by Michio Kaku
I got a personal look at this danger when I was a graduate student at the University of California at Berkeley. Moon rocks brought back from space in the early 1970s were creating a sensation in the scientific community. I was invited into a laboratory that was analyzing moon rock under a microscope. The rock I saw looked ordinary, since moon rock very closely resembles earth rock, but under the microscope I got quite a shock. I saw tiny meteor craters in the rock, and inside them I saw even tinier craters. Craters inside craters inside craters, something I had never seen before. I immediately realized that without an atmosphere, even the tiniest microscopic piece of dirt, hitting you at 40,000 miles per hour, could easily kill you or at least penetrate your space suit. (Scientists understand the enormous damage created by these micrometeorites because they can simulate these impacts, and they have created huge gun barrels in their labs that can fire metal pellets to study these meteor impacts.)
One possible solution is to build an underground lunar base. Because of the moon’s ancient volcanic activity, there is a chance our astronauts can find a lava tube that extends deep into the moon’s interior. (Lava tubes are created by ancient lava flows that have carved out cavelike structures and tunnels underground.) In 2009, astronomers found a lava tube about the size of a skyscraper that might serve as a permanent base on the moon.
This natural cave could provide cheap protection for our astronauts against radiation from cosmic rays and solar flares. Even taking a transcontinental flight from New York to Los Angeles exposes us to a millirem of radiation per hour (equivalent to getting a dental X-ray). For our astronauts on the moon, the radiation might be so intense that they might need to live in underground bases. Without an atmosphere, a deadly rain of solar flares and cosmic rays would pose an immediate risk to astronauts, causing premature aging and even cancer.
Weightlessness is also a problem, especially for long missions in space. I had a chance to visit the NASA training center in Cleveland, Ohio, where extensive tests are done on our astronauts. In one test I observed, the subject was suspended in a harness so that his body was parallel to the ground. Then he began to run on a treadmill, whose tracks were vertical. By running on this treadmill, NASA scientists could simulate weightlessness while testing the endurance of the subject.
When I spoke to the NASA doctors, I learned that weightlessness was more damaging than I had previously thought. One doctor explained to me that after several decades of subjecting American and Russian astronauts to prolonged weightlessness, scientists now realize that the body undergoes significant changes: degradation occurs in the muscles, bones, and cardiovascular system. Our bodies evolved over millions of years while living in the earth’s gravitational field. When placed in a weaker gravitational field for long periods of time, all our biological processes are thrown into disarray.
Russian astronauts who have spent about a year in space are so weak when they come back to earth that they can barely crawl. Even if they exercise daily in space, their muscles atrophy, their bones lose calcium, and their cardiovascular systems begin to weaken. Some of the astronauts take months to recover from this damage, some of which may be permanent. A trip to Mars, which might take two years, may drain the strength of our astronauts so they cannot perform their mission when they arrive. (One solution to this problem is to spin the spacecraft, which creates artificial gravity inside the ship. This is the same reason that you can spin a pail of water over your head without the water spilling out. But this is prohibitively expensive because of the heavy machinery necessary to spin the craft. Every pound of extra weight adds $10,000 to the cost of the mission.)
WATER ON THE MOON
One game changer has been the discovery of ancient ice on the moon, probably left over from ancient comet impacts. In 2009, NASA’s lunar crater observation and sensing satellite (LCROSS) probe and its Centaur booster rocket slammed into the moon’s south polar region. They hit the moon at 5,600 miles per hour, creating a plume almost a mile high, and a crater about 60 feet across. Although TV audiences were disappointed that the LCROSS impact did not create a spectacular explosion as predicted, it yielded a wealth of scientific data. About 24 gallons of water were found in that plume. Then, in 2010, scientists made the shocking announcement that 5 percent of the debris contained water, so the moon was actually wetter than parts of the Sahara desert.
This could be significant, because it might mean that future astronauts can harvest underground ice deposits for rocket fuel (by extracting the hydrogen in the water), for breathing (by extracting the oxygen), for shielding (since water can absorb radiation), and for drinking once it is purified. So this discovery could shave hundreds of millions of dollars off any mission to the moon.
This discovery may mean that it will be possible for our astronauts to live off the land, harvesting ice and minerals on the moon to create and supply a permanent base.
MISSION TO MARS
President Obama, when he journeyed to Florida in 2010 to announce the cancellation of the moon program, held out the prospects of a mission to Mars instead. He supported funding for a yet-unspecified heavy booster rocket that may one day send astronauts into deep space beyond the moon. He mused that he might see the day, perhaps in the mid-2030s, when our astronauts would walk on Mars. Some astronauts, like Buzz Aldrin, have been enthusiastic supporters of the Obama plan, because it would skip the moon. Aldrin once told me that the United States has already been to the moon, and hence the real adventure lies in going to Mars.
