Despite the fact that images from the surface of Mars often show a landscape that is surprisingly Earth-like, this analogy is very superficial and misleading, and in actual fact, as a candidate for colonization, Mars has a number of serious drawbacks.
Firstly, the gravitational strength is only about 0.38 Earth gravity. Long term effects of this are not known exactly, but they have to be assumed to be serious enough to preclude long term habitation on the Martian surface without some artificial gravitation technology. Furthermore, the atmosphere is very thin and pressure suits are required on the surface at all times. There is no magnetosphere and radiation levels are high and the soil itself is generally toxic. The thin atmosphere provides little protection from meteor strikes, which are significantly more frequent on Mars than on Earth, given Mars's proximity to the asteroid belt.
But these problems only begin after you have got to Mars, which is a journey of about 6 months by conventional chemical rocket propulsion, with a window about every two years for such a transfer trajectory. A Mars colony would be much more isolated than one on Venus for example, and even as a base for exploring the Asteroid Belt or the outer Solar System, it is not particularly useful given its slow rotation around the Sun.
A Mars mission which would send a team of astronauts to Mars for 6 months as part of a 2 year round trip, using basic habitats on Mars, would be physically extremely arduous and dangerous, the chances of survival would not be good. IST does not remotely entertain the idea of such risky endeavours and does not propose any voyage to Mars until the above problems have been fully solved. Once that is the case, the advantages that Mars has as an interplanetary destination become quite interesting.
Firstly, being much smaller than Earth, the delta-v budget to Low Mars Orbit from its surface is only 4.1 Km/s. A small spacecraft weighing about 3 tons empty and with a takeoff weight of 16 tons could carry 1 ton to LMO, using a rocket with an Isp of only 300 s. Using LOX/LH2, a 2 stage craft with suborbital rendezvous at apoares could take about 2 tons to LMO without using aerobrake to decelerate either stage through more than about 0.5 Km/s which would not require special heat resistant materials, and greatly increase the reusability of the craft.
Mars is rich in volatiles and various metallic minerals. All sorts of manufacturing can take place on Mars without importing any raw materials. Mainly for reasons of safety, development of facilities on Mars is best done underground. Martian gravity is strong enough that fairly conventional boring and tunnelling techniques can be used to create extensive underground excavations. There are no Mars quakes to worry about, although the internal spaces will be very cold, and require strong thermal insulation.
Underground rotating habitats will be where astronauts spend most time when accommodated on the planet. These will require substantial heavy industry to build, hence in the initial stages, personnel will spend most of there time in rotating space stations. Spending 3 weeks in orbit for each week on the surface at 0.38 G should prevent any significant health problems due to low gravity over a period of two years.
The journey to and from Mars, even in the earliest stages of Mars exploration, must be concerned primarily with astronaut safety. It may seem that the choices for pioneering missions to Mars, involving 6 months or more in zero gravity, are inherently dangerous, and a high degree of risk compared to other flight regimes must be accepted. IST does not share that view. Although in the very earliest stages it may be difficult to make interplanetary flight to and from Mars as safe as Cis-Lunar operations, much can be done to reduce the risk difference to very small margins. Firstly, IST does not intend to attempt manned missions to Mars until there is a substantial Cis-Lunar economy, and substantial infrastructure has been sent to Mars by autonomous craft. This will enable the design of spacecraft for manned missions to Mars to include many safety features, including redundancy in key systems that would be too heavy for a mission depending on all material being lifted from Earth's surface. Also, astronauts arriving at Mars will have a full Earth gravity environment in which to recover for some time before starting any physically demanding activities. Secondly, any craft travelling to and from Mars will be accompanied by at least two autonomous craft, which will travel in a similar transfer trajectory but far enough apart so that there is no risk of collision. These craft will have enough capacity and resources to cope with any foreseeable emergency on the main craft, including the main craft being abandoned hurriedly. The shepherd can rendezvous with the main craft in a matter of a few days at most and if necessary recover the entire crew, who could be surviving in emergency inflatable life support systems. In the event of the manned vessel being stuck in space if both shepherd craft fail, further rescue craft could be dispatched from Earth or Mars, whichever is closest
These safety features will significantly increase the cost of interplanetary travel to and from Mars, however, IST believes it will be well spent and that all pioneering flights to Mars and back will be accomplished without loss of life. Similar safety precautions will be taken in the succeeding phases of Mars exploration. The vessels used for phase 2 of travel to Mars and back will be like simplified rotating space stations. They will travel in a continuous fashion between Earth and Mars with propulsion stages attaching and detaching to provide boost where required along the trajectory. As LH2/LOX fuel will be cheap at this phase of space exploration, travel times to Mars will be reduced by using multiple boost stages to as little as 3 months. Looking to the long term future, IST intends to experiment with various augmented solar sail technologies, firstly to propel cargo autonomously between Earth and Mars, and then adapt if possible advanced forms of laser pushed sail technology to interplanetary travel. This technology is usually associated with space journeys measured in 100s of Astronomical Units. A laser pushed sail that could push a craft with a total weight of about 50 tons with a 1 G acceleration would require a laser source of about 200 Terawatts. This may seem a huge amount of power and even if achievable, unnecessary for a journey to Mars and back. IST likes to think big, such a craft could get to Mars in less than a day. Building and operating such technology over a relatively short distance would be excellent preparation for using such technology in more challenging operations, namely travel to the Outer Solar System and beyond.
IST then envisages three phases of Mars development. A preliminary phase of autonomous transport of infrastructure materials to Mars orbit. Manned flight to Mars will be required to consolidate this preliminary phase. Simple but effective artificial gravity will initially be provided by tethered pods both on the interplanetary travel phase and in orbit around Mars with the top priority being the construction of a least 3 full 1 G rotating space stations in Mars Orbit. Phase 1 will develop travel to and from Mars in large rotating craft, development of Mars surface infrastructure including the construction of underground rotating habitats with full Earth gravity. At this stage Mars will also be the base for detailed survey work of the entire Asteroid Belt as it rotates around in a 2 year period. Phase 2 will see the development of laser pushed sail technology between Earth and Mars, large scale asteroid mining operations and a Mars population of about 1 million persons.