NASA’s recent announcement that methane -oxygen propulsion would no longer be a requirement for the Crew Exploration Vehicle (CEV) has created great concern in the space community that the agency’s commitment to the human exploration of Mars might be waning.

Because methane -oxygen can be readily manufactured on the surface of Mars out of local materials, it is the ideal propellant combination for Mars ascent propulsion. Its earlier prescribed development as part of the CEV program was therefore widely seen as evidence that the CEV was being pursued not merely as a thing in itself, but as part of a broader vision that would take America all the way to Mars. Its abandonment has therefore been interpreted as indicating the collapse of that vision.

In some respects, this dark view is overdrawn. NASA’s exploration office remains committed to the development of a heavy-lift launch vehicle, which is the primary hardware element needed for a human Mars mission. As far as methane-oxygen propulsion is concerned, two contracts were recently awarded by NASA supporting its development outside of the CEV program, and should that technology be employed for lunar ascent but not CEV, that would still be timely enough to prepare it for Mars application.

Yet it must be said that the dropping of methane -oxygen from CEV, while not a fatal blow in itself, illustrates a dangerous trend that could well destroy the human exploration program. It is always easier to conduct any technology development program with a view towards meeting only immediate mission requirements, while ignoring those needed for evolutionary application.

This, in fact, is why methane -oxygen was dropped from CEV. Methane-oxygen offers superior performance to conventional storables on CEV itself, and becomes increasingly advantageous as applications for first lunar ascent and then Mars ascent are brought into play. However in order to reduce immediate costs, its development has been deferred.

Now let us consider the lunar program that is supposed to follow CEV. It will, perforce, be cheaper in the short term to design human lunar exploration systems without regard for potential application to Mars. Thus a NASA adopting the view that it is best to solve one problem at a time will be driven in precisely that direction. The net result will be a Moon program that is just a Moon program, and not, as President George W. Bush specified in his national security document authorizing the Vision for Space Exploration, a Moon-Mars program in which lunar activities are conducted in order to “develop and test new approaches, technologies and systems … to support sustained human exploration to Mars and other destinations.”

The consequences of allowing the vision to be degraded in this way would be grave. This is made nowhere more clear than in an op-ed article by Paul Spudis, senior research scientist at Johns Hopkins University’s Applied Physics Lab, that was published in the Dec. 27 edition of the Washington Post advocating precisely such a course.

A noted lunar geologist and space policy insider, Spudis’ article is of great clinical interest because he is the most eloquent and informed advocate of a Moon-only vision for NASA. He argues that such a program could be justified on three grounds:

First, that studying lunar cratering will allow us to understand the processes of mass extinctions on Earth;

Second, that Lunar activities will provide us with practice for exploration of “other worlds;” and

Third, the Moon base will provide an economic return by enabling the development of lunar solar power stations that will beam electricity back to Earth.

However, these programmatic foundations have no basis.

Argument one is false because the Moon’s lower gravity gives it a lower impact rate than the Earth, and its lack of an atmosphere or biosphere makes impossible any studies of the relevant post-impact terrestrial phenomenon that cause and shape mass extinction.

Argument two is false because while we can practice for operating on other worlds on the Moon, we can do much more in that line at 1/1000 the cost in the Arctic.

Argument three is false because a photovoltaic panel only receives twice the solar flux on the Moon as it does in Arizona, and all of its increased output would be lost in the inefficiencies of the transmission system. Thus the useful output of a photovoltaic power station on the Moon would only be equal to one on Earth, while logistics costs to support it would be 100,000 times as great. Furthermore, the station would be blacked out two weeks at a time, and require three receiving rectenna and power distribution systems on Earth as well, each of which would be blacked out two-thirds of the day during the half of the month that the station produced any power at all.

In short, the programmatic justifications offered by the ablest advocate of a Moon-only vision have no valid basis at all. Under favorable political conditions, NASA might get by for a while by having its supporters chant such nonsense to entertain Congress, in the same manner as it used similar unsound “rationales” to justify the shuttle and space station programs. However, at the end of the day little of real value will have been accomplished at great expense.

The shuttle and station programs initially were proposed as bridges to an expansive evolutionary future. Yet because of design compromises to save costs on the programs themselves, without regard to how they would really serve a useful role supporting human exploration beyond low Earth orbit, neither have any such utility, and NASA’s primary current concern with these programs is how to escape from them so it can get on with its mission.

Again, it was precisely because the design of the shuttle and station had been effectively detached from the need to play a useful role in the achievement of worthwhile goals beyond themselves, that NASA felt the need to grossly exaggerate their potential return as stand-alones. That pathology threatens to repeat itself.

We need to do better. Instead of organizing NASA’s activities around projects conceived largely to give the agency and its contractors something to do, and then justifying those programs with whatever excuses someone can dream up, NASA needs to set a rational objective for its human spaceflight program and devote its efforts and expenditures towards that end.

That goal can only be humans to Mars.

In contrast to a lunar return program supported by promises of electricity from moonbeams, human Mars exploration has a real rational purpose: the search to determine whether life is a general phenomenon in the universe and whether life as we know it on Earth is the pattern for all life everywhere, or whether we are just a particular example drawn from a much more diverse tapestry.

This is true, fundamental, science of a sort that bears on questions that thinking men and women have debated passionately for millennia. It is a goal that can be truthfully and forcefully defended as worth risking life and treasure for. It is a search that can only be accomplished by human explorers on Mars, because of the complexity of operations required to find, culture and characterize Martian life are far beyond the capacities of robotic devices.

Furthermore, since, unlike the carbon, nitrogen and water impoverished Moon, Mars possesses all the resources needed to support life and human settlement, if the objective of our space program is to extend human civilization into space, our goal needs to be to send humans to Mars. There is really no way around this.

There are legitimate reasons to send astronauts to the Moon, but just as was the case for the space station, these are in fact of insufficient worth to justify the huge cost and multi decade delay in the achievement of more important objectives that a stand-alone program must entail.

Therefore, since lunar activities can most rationally be supported as intermediate milestones in an effort to get humans to Mars, it should be clear that their hardware design requirements should be driven by the real goal. If we fail to take that approach, we will spend further tens of billions of dollars developing hardware, as exemplified by the shuttle and space station, that serves little useful purpose towards getting us where we want to go, and which will have to be set aside in order to accomplish anything real.

If we launch a lunar program with a hardware set designed for a Moon-only effort, the hardware will prove useless for Mars, and we will have to abandon the Moon while we spend many billions more and waste further decades to develop a second hardware set that can take us to the red planet. But if we intelligently design our hardware set for Mars, we can use a subset of that to reach the Moon.

By adopting such a rational approach, based upon real goals courageously embraced, NASA will be able to achieve truly valuable accomplishments with its manned spaceflight program, and do it at much lower cost, risk and time than would be possible otherwise.

It will cut cost because only one hardware set will need to be developed instead of two. It will cut schedule, radically, for the same reason. It will reduce risk because the lunar missions will be used to exercise the Mars flight hardware directly. It also will strengthen the rationale for the lunar program itself, because in this case it would really pave the way to Mars, and because, with a common hardware approach, the Moon would not have to be abandoned for the Mars program to begin.

However, if instead the agency allows itself to devolve into an irrational Moon-in-itself project, then it will end up repeating the wasteful folly of shuttle and the international space station , and create yet another tollbooth blocking America’s progress in space.

Upon that choice hangs the fate of the vision.

Dr. Robert Zubrin, an astronautical engineer, is president of the Mars Society ( and the author of The Case for Mars, Entering Space, and Mars on Earth.