Before one can consider the terraforming of Mars, it is necessary to examine what kind of materials and technology would be needed to actually get all of the necessary materials to the planet to begin the process. Controversies in the field have focused on two aspects of materials transport to Mars:
Should the space ship land on the Moon before continuing to Mars? If so, would that mean we would have to colonize the moon before colonizing Mars?
How can we take a ship to Mars with enough fuel to return without having outrageous mission costs?
Moon Detour
To the first question, the answer is likely a resounding “no”. The moon, while closer, has a much thinner atmosphere, and thus the fuel required to brake a space ship landing on the moon is more than the fuel required to brake one landing on Mars. This is not to mention the fuel needed to lift the space ship off of the Moon after landing upon it. Since the moon does not contain resources that could be easily transformed into rocket fuel, it is impractical for the Mars-bound space ship to stop at the moon to refuel before continuing to Mars.
The answer to the second part of the first question is less clear. Would it be useful to colonize the Moon before we begin to colonize Mars, whether or not it is useful to make a pit-stop there on the way to Mars in the future? Some say that if we were to making a bubble community (or one in which everything is confined within a biosphere), the Moon would be the best choice by far given its proximity to the Earth.1 However, if indeed we could transform the surface of the planet so that biospheres are not required to sustain life on the planet, then Mars becomes the most alluring and most practical planet to explore. It may be necessary to build biosphere communities before we begin to terraform the planet, which would make a bit of a case for beginning with the Moon as a sort of practice run. However, with the Moon’s non-existent atmosphere and sparse resources, some have commented that it is more practical to land on and colonize Mars as a practice run for doing the same on the less hospitable surface of the Moon.2
Fuel Limitations
In answer to the second question, can we take enough fuel to Mars to enable its return without outrageous mission costs, the answer is probably not. With the traditional rocket fuel that we have been using, the costs of launching and flying the large, heavy space ship required to transport that amount of fuel would be enormous. However, recent leaps in propulsion technology may bring this idea closer to the realm of possibility. Work has been done with nuclear engines, like the one currently being used to explore Pluto. The Planetary Society designed and launched a prototype for a kind of propulsion known as the Solar Sail. A solar sail is a small spacecraft with extremely large wings (the prototype’s wings were 10 stories high!) which is propelled with the energy of photons coming from the sun. A much larger sail could be used for interplanetary travel. While it would accelerate very slowly, it would eliminate the necessity of bursts of rocket fuel, changing its course by a slight adjustment of the orientation of the sail, just like a sailboat on the ocean.3 However, rocket fuel would still be needed for the entry into the Martian atmosphere and the lift-off from the Martian surface.
One idea, proposed by the Mars Society, would be to travel to Mars using rocket fuel from the Earth, and once there, to create rocket fuel using resources found on the Martian surface and in the atmosphere.2 The president of the International Mars Society, Robert Zubrin, contracted with Lockheed Martin and the Johnson Space Center in the early 90s to create an engine that would create its own rocket fuel, using hydrogen brought from home (the lightest component of rocket fuel, comprising only 5% of its weight) and carbon dioxide from the Martian atmosphere to create methane and oxygen, the two components needed for rocket fuel. It would use the Sabatier Process first proposed for use on Mars by William Dowler, Robert Ash, and Guilio Varsi.4
This plan would not only alleviate the need for bringing heavy rocket fuel from the Earth, it would also get rid of the inherent danger in trying to land on the surface of Mars with a gigantic store of rocket fuel on board. This might open up the possibility of a semi-soft landing into the planet with airbags instead of a soft landing like the lunar landers which drives up the cost of the mission. The idea would be to send a robotic mission with an engine capable of synthesizing rocket fuel in advance of human explorers, that way the rocket fuel would be ready and waiting for the astronauts to arrive. If the engine encountered problems making the rocket fuel, the launch of the manned space craft could simply be delayed until the problems were fixed. This is part of Zubrin’s Mars Direct plan for Mars colonization, which received some attention from NASA but has since been partially abandoned in favor of today’s robotic exploration missions spearheaded by Jet Propulsion Laboratory. Zubrin’s ideas about a manned mission to Mars may be coming back into favor, however, as NASA begins to shift gears and pour a great deal of its funding into manned missions as is proscribed by new government policy.
So far the Mars Direct plan has been modified slightly to get rid of what scientists believe may be its weakest link: the Mars Direct plan calls for the Earth Return Vehicle (ERV) to be the same puck-shaped module that will land the astronauts on the surface. In the plan it is the lander (equipped with wheels to move it around the Martian surface like a rover) that will carry the astronauts back to the Earth. NASA later decided that the ERV would be much too small a space for the 4-6 astronauts to inhabit on their 6 month journey back to the Earth, and that such confinement may result in strain and bickering at the best, and at the worst, madness.4 The new plan proposes that a larger ERV be left in Mars orbit while the team roves the surface, after which a small Mars Ascent Vehicle could be used to get back into Mars orbit where the team could dock with the ERV and return home. This plan has been criticized for the increased risk that docking introduces into the homecoming process. Some experiments have been done in Antarctica and other isolated places by the supporters of the Mars Direct plan to see the effects of confinement and isolation on the sanity of human beings.2
Though the majority of these programs were cancelled and the organizations that put them together thrown in the scrap-pile of NASA history, the future of manned flight to Mars is far from over. Funding is coming back to piloted space flight, and new technology such as SETV (Solar-Electric Transfer Vehicle) which uses new ideas pioneered by the Russians to provide energy to Mars-bound spacecraft without ever leaving low-Earth orbit. This technology, coupled with the new technique of using aerobraking (braking by skimming the atmosphere of Mars repeatedly, a technique even now being used by the newest Mars orbiter), could drastically reduce the amount of fuel needed to reach Mars, and therefore eliminate the possible political nightmare of a nuclear-powered launch as well as lightening the weight of the rocket and thus its cost. As new technologies are developed, the cost of the manned Mars program is plummeting. No longer is a trip to Mars the unimaginable $400 billion venture that was once estimated- the Mars Direct program brings the cost to under $50 billion and the new technology available brings the price down even farther. Eventually, travel to and from Mars could take place every 24 months during the Mars launch window. New teams could make use of housing and fuel left by previous teams. Eventually, our continued presence on Mars could open the door for a long-lasting program that could lead to the terraforming of Mars.