ll exact copies of what's on Mars； and all experienced from the safety of a virtual reality salon in your hometown。 This is not why we explore Mars； but clearly we will need robot explorers to return the real reality before it can be reconfigured into virtual reality。
Especially with continuing investment in robotics and machine intelligence； sending humans to Mars can't be justified by science alone。 And many more people can experience the virtual Mars than could possibly be sent to the real one。 We can do very well with robots。 If we're going to send people； we'll need a better reason than science and exploration。
In the 1980s； I thought I saw a coherent justification for human missions to Mars。 I imagined the United States and the Soviet Union； the two Cold War rivals that had put our global civilization at risk； joining together in a far…seeing； high…technology endeavor that would give hope to people everywhere。 I pictured a kind of Apollo program in reverse； in which cooperation； not petition； was the driving force； in which tire two leading space…faring nations would together lay the groundwork for a major advance in human history—the eventual settlement of another planet。
The symbolism seemed so apt。 The same technology that can propel apocalyptic weapons from continent to continent would enable the first human voyage to another planet。 It was a choice of fitting mythic power： to embrace the planet named after； rather the madness ascribed to； the god of war。
We succeeded in interesting Soviet scientists and engineers in such a joint endeavor。 Roald Sagdeev； then director of the Institute for Space Research of the Soviet Academy of Sciences in Moscow； was already deeply engaged in international cooperation on Soviet robotic missions to Venus； Mars； and Halley's et； long before the idea became fashionable。 Projected joint use of the Soviet Mir space station and the Saturn V…class launch vehicle Energiya made cooperation attractive to the Soviet organizations that manufactured these items of hardware； they were otherwise having difficulty justifying their wares。 Through a sequence of arguments （helping to bring the Cold War to an end being chief among them）； then…Soviet leader Mikhail S。 Gorbachev was convinced。 During the December 1987 Washington summit； Mr。 Gorbachev—asked what was the most important joint activity through which the two countries might symbolize the change in their relationship—unhesitatingly replied； 〃Let's go to Mars together。〃
But the Reagan Administration was not interested。 Cooperating with the Soviets； acknowledging that certain Soviet technologies were more advanced than their American counterparts； making some American technology available to the Soviets； sharing credit； providing an alternative for the arms manufacturers—these were not to the Administration's liking。 The offer was turned down。 Mars would have to wait。
In only a few years； times have changed。 The Cold War is over。 The Soviet Union is no more。 The benefit deriving from the two nations working together has lost some of its force。 Other nations—especially Japan and the constituent members of the European Space Agency—have bee interplanetary travelers。 Many just and urgent demands are levied on the discretionary budgets of the nations。
But the Energiya heavy…lift booster still awaits a mission。 The workhorse Proton rocket is available。 The Mir space station—with a crew on board almost continuously—still orbits the Earth every hour and a half。 Despite internal turmoil； the Russian space program continues vigorously。 Cooperation between Russia and America in space is accelerating。 A Russian cosmonaut； Sergei Krikalev； in 1994 flew on the shuttle Discovery （for the usual one…week shuttle mission duration； Krikalev had already logged 464 days aboard the Mir space station）。 U。S。 astronauts will visit Mir。 American instruments—including one to examine the oxidants thought to destroy organic molecules in the Martian soil—are to be carried by Russian space vehicles to Mars。 Mars Observer was designed to serve as a relay station for landers in Russian Mars missions。 The Russians have offered to include a U。S。 orbiter in a forthing Proton…launched multipayload mission to Mars。
The American and Russian capabilities in space science and technology mesh； they interdigitate。 Each is strong where the other is weak。 This is a marriage made in heaven…but one that has been surprisingly difficult to consummate。
On September 2； 1993； an agreement to cooperate in depth was signed in Washington by Vice President Al Gore and Prime Minister Viktor Chernomyrdin。 The Clinton Administration has ordered NASA to redesign the U。S。 space station （called Freedom in the Reagan years） so it is in the same orbit as Mir and can be mated to it： Japanese and European modules will be attached； as will a Canadian robot arm。 The designs have now evolved into what is called Space Station Alpha； involving almost all the spacefaring nations。 （China is the most notable exception。）
In return for U。S。 space cooperation and an infusion of hard currency； Russia in effect agreed to halt its sale of ballistic missile ponents to other nations； and generally to exercise tight controls on its export of strategic weapons technology。 In this Way； space bees once again； as it was at the height of the Cold War； an instrument of national strategic policy。