Of all the planets in the solar system, only Mars seems to resemble earth enough to harbor some form of life. (Mercury, which is scorched by the sun, is probably too hostile to have life as we know it. And the gas giants—Jupiter, Saturn, Uranus, and Neptune—are too cold to support life. Venus is a twin of the earth, but a runaway greenhouse effect has created a hellhole: temperatures soar to 900°F, its mostly carbon dioxide atmosphere is 100 times denser than ours, and it rains sulfuric acid. Walking on the Venusian surface, you would suffocate, be crushed to death, and your remains would be incinerated by the heat and dissolved by the sulfuric acid.)
Mars, on the other hand, was once a wet planet, like earth, with oceans and riverbeds that have long since vanished. Today, it is a frozen desert, devoid of life. Perhaps microbial life once flourished there billions of years ago or may still live underground in hot springs.
Once our nation has made a firm commitment to go to Mars, it may take another twenty to thirty years to actually complete the mission. But getting to Mars will be much more difficult than reaching the moon. In contrast to the moon, Mars represents a quantum leap in difficulty. It takes only three days to reach the moon. It takes six months to a year to reach Mars.
In July 2009, NASA scientists gave a rare look at what a realistic Mars mission might look like. Astronauts would take approximately six months or more to reach Mars, then spend eighteen months on the planet, then take another six months for the return voyage.
Altogether, about 1.5 million pounds of equipment would need to be sent to Mars, more than the amount needed for the $100 billion space station. To save on food and water, the astronauts would have to purify their own waste and then use it to fertilize plants during the trip and while on Mars. With no air, soil, or water, everything must be brought from earth. It will be impossible to live off the land, since there is no oxygen, liquid water, animals, or plants on Mars. The atmosphere is almost pure carbon dioxide, with an atmospheric pressure only 1 percent that of earth. Any rip in a space suit would create rapid depressurization and death.
The mission would be so complex that it would have to be broken down into several steps. Since carrying rocket fuel for the return mission back to earth would be costly, a separate rocket might be sent to Mars ahead of time carrying rocket fuel to be used for refueling the spacecraft. (Or, if enough oxygen and hydrogen could be extracted from the ice on Mars, this might be used for rocket fuel as well.)
Once on Mars, it might take weeks for the astronauts to get ac
customed to living on another planet. The day/night cycle is about the same as on earth (a day on Mars is 24.6 hours). But a year is almost twice as long. The temperature on Mars never goes above the melting point of ice. The dust storms on Mars are ferocious. The sand of Mars has the consistency of talcum powder, and dust storms that engulf the entire planet are common.
TERRAFORM MARS?
Assuming that astronauts visit Mars by midcentury and establish a primitive Martian outpost, there is the possibility that astronauts might consider terraforming Mars, that is, transforming the planet to make it more hospitable for life. This would begin late in the twenty-first century, at the earliest, or more likely early in the twenty-second.
Scientists have analyzed several ways in which Mars might be terraformed. Perhaps the simplest way would be to inject methane gas or other greenhouse gases into the atmosphere. Since methane gas is an even more potent greenhouse gas than carbon dioxide, the methane gas might be able to trap sunlight, raising the surface temperature of Mars to above the melting point of ice. In addition to methane, other greenhouse gases have been analyzed for possible terraforming experiments, such as ammonia and chlorofluorocarbons.
Once the temperature starts to rise, the underground permafrost may begin to thaw out, for the first time in billions of years. As the permafrost melts, riverbeds would begin to fill up with water. Eventually, lakes and even oceans might form again on Mars as the atmosphere thickens. This would release more carbon dioxide, setting off a positive feedback loop.
In 2009 it was discovered that methane gas naturally escapes from the Martian surface. The source of this gas is still a mystery. On earth, most of the methane gas is due to the decay of organic materials. But on Mars, the methane gas may be a by-product of geologic processes. If one can locate the source of this methane gas, then it might be possible to increase its output and hence alter the atmosphere.
Another possibility is to deflect a comet into the Martian atmosphere. If one can intercept a comet far enough away, then even a small nudge by a rocket engine, an impact with a probe, or even the tug of the gravity of a spaceship might be enough to deflect it. Comets are made mainly of water ice and periodically race through our solar system. (Halley’s comet, for example, consists of a core—resembling a peanut—that is roughly twenty miles across, made mainly of ice and rock.) As the comet gradually gets closer to the surface of Mars, it would encounter friction from the atmosphere, causing the comet to slowly disintegrate, releasing water into the atmosphere in the form of steam.
If comets are not available, it could also be possible to deflect one of the ice moons of Jupiter or perhaps an asteroid that contains ice, such as Ceres, which is believed to be 20 percent water. (These moons and asteroids would be harder to deflect, since they are usually in stable orbits.) Instead of having the comet, moon, or asteroid slowly decay in its orbit around Mars, releasing water vapor, another choice would be to maneuver them into a controlled impact on the Martian ice caps. The polar regions of Mars are made of frozen carbon dioxide, which disappears during the summer months, and ice, which makes up the permanent part of the ice caps. If the comet, moon, or asteroid hits the ice caps, they can release a tremendous amount of heat and vaporize the dry ice. Since carbon dioxide is a greenhouse gas, this would thicken the atmosphere and help to accelerate global warming on Mars. It might also create a positive feedback loop. The more carbon dioxide is released from the ice caps, the warmer the planet becomes, which in turn releases even more carbon dioxide.
Another suggestion is to detonate nuclear bombs directly on the ice caps. The drawback is that the resulting liquid water might contain radioactive fallout. Or we could try to create a fusion reactor that can melt the polar ice caps. Fusion plants use water as a basic fuel, and there is plenty of frozen water on Mars.
Once the temperature of Mars rises to the melting point of ice, pools of water may form, and certain forms of algae that thrive on earth in the Antarctic may be introduced to Mars. They might actually thrive in the atmosphere of Mars, which is 95 percent carbon dioxide. They could also be genetically modified to maximize their growth on Mars. These algae pools could accelerate terraforming in several ways. First, they could convert carbon dioxide into oxygen. Second, they would darken the surface color of Mars, so that it absorbs more heat from the sun. Third, since they grow by themselves without any prompting from the outside, it would be a relatively cheap way to change the environment of the planet. Fourth, the algae can be harvested for food. Eventually these algae lakes would create soil and nutrients that may be suitable for plants, which in turn would accelerate the production of oxygen.
Scientists have also looked into the possibility of building solar satellites surrounding the planet, reflecting sunlight onto Mars. Solar satellites by themselves might be able to heat the Martian surface above freezing. Once this happens and the permafrost begins to melt, the planet would naturally continue to warm on its own.
ECONOMIC BENEFIT?
One should have no illusions that we will benefit immediately from an economic bonanza by colonizing the moon and Mars. When Columbus sailed to the New World in 1492, he opened the door to a historic economic windfall. Soon, the conquistadors were sending back huge quantities of gold that they plundered from Native Americans, and settlers were sending valuable raw materials and crops back to the Old World. The cost of sending expeditions to the New World was more than offset by the fabulous fortunes that could be made.
But colonies on the moon or Mars are quite different. There is no air, liquid water, or fertile soil, so everything would have to be brought by rocket ship, which is prohibitively expensive.
Furthermore, there is little military value to colonizing the moon, at least for the near term. This is because it takes three days on average to reach the moon from the earth or vice versa, but a nuclear war can be fought in just ninety minutes by intercontinental ballistic missiles. A space cavalry on the moon would not reach the battle on earth in time to make a difference. Hence, the Pentagon has not funded any crash program to weaponize the moon.
This means that if we do initiate large-scale mining operations on other worlds, it will be for the benefit of space colonies, not for the earth. Colonists will extract the metals and minerals for their own use, since it would cost too much to transport them to earth. Mining operations in the asteroid belt would become economic only when we have self-sustaining colonies that can use these raw materials themselves, which won’t happen until late in this century or, more likely, beyond.
SPACE TOURISM
But when might the average civilian go into space? Some visionaries, like the late Gerard O’Neill of Princeton University, dreamed of a space colony as a gigantic wheel, including living units, water-purification plants, air-recycling units, etc., established to solve overpopulation on earth. But in the twenty-first century, the idea that space colonies would relieve the population problem is fanciful at best. For the majority of the human race, earth will be our only home for at least a century or more.
However, there is one way in which the average person may realistically go into space: as a tourist. Some entrepreneurs, who criticize the enormous waste and bureaucracy of NASA, think they can drive down the cost of space travel using market forces. Already, Burt Rutan and his investors won the $10 million Ansari X Prize on October 4, 2004, by having launched SpaceShipOne twice within two weeks to just over 62 miles above the earth. SpaceShipOne is the first rocket-powered spacecraft to have successfully completed a privately funded venture into space. Development costs were about $25 million. Microsoft billionaire Paul Allen helped to underwrite the project.
Now, with SpaceShipTwo, Rutan expects to begin tests to make commercial spaceflight a reality. Billionaire Richard Branson of Virