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be clever about reducing costs and making true international partnerships； the justifications bee more pelling。
Until a national debate on this topic has transpired； until we have a better idea of the rationale and the cost/benefit ratio of human missions to Mars； what should we do？ My suggestion is that we pursue research and development projects that can be justified on their own merits or by their relevance to other goals； but that can also contribute to human missions to Mars should we later decide to go。 Such an agenda would include：
·U。S。 astronauts on the Russian space station Mir for joint flights of gradually increasing duration； aiming at one to two years； the Mars flight time。
·Configuration of the international space station so its principal function is to study the long…term effects of the space environment on humans。
·Early implementation of a rotating or tethered 〃artificial gravity〃 module on the international space station； for other animals and then for humans。
·Enhanced studies of the Sun； including a distributed set of robot probes in orbit about the Sun； to monitor solar activity and give the earliest possible warning to astronauts of hazardous 〃solar flares〃—mass ejections of electrons and protons from the Sun's corona。
·U。S。/Russian and multilateral development of Energiya and Proton rocket technology for the U。S。 and international space programs。 Although the United States is unlikely to depend primarily on a Soviet booster； Energiya has roughly the lift of the Saturn V that sent the Apollo astronauts to the Moon。 The United States let the Saturn V assembly line die； and it cannot readily be resuscitated。 Proton is the most reliable large booster now in service。 Russia is eager to sell this technology for hard currency。
·Joint projects with NASDA （the Japanese space agency） and Tokyo University； the European Space Agency； and the Russian Space Agency； along with Canada and other nations。 In most cases these should be equal partnerships； not the United States insisting on calling the shots。 For the robotic exploration of Mars； such programs are already under way。 For human flight； the chief such activity is clearly the international space station。 Eventually； we might muster joint simulated planetary missions in low Earth orbit。 One of the principal objectives of these programs should be to build a tradition of cooperative technical excellence。
·Technological development—using state…of…the…art robotics and artificial intelligence—of rovers； balloons； and aircraft for the exploration of Mars； and implementation of the first international return sample mission。 Robotic spacecraft that can return samples from Mars can be tested on near…Earth asteroids and the Moon。 Samples returned from carefully selected regions of the Moon can have their ages determined and contribute in a fundamental way to our understanding of the early history of the Earth。
·Further development of technologies to manufacture fuel and oxidizer out of Martian materials。 In one estimate； based on a prototype instrument designed by Robert Zubrin and colleagues at the Martin Marietta Corporation； several kilograms of Martian soil can be automatically returned to Earth using a modest and reliable Delta launch vehicle； all for no more than a song （paratively speaking）。
·Simulations on Earth of long…duration trips to Mars； concentrating on potential social and psychological problems。
·Vigorous pursuit of new technologies such as constant…thrust propulsion to get us to Mars quickly； this may be essential if the radiation or microgravity hazards make one…year （or longer） flight times too risky。
·Intensive study of near…Earth asteroids； which may provide superior intermediate…timescale objectives for human exploration than does the Moon。
·A greater emphasis on science—including the fundamental sciences behind space exploration； and the thorough analysis of data already obtained—by NASA and other space agencies。
These remendations add up to a fraction of the full cost of a human mission to Mars and—spread out over a decade or so and done jointly with other nations—a fraction of current space budgets。 But； if implemented； they would help us to make accurate cost estimates and better assessment of the dangers and benefits。 They would permit us to maintain vigorous progress toward human expeditions to Mars without premature mitment to any specific mission hardware。 Most； perhaps all； of these remendations have other justifications； even if We were sure wed be unable to send humans to any other world in the next few decades。 And a steady drumbeat of acplishments increasing the feasibility of human voyages to Mars would—in the minds of many at least—bat widespread pessimism about the future。
THERE'S SOMETHING MORE。 There's a set of less tangible arguments； many of which； I freely admit； I find attractive and resonant。 Spaceflight speaks to something deep inside us—many of us； if not all。 An emerging cosmic perspective； an improved understanding of our place in the Universe； a highly visible program affecting our view of ourselves might clarify the fragility of our planetary environment and the mon peril and responsibility of all the nations and peoples of Earth。 And human missions to Mars would provide hopeful prospects； rich in adventure； for the wanderers among us； especially the young。 Even vicarious exploration has social utility。
I repeatedly find that when I give talks on the future of the space program—to universities； business and military groups； professional organizations—the audiences are much less patient with practical； real…world political and economic obstacles than 1。 They long to sweep away the impediments； to recapture the glory days of Vostok and Apollo； to get on with it and once more tread other worlds。 We did it before； we can do it again； they say。 But； I caution myself； those who attend such talks are self…selected space enthusiasts。
In 1969； less than half the American people thought the Apollo program was worth the cost。 But on the twenty…fifth anniversary of the Moon landing； the number had risen to two thirds。 Despite its problems； NASA was rated