This new trend has； though； made some of the American aerospace industry and some key members of Congress profoundly uneasy。 Without international petition； can we motivate such ambitious efforts？ Does every Russian launch vehicle used cooperatively mean less support for the American aerospace industry？ Can Americans rely on stable support and continuity of effort in joint projects with the Russians？ （The Russians； of course； ask similar questions about the Americans。） But cooperative programs in the long term save money； draw upon the extraordinary scientific and engineering talent distributed over our planet； and provide inspiration about the global future。 There may be fluctuations in national mitments。 We are likely to take backward as well as forward steps。 But the overall trend seems clear。
Despite growing pains； the space programs of the two former adversaries are beginning to join。 It is now possible to foresee a world space station—not of any one nation but of the planet Earth—being assembled at 51° inclination to the equator and a few hundred miles up。 A dramatic joint mission； called 〃Fire and Ice；〃 is being discussed in which a fast flyby would be sent to Pluto； the last unexplored planet； but to get there； a gravity assist from the Sun would be employed； in the course of Which small probes would actually enter the Sun's atmosphere。 And we seem to be on the threshold of a World Consortium for the scientific exploration of Mars。 It very much looks as though such projects will be done cooperatively or not at all。
WHETHER THERE ARE VALID； cost…effective； broadly supportable reasons for people to venture to Mars is an open question。 Certainly there is no consensus。 The matter is treated in the next chapter。
I would argue that if we are not eventually going to send people to worlds as far away as Mars； we have lost the chief reason for a space station—a permanently （or intermittently） occupied human outpost in Earth orbit。 A space station is far from an optimum platform for doing science either looking down at the Earth； or looking out into space； or for utilizing microgravity （the very presence of astronauts messes things up）。 For military reconnaissance it is much inferior to robotic spacecraft。 There are no pelling economic or manufacturing applications。 It is expensive pared to robotic spacecraft。 And of course it runs some risk of losing human lives。 Every shuttle launch to help build or supply a space station has an estimated 1 or 2 percent chance of catastrophic failure。 Previous civilian and military space activities have littered low Earth orbit with fast…moving debris—that sooner or later will collide with a space station （although； so far； Mir has had no failures from this hazard）。 A space station is also unnecessary for human exploration of the Moon。 Apollo got there very well with no space station at all。 With Saturn V or Energiya class launchers； it also may be possible to get to near…earth asteroids or even Mars without having to assemble the interplanetary vehicle on an orbiting space station。
A space station could serve inspirational and educational purposes； and it certainly can help to solidify relations among the spacefaring nations—particularly the United States and Russia。 But the only substantive function of a space station； as far as I can see； is for long…duration spaceflight。 How do humans behave in micro gravity？ How can we counter progressive changes in blood chemistry and an estimated 6 percent bone loss per year in zero gravity？ （For a three… or four…year mission to Mars this adds up； if the travelers have to go at zero g。）
These are hardly questions in fundamental biology such as DNA or the evolutionary process； instead they address issues of applied human biology。 It's important to know the answers； but only if we intend to go somewhere in space that's far away and takes a long time to get there。 The only tangible and coherent goal of a space station is eventual human missions to near…Earth asteroids； Mars； and beyond。 Historically NASA has been cautious about stating this fact clearly； probably for fear that members of Congress will throw up their hands in disgust； denounce the space station as the thin edge of an extremely expensive wedge； and declare the country unready to mit to launching people to Mars。 In effect； then； NASA has kept quiet about what the space station is really for。 And yet if we had such a space station； nothing would require us to go straight to Mars。 We could use a space station to accumulate and refine the relevant knowledge； and take as long as we like to do so—so that when the time does e； when we are ready to go to the planets； we will have the background and experience to do so safely。
The Mars Observer failure； and the catastrophic loss of the space shuttle Challenger in 1986； remind us that there will be a certain irreducible chance of disaster in future human flights to Mars and elsewhere。 The Apollo 13 mission； which was unable to land on the Moon and barely returned safely to Earth； underscores how lucky we've been。 We cannot make perfectly safe autos or trains even though we've been at it for more than a century。 Hundreds of thousands of years after we first domesticated fire； every city in the world has a service of firefighters biding their time until there's a blaze that needs putting out。 In Columbus' four voyages to the New World； he lost ships left and right； including one third of the little fleet that set out in 1492。
If we are to send people； it must be for a very good reason—and with a realistic understanding that almost certainly we will lose lives。 Astronauts and cosmonauts have always understood this。 Nevertheless； there has been and will be no shortage of volunteers。
But why Mars？ Why not return to the Moon？ It's nearby； and we've proved we know how to send people there。 I'm concerned that the M