But whether in single launches or in pairs, the space-faring nations have clearly decided that the time is ripe to return robot explorers to Mars. Mission designs change; new nations enter the field; old nations find they no longer have the resources. Even already funded programs cannot always be relied upon. But current plans do reveal something of the intensity of effort and the depth of dedication.
As I write this book, there are tentative plans by the United States, Russia, France, Germany, Japan, Austria, Finland, Italy, Canada, the European Space Agency, and other entities for a coordinated robotic exploration of Mars. In the seven years between 1996 and 2003, a flotilla of some twenty-five spacecraft—most of them comparatively small and cheap—are to be sent from Earth to Mars. There will be no quick flybys among them; these are all long-duration orbiter and lander missions. The United States will re-fly all of the scientific instruments that were lost on Mars Observer. The Russian spacecraft will contain particularly ambitious experiments involving some twenty nations. Communications satellites will permit experimental stations anywhere on Mars to relay their data back to Earth. Penetrators screeching down from orbit will punch into the Martian soil, transmitting data from underground. Instrumented balloons and roving laboratories will wander over the sands of Mars. Some microrobots will weigh no more than a few pounds. Landing sites are being planned and coordinated. Instruments will be cross-calibrated. Data will be freely exchanged. There is every reason to think that in the coming years Mars and its mysteries will become increasingly familiar to the inhabitants of the planet Earth.
IN THE COMMAND CENTER on Earth, in a special room, you are helmeted and gloved. You turn your head to the left, and the cameras on the Mars robot rover turn to the left. You see, in very high definition and in color, what the cameras see. You take a step forward, and the rover walks forward. You reach out your arm to pick up something shiny in the soil, and the robot arm does likewise. The sands of Mars trickle through your fingers. The only difficulty with this remote reality technology is that all this must occur in tedious slow motion: The round-trip travel time of the up-link commands from Earth to Mars and the down-link data returned from Mars to Earth might take half an hour or more. But this is something we can learn to do. We can learn to contain our exploratory impatience if that's the price of exploring Mars. The rover can be made smart enough to deal with routine contingencies. Anything more challenging, and it makes a dead stop, puts itself into a safeguard mode, and radios for a very patient human controller to take over.
Conjure up roving, smart robots, each of them a small scientific laboratory, landing in the safe but dull places and wandering to view close-up some of that profusion of Martian Wonders. Perhaps every day a robot would rove to its own horizon; each morning we would see close-up what had yesterday been only a distant eminence. The lengthening progress of a traverse route over the Martian landscape would appear oil news programs and in schoolrooms. People would speculate on what will be found. Nightly newscasts from another planet, with their revelations of new terrains and new scientific findings would make everyone on Earth a party to the adventure.
Then there's Martian virtual reality: The data sent back from Mars, stored in a modern computer, are fed into your helmet and gloves and boots. You are walking in an empty room on Earth, but to you you are on Mars: pink skies, fields of boulders, sand dunes stretching to the horizon where an immense volcano looms; you hear the sand crunching under your boots, you turn rocks over, dig a hole, sample the thin air, turn a corner, and come face to face with . . . whatever new discoveries we will make on Mars—all 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 competition, 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 Comet, 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 become 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 forthcoming 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 components to other nations, and generally to exercise tight controls on its export of strategic weapons technology. In this Way, space becomes 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 competition, 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 commitments. 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 compelling economic or manufacturing applications. It is expensive compared 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 commit 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 come, 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 Moon, close as it is, is a long detour, if not a dead end. We've been there. We've even brought some of it back. People have seen the Moon rocks, and, for reasons that I believe are fundamentally sound, they are bored by the Moon. It's a static, airless, waterless, black-sky, dead world. Its most interesting aspect perhaps is its cratered surface, a record of ancient ,catastrophic impacts, on the Earth as well as on the Moon.
Mars, by contrast, has weather, dust storms, its own moons, volcanos, polar ice caps, peculiar landforms, ancient river valleys, and evidence of massive climatic change on a once-Earthlike world. It holds some prospect of past or maybe even present life, and is the most congenial planet for future life—humans transplanted from Earth, living off the land. None of this is true for the Moon. Mars also has its own legible cratering history. It Mars, rather than the Moon, had been within easy reach, we would not have backed off from manned space flight.
Nor is the Moon an especially desirable test bed or way station for Mars. The Martian and lunar environments are very different, and the Moon is as distant from Mars as is the Earth. The machinery for Martian exploration can at least equally well be tested in Earth orbit, or on near-Earth asteroids, or on the Earth itself—in Antarctica, for instance.
Japan has tended to be skeptical of the commitment of the United States and other nations to plan and execute major cooperative projects in space. This is at least one reason that Japan, more than any other spacefaring nation, has tended to go it alone. The Lunar and Planetary Society of Japan is an organization representing space enthusiasts in the government, universities, and major industries. As I write, the Society is proposing to construct and stock a lunar base entirely with robot labor. It is said to take about 30 years and to cost about a billion U.S. dollars a year (which would represent 7 percent of the present U.S. civilian space budget). Humans would arrive only when the base is fully ready. The use of robot construction crews under radio command from Earth is said to reduce the cost tenfold. The only trouble with th
e scheme, according to reports, is that other scientists in Japan keep asking, "What's it for?" That's a good question in every nation.
The first human mission to Mars is now probably too expensive for any one nation to pull off by itself. Nor is it fitting that such a historic step be taken by representatives of only a small fraction of the human species. But a cooperative venture among the United States, Russia, Japan, the European Space Agency—and perhaps other nations, such as China—might be feasible in the not too distant future. The international space station will have tested our ability to work together on great engineering projects in space.
The cost of sending a kilogram of something no farther away than low Earth orbit is today about the same as the cost of kilogram of gold. This is surely a major reason we have yet to stride the ancient shorelines of Mars. Multistage chemical rockets are the means that first took us into space, and that's what we've been using ever since. We've tried to refine them, to make there safer, more reliable, simpler, cheaper. But that hasn't happened, or at least not nearly as quickly as many had hoped.
So maybe there's a better way: maybe single-stage rockets that can launch their payloads directly to orbit; maybe many small payloads shot from guns or rocket-launched from airplanes; maybe supersonic ramjets. Maybe there's something much better that we haven't thought of yet. If we can manufacture propellants for the return trip from the air and soil of our destination world, the difficulty of the voyage would be greatly eased.
Once we're up there in space, venturing to the planets, rocketry is not necessarily the best means to move large payloads around, even with gravity assists. Today, we make a few early rocket burns and later midcourse corrections, and coast the rest of the way. But there are promising ion and nuclear/ electric propulsion systems by which a small and steady acceleration is exerted. Or, as the Russian space pioneer Konstantin Tsiolkovsky first envisioned, we could employ solar sails—vast but very thin films that catch sunlight and the solar wind, a caravel kilometers wide plying the void between the worlds. Especially for trips to Mars and beyond, such methods are far better than rockets.