Mars is like Northern Canada, but worse

Sunday, January 14th, 2018

Colonizing Venus may be oddly feasible, because its dense atmosphere lends itself to floating cities. Colonizing Mars presents a very different challenge, as Matter Beam explains:

Atmospheric pressure is 1% of that on Earth. It is mostly unbreathable carbon dioxide, and does a poor job of spreading the warmth from half the sunlight we are accustomed to. Temperatures ranges from -135 degrees Celsius to an infrequent 35 degrees Celsius, averaging -55 degrees Celsius to Earth’s 14 degrees. Dust storms sometimes fill the sky, but their main effect seems to be eroding the ancient geological features over a surface area equal to Earth’s landmass.

The planet is also long dead. Most of the core is no longer molten, meaning that it does not spin to generate a magnetic field. Being 15% of Earth’s size, it cooled down to its present state much quicker.

Despite its downsides, Mars is pretty hospitable compared to other planets in the Solar System. It is cold, but no unmanageably so. It has a lot of solid, traversable ground. The polar caps contain billions of tons of water ice covered by a layer of solid carbon dioxide. The soil can be used for agriculture after some preparation.

Martian gravity is 37.6% of that on Earth. It is doubtful whether this is enough to stave off the muscle atrophy and bone loss caused by prolonged living in low or micro-gravity.

The low atmospheric pressure means that most architecture and equipment on Mars will have to be hermetically sealed and pressurized. This imposes structural constraints and a dangerous failure mode if the colony’s walls are pierced. Obtaining breathable gasses might requires energy and time: oxygen can be removed from carbon dioxide by energy-hungry chemical reactions, of through the photosynthesis of plants. Nitrogen is present at a 1.0% concentration in the thin Martian air, so it can eventually be extracted for small colonies to use as fertilizer and breathing mix. Larger colonies would need to find it in the soil, either as NO3 or NO.

The atmosphere actually helps with the cold, as it is so thin that lacks the ability to conduct heat away from the colony. It acts as an insulator. This makes dealing with Mars’s low temperatures easier than on Earth, where a thick atmosphere steals heat away from buildings in Antarctica or Northern Canada much more quickly.

Mars’s greatest assets, Matter Beam explains, may be its two moons: Phobos and Deimos.

Let’s start with Phobos.

The closest description would be a floating pile of rubble, loosely held together by a layer of compacted dust. It is composed mainly of carbonaceous chondrite rock riddled with ices and crevasses that might take up to a third of its volume. What is it good for? Living and lifting.

Phobos has a surface gravity of about 0.0004g. Riding a bicycle on the Mars-facing side is enough to fall off the moon and start orbiting Mars instead. It also means that it is very easy to dig into Phobos and excavate large volumes. These volumes can be filled with orbital habitats. These will have access to large quantities of volatiles and minerals, and the surrounding rock will provide sufficient radiation protection.

At 6000km, Phobos is also close enough to start considering orbital elevators. A cable can be dropped from the moon to an altitude of about 10km. In the simplest version, it passes over the surface at 2662 km/h. A mass-driver launched spacecraft or even a supersonic aircraft can catch up to the cable. The Martian end of the cable experiences nearly no drag, so it doesn’t heat up. Structural requirements are so low that it can be built from existing materials such as Zylon. It only needs to be about 12 times heavier than the payloads it expects to receive.

Once the aircraft or pod is attached, it simply climbs up to Phobos with no propellant required. This is a ‘free’ 4.1km/s of deltaV.

A more advanced version has an equally long cable extending out from Phobos. The two cables rotate in opposite directions to the moon’s orbit, allowing the lower end to nearly cancel its velocity, while the higher end travels at twice the orbital velocity.

The advanced version allows Phobos to ‘pick up’ payloads from the surface, then fling it outwards on the opposite end. At 4km/s, it can impart enough velocity to fling a payload all the way to Earth. In reverse, it can capture a spaceship entering the Martian system, and deposit it gently onto the surface at the other end.

A cable system vastly cheapens travel to and from Mars’s surface, Mars’s moons and extramartian destinations. Mars might end up being an even easier destination than Venus with its aerocapture or Mercury with its beamed solar power. Thanks to low surface gravity and thin atmosphere, the cables can be made from conventional materials and do not require much protection.

Deimos is a more extreme version of Phobos.

It is even smaller and higher than Phobos, but nearly identical in every other way. With a cable system, it can capture interplanetary spacecraft and lower them to Mars’s surface or Phobos’s orbit even more cheaply in terms of deltaV saved, energy required and structural mass involved.

So, by properly exploiting its moons instead of relying only on the surface, Mars becomes a very inviting destination for spacecraft. While it lacks the energy to produce or refine products cheaply, it can compensate by providing rocket fuel and sending off the products to other destinations at greatly reduced deltaV cost.

I was not expecting that.


  1. Jim says:

    During a solar flare an individual in the open on Mars could be killed by the radiation. Certainly Antarctica is far more promising for human settlement.

    Maybe global warming will turn Siberia into a wonderful place to live.

  2. Slovenian Guest says:

    This reminded me of the The Earth-Moon Tunnel!

Leave a Reply