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Mars exploration illustration
Humans, augmented with robot helpers, may be the most efficient wqay to explore Mars. (credit: NASA)

Giving future human space explorers the credit they’re due

The debate surrounding the value of human versus robotic exploration has largely ignored the fact that humans are vastly more capable of exploring planetary surfaces than are robotic rovers. Indeed, Mars-analog exploration conducted by the Mars Society suggests that humans can do “rover science” thousands of times faster than rovers. Rovers are incapable of conducting even a small fraction of the science humans are capable of, including the most important Martian science objectives: detailing its geologic history and searching for fossil or living organisms. If current thinking prevails, it will be in vain pursuit of these two objectives that billions more will be spent on increasingly expensive rovers, while a single human mission could be conducted more quickly, with greater likelihood of mission success, and even at lower cost.

Of all possible targets for inner solar system exploration, Mars exploration is the most attractive because it offers both important science objectives and broad public enthusiasm. Though per-haps not strictly necessary, as a variety of big science and engineering projects (such as the CERN particle accelerator and the ITER fusion project) demonstrate, broad public enthusiasm is absolutely vital in maintaining the budget of a decadal-long space exploration program. Mars is the closest planetary body that is both capable of being immediately explored and potentially ca-pable of harboring life, making its exploration one of the most exciting scientific, engineering, and societal challenges facing the world today. Thus, any chosen surface exploration regime, be it robotic, human, or both, should be the one that provides the capability to succeed as quickly, and cheaply, as possible.

Yet, for a almost billion dollars, not much science has been returned; it is only through the reduced expectations of rover science that an average speed of 3.2 kilometers per year could be considered an unqualified success.

Manned exploration critics have pointed to the Mars Exploration Rovers (MERs), Spirit and Op-portunity, as final proof of the obsolescence of humans; but as the mission’s science director Steve Squyers attests, they are a poor substitute. The MERs landed on Mars in January and Feb-ruary of 2004, since having traveled a combined total of approximately 11 kilometers. Along the way they snapped tens of thousands of photographs, gathered hundreds of reflected energy spectra of rocks and soil, and provided megabytes of other data. By most measures, they have succeeded tremendously, and, due largely to the extreme fortuity of the “hole-in-one” landing of Opportunity in Eagle Crater, they found evidence for the past activity of water on Mars within their 90-day primary science mission. Since those auspicious beginnings they have kept on rolling, and thanks to helpful Martian winds appear nearly as healthy now as when they landed.

Yet, for a almost billion dollars, not much science has been returned; it is only through the reduced expectations of rover science that an average speed of 3.2 kilometers per year could be considered an unqualified success. Hundreds of Earth-based researchers have devoted years of their careers to studying the relatively few relevant pictures and energy spectra that the rovers have managed to return, all the while frustrated by their inability to truly collect all of the data they need. Researchers cling to tenuously thin lines of reasoning while making pronouncements that Mars was once wet, but because of the rovers’ glacial pace of exploration additional evidence awaits future rover programs. Moreover, because of their extremely limited capacity, the MERs addressed few, if any, of the most pressing scientific questions related to Mars. They answered only the very tiny sub-question: “is there some evidence of the past activity of water in two small areas of Mars?”

Because NASA had been either unwilling or unable to promote human exploration of Mars, pri-vate groups such as the Mars Society stepped in to fill the void. Since humans have never explored at length the surface of a body that lacks the atmosphere we need to breath, we do not know how capable we are of such a task. To help rectify this, the Mars Society began a program of exploration simulation at Devon Island in Canada in 2000. Their Flashline Mars Arctic Re-search Station (FMARS) has been crewed each summer since. A second station in the Utah de-sert near Hanksville was constructed a year later, and a third is awaiting deployment in Iceland during the summer of 2006. Their Mars-analog suits simulate true spacesuits in weight, visibil-ity, endurance, and mobility constraints, while the station and its operational rules simulate the constraints of a pressurized atmosphere that a true Mars habitat would impose. Working under this broad framework of simulation, hundreds of scientists and engineers have conducted mis-sions of exploration, science, and engineering, recording and reporting their experiences and re-sults. During the summer of 2005, I spent three weeks at FMARS as the crew’s hydrologist and engineer. I designed my exploration program around understanding the local mud phenomenon that is potentially an analog to some types of Martian dust, characterizing the stations’ water supply, and comparing the performance of an in-simulation crew to the Mars Exploration Rovers (MERs) Spirit and Opportunity.

The surface of Devon Island near FMARS is boulder-strewn and hilly. Its terrain would be exactly the place that landing site selection committees would avoid, because there a wheeled rover might not even get to leave its landing platform, assuming it could land safely at all. But humans can explore such an area quite easily. Steep talus-slope hills are no real problem for pe-destrian humans to traverse, and even over this terrain explorers are capable of averaging 1 km/hr with lengthy stops to conduct imaging and investigate the biology, paleontology, and rock and soil compositions of at least one site each hour. At this rate, humans can traverse the Martian terrain in scientific exploration mode more than two thousand times faster than the MERs. Ad-ditionally, humans can conduct a more detailed investigation of important rocks and outcrops using the same instruments as the MERs in a tiny fraction of the time that they would require. But even these criticisms have given robotic craft far more credit than they merit when compared to human explorers. No rover that could be built in the next few decades would be capable of excavating a partially buried rock, drilling hundreds of meters to find liquid water, repairing bro-ken parts, creating new tools not foreseen by mission planners, or visiting the thousands of sites necessary to seriously look for fossil or living biology.

By extension of the analog simulation results at FMARS, the short-term science objectives of all of the Mars landers and rovers thus far could be accomplished within a few weeks of landing by a six-person crew.

Rovers do seem to have the advantage of costing significantly less than a human program. But, if the ultimate aim of the program is answering the geologic and biologic questions surrounding Mars rovers will cost more than human exploration. To date, NASA’s surface exploration of Mars has cost much less than the estimated $50–100 billion price tag for a first manned Mars mission (forecasting cost is notoriously difficult, but the exact number does not alter the argu-ment in this case). Indeed, in 2003 dollars, the total cost of all NASA-led surface-landing Mars missions to date is somewhere near $4.2 billion. But despite having spent nearly one tenth to one twentieth the cost of a human Mars mission on landers and rovers, we have returned nowhere near one tenth to one twentieth the science of a manned mission. By extension of the analog simulation results at FMARS, the short-term science objectives of all of the Mars landers and rovers thus far could be accomplished within a few weeks of landing by a six-person crew. During the remainder of their approximately 500 days on the surface, the crew could accomplish (in terms of deliverables to Mission Control) more than a hundred times the total science return of all previous rovers and landers, including a serious geologic survey and search for life that no robotic mission could conduct.

There remains one significant criticism of manned exploration, for as we have seen with the editorial response to the loss of Columbia in 2003, the perceived risk of a human exploration program is too great for many critics. It is impossible to say what the true risk of a manned Mars program might be, but consider an anecdote that suggests the risk to taxpayers’ money of manned mission failure may be significantly lower than that of robotic missions: the twin failures of the Mars Climate Orbiter (MCO) and the Mars Polar Lander (MPL) in 1999. MCO failed due to an incorrect assumption of the unit of force in data provided to NASA by Lockheed Martin, while MPL probably failed because of spurious data that resulted in premature engine shutdown. Both of these problems would very likely not have been fatal to a manned crew, as the pilots would have stepped in and taken control when problems were detected. There remains significant risk from the environment both in space and on Mars, but these are manageable risks as well. Health risks are unavoidable, but most of the likely problems would not be mission-ending. Additionally, risk of equipment failure is much higher on the more complicated manned missions. But, unlike getting rovers to succeed in real Mars exploration, mission success is largely a problem of engineering, not a lack of technology. And such is the human exploring spirit that whatever the true risks, many will accept them gladly; the pool of willing and qualified “Marsnaut” candidates will be enormous.

Savvy writers have long recognized that the true debate is not humans vs. robots, yet prominent “either/or” critics continue to draw attention in the media. Mars analog simulation suggests that human explorers, supplemented by orbital probes and specialty robotic helpers, can accomplish the scientific exploration of Mars in a fraction of the time and at lower cost than an all-robotic program. Human explorers would also bring a cultural and educational importance to the mission that no robotic craft, even the venerable Hubble Space Telescope, can boast. Most importantly, unlike rovers, humans are capable of seriously attempting to answer one of the most important scientific and philosophical questions facing society today: “are we alone?” Perhaps in many decades robots will achieve this capability, but only if we continue to pour billions into their comparatively limited programs. And as every mission failure increases the risk of program cancellation, a fully-robotic Mars exploration program may be canceled long before the necessary capability is reached. If we want to learn if Mars harbors fossil or living organisms and uncover its geologic history, we will need to send humans. Otherwise, in the end, we will have spent much more, learned less, and gone without the heart and soul of exploration: human triumph.