Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
SAF Archives  search ask the scientists in the classroom cool science
scientists from previous shows
cool careers in science
ask the scientists

Photo of Robert Zubrin Journey to Mars:
Out of Thin Air

Robert Zubrin

q I would like to know some more exact specifications on the system you developed to make fuel on Mars. What goes into the system, what chemical reactions occur and what is the final product?

A There are a number of ways to run the system. One way is to have hydrogen (taken from Earth) and carbon dioxide (taken from the Martian atmosphere) go in, and react to form methane and water. We then store the methane to use as fuel, and electrolyze the water, which makes oxygen (oxydizer needed to burn the fuel) and hydrogen, which is recycled back into the machine to react again. The net product of this cycle is thus methane and oxygen.

Another way to run the machine is to use a different catalyst (copper on alumina instead of ruthenium on alumina) which will cause the hydrogen and carbon dioxide to react to make carbon monoxide and water. The water is electrolyzed to produce oxygen and hydrogen, as before. The carbon monoxide is reacted with more hydrogen in a second (copper on zinc oxide) reactor to make methanol. The net product of this cycle is thus methanol and oxygen.

q How did you first get the idea to create rocket fuel on Mars? Then what kinds of experiments did you have to do to make your idea work?

A I got it by studying the history of past explorers on Earth: all the ones that succeeded used a "live off the land" strategy.

Then what kinds of experiments did you have to do to make your idea work?

The first experiment we did was to build a machine that could make methane and oxygen gas out of carbon dioxide and hydrogen, and described in the first part of my answer to question #1 (titled specifications of the system). Then we added pumps and refrigerators so we could compress carbon dioxide from the kind of low pressures it is found in on Mars, and also allowing us to liquefy the methane and oxygen produced so they could be stored. Then I built another machine that could make methanol and oxygen, as described in the second part of my answer to question #1.

q How large is the refueling tank on Mars? How much fuel can it hold? About how long do you estimate it will take for the refueling tank to get to full capacity?

A The tanks on my Earth Return Vehicle are about 120 cubic meters in volume, and can hold 24 tonnes of liquid methane and 84 tonnes of liquid oxygen. It would take 10 months to fill it up. This occurs while it is on Mars waiting for the next launch window to open up for the crew to fly out to meet it.

q Could we use your fuel system here on earth to create energy and take excess carbon dioxide out of the air?

A You could use it to take some carbon dioxide out of the air, but it would not create energy. It takes energy to make it run. Of course, there are some places where energy might be cheap, say at hydroelectric plants in the Pacific Northwest or at solar power stations in the middle of a desert. The system could be used there to make portable fuels that could allow us to transport the energy elsewhere.

q Robert Zubrin's book "The Case for Mars" argues for creating artificial gravity by spinning the Mars-bound crew ship on a tether. Does NASA plan to test the feasibility of artificial gravity, as a way to eliminate the health effects of a long period of microgravity?

A There are no such plans right now, but there should be.

q Why isn't the space program as popular as it was in the 1950's and 60's? Is it the bad publicity? The cost? When I was a kid in the 70's, many teachers were confident that space travel for the masses would be common in our (the kids') lifetimes. Now those same kids are approaching 30, and that dream seems to have degenerated to Star Trek re-runs. What gave those teachers such confidence in the speed of technological development? It seems to me that at this rate, those raccoons you mentioned will beat us to Mars.

A The problem is that since the 1970's the US space program has not had a real goal, and as a result it has made very little progress. We need a central motivating goal to drive our space program forward. That goal should be the human exploration and settlement of Mars.

q I am designing a Mars colony for science class. Is there a way to use the dust storms/wind on Mars to turn a turbine to create electricity for a colony?

A In principle yes, but since the Martian air is very thin, its hard to get much power. Nuclear or geothermal power are more promising.

q How would you choose a spot on Mars to start a new settlement? And how do you take precautions so won't land on uneven ground?

A I would send a human crew to Mars to explore a wide region, and use on-the-spot surveys to choose the best location for a permanent base.

q The costs that you give for a humans-to-Mars program are similar to what the U.S. spent to send humans to the Moon. But after six Moon landings Congress decided that the costs were too high, and it has been over twenty years since a human last stood on the Moon. Is it worth going to Mars if the pattern -- a few successful missions, followed by decades of inactivity -- is going to repeat itself? How can a humans-to-Mars program become affordable?

A The way to make a humans to Mars program worthwhile is to establish from the beginning that its purpose is to pioneer Mars for human settlement. The Moon program went off the track because the politicians believed that its purpose was to beat the Soviet Union to the Moon. That may have been its purpose FOR THEM, but it was not its true purpose for human history. If people understand why going to Mars is important -- opening a new world for humanity -- then the program will fulfill its purpose.

q I have heard that you recently founded an organization called the Mars Society. Can you please tell me more about this organization, its purpose and how one could join?

A The purpose of the Mars Society is to push forward the exploration and settlement of Mars by both public and private means. We have over 70 local chapters -- 50 in the USA and 20 in other countries. We are mobilizing political support to get the governments to do more to open Mars, and at the same time we are starting a series of escalating projects of our own, each of which is designed to earn us the credibility required to undertake a more ambitious project in the future. Our first project is to build a simulated human Mars exploration base in the Canadian Arctic. Anyone can join the Mars Society, including students. Our Founding Convention was held in Boulder Colorado in August 1998, and 700 people came, from all over the world, and 180 of them gave talks. Our next convention will be in August 1999, also in Boulder. Complete information about the Mars Society can be found on our web site at

q In designing a colony on mars, providing water could be a serious problem. Do you have ideas about how to supply water for the colony -- perhaps from the polar ice cap on Mars?

A Yes. Water can be extracted from the soil by baking it out, as Mars soil tested by Viking landers was shown to be 1 to 2% water. A better way would be to find liquid water underground, and drill for it. Ice is available at the north pole, and may be available much further south on the north side of hills. Many ways to access water are discussed in my book "The Case for Mars."

q Why are we trying to colonize Mars when we haven't even tried to colonize the moon? And why Mars instead of another planet?

A The reason why we should try to colonize Mars first is because Mars, unlike the Moon, possesses all the resources needed to support life and civilization. The Moon has very little water, Mars has amounts that could fill oceans. Mars has carbon and nitrogen, the Moon does not. Mars has a 24 hour day, which is what plants need to grow, but the Moon has 2 weeks of light followed by 2 weeks of dark. Mars has an atmosphere, the Moon doesn't. In every respect but distance, Mars is a better target for colonization than the Moon. If we compare the Moon and Mars to possible destinations in Earth's past age of exploration, the Moon is like Greenland -- close to Europe but barren of resources. Mars is like North America -- further away but much richer in resources and thus a place where a new civilization could really be built.

q If your Mars Direct plan is a success, do you plan on retiring? Or will you come up with plans to go to another planet or create other inventions?

A IF Mars Direct is a success, I plan on doing everything I can to help further the colonization of the Red Planet. I don't plan to retire until I can retire on Mars.


Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.