air: the MOXIE experiment, 6 g an hour (2021).
- Seasonal methane measured; its source is debated.
- A global dust storm: sunlight fell by 90 %.