Whether or not there was life on Mars in the past, there can be life on Mars in the future!
I am talking about transplanted Earth life: people, plants and animals. Mars has every chemical element needed to live. It also has solar energy, gravity, and a reasonable 24:40 day.
Mars is the best place to set up the first permanent settlement beyond Earth. Since Mars has an atmosphere, it is forgiving of air-leaks. If you lose a little air, you can extract some more from the Mars atmosphere with simple machinery. Compare Mars to Luna (also know as "the" moon, by Earth dwellers who can not see the dozens of other moons). Luna lacks water, hydrogen, carbon, and nitrogen. So if your Lunar habitat loses some air, most of it has to be replaced by imports from Earth. (Oxygen can be squeezed from the Lunar soil, but it is more difficult than extracting oxygen from Martian CO2.) Also, Lunar nights are very long and cold, thus it is hard to grow food crops.
Incidentally, free floating space habitats made from asteroids are the best place for large scale human settlements. After we learn to process materials in zero-G and control air leaks, the asteroids will provide essentially unlimited materials and solar energy.
Mars, however, is still a hard place to start building. It is a bit cold. The air is thin. Transportation costs for materials and tools from Earth are, well, "astronomical". To contain the costs, we must make maximum use of local building materials: dirt and rock. We should also use simple building techniques, so that the tools can be simple and reliable, and so we can improvise quickly.
The lack of building materials on Mars would be a problem for aerospace engineers and architects from developed countries who normally design with aluminum, wood, cement, steel, plastic, and composites. One building material can be easily made from raw dirt: bricks. Just put dirt in a mold, compress it, and microwave or heat it - you get a brick. For living quarters, the first group of people on Mars could build brick vaults (with help from simple robots and tractors).
I showed dozens of pictures of Earth buildings suitable for Mars. Conclusion: We have thousands of years of building experience to draw from. And, the Mars brick buildings can be very permanent, some Roman buildings are still standing.
First Habitats - Barrel Vaults
The first people on Mars would temporarily live in a couple space-station type modules or Zubrin's Tuna Can. They would build permanent buildings patterned after the Roman barrel vaults. This design is a series of 2 story brick vaults built in a trench, 6 meters high, 8 meters across, and 20 meters long. It is intended for 4 people. The upper floor lofts have bedrooms and bathrooms. One end of the lower floor has a living room, kitchen with eating area, and small plant growing area. The other end has offices, utility rooms, and a workshop. The internal air pressure would be 700 millibars, with 30% oxygen plus argon and nitrogen as buffer gasses.
However, bricks have no tensile strength. The real purpose of a brick vault to hold the shape of the habitat, especially when it is depressurized. So, the building must covered with 8 meters of regolith (dirt) to resist the internal air pressure. This covering also evens out the day-night temperature differences and protects from radiation.
Glazed brick and a plastic liner on the inside keeps air and water vapor from leaking through the brick wall. To protect the plastic, the walls are hung with used parachute cloth, preprinted with selected murals and wallpaper patterns. Above the brick ceiling, a layer of sand and another sheet of plastic serve to catch any air from leaks. Any leaking air is continuously pumped out to be recycled (i.e., into a greenhouse). The ground floor is also built of alternating layers of sand and plastic, topped with a paving of surplus bricks.
The second floor loft is constructed as materials become available: sections of spacecraft aeroshells or other scrap metal, bamboo grown for the purpose, or fiberglass produced on Mars. The loft is supported on brick walls and columns, and by tether material hung from the ceiling.
A surprising number of furnishings can be made or scavenged on Mars, such as: pottery bowls, built-in brick benches, masonry tables, mattresses of parachute cloth stuffed with leaves, water purifiers using soil filtration. Wires, tubes, tanks, electric motors, and electronics would be reused from spacecraft.
Later, a large Martian colony could construct large multi-story masonry structures. Sketches were shown for a series of buildings, each as large as a city block (55 meters by a few 100 meters). They are separated from each other by shear walls and emergency air-locks. The upper floors have apartments with back-yard gardens. Other floors contain laboratories, offices, stores, and workshops. All open onto balconies overlooking a spacious atrium with sun-lit windows on the other side.
They are built from stone quarried underground to make additional chambers. These buildings would have significant savings in excavation and heating costs over the smaller buildings. Such structures still would not require metal or composite building materials, so they can be built before an industrial base is established on Mars.
No Deposit, No Return
There are 2 basic reasons to go to Mars:
- Science - to study geology, meteorology, biology.
- To Live on Mars - Mars is a likely second home for us.
If half the reason to go is to stay on Mars; then we should assume we can stay, and try it.
A major cost and risk of Mars missions is bringing the people back to Earth. In Zubrin's Mars Direct plan, one of every 2 launches was devoted to the Earth return vehicle and its fuel manufacture. And, the most dangerous time may be liftoff from Mars in a relatively untested rocket which has been sitting on Mars for 4 years with minimal maintenance. Other mission plans have similar high cost and risk for the return trip.
The life support systems you would have used for the long trip home could support you while you build simple building, such as these brick structures. Rather than taking fuel for the return trip, take tools and extra inflatable greenhouses. Suddenly, after the first mission, you have a permanent base.
Obviously, we will not send people to Mars without the ability for them to get home. But that capability can be held in reserve and used in other ways later. Faced with half-year return trips and launch windows every two years, the new Martian would be safer to stay on Mars, then to risk a return trip to Earth.
It would be the ultimate irony to never colonize Mars or anywhere else, simply because it was too expensive to insure safe passage back to Earth.
We already know how to build buildings for Mars, specifically buried brick vaults. The bricks could be manufactured easily from Martian dust, more easily any material with good tensile strength such as aluminum. The construction equipment and techniques should be simple and 'low-tech', to allow for flexibility and repair. We should plan to set up a permanent Martian base during the first and second manned Mars mission. The savings of fuel and equipment for the return trips will pay for the extra equipment and supplies needed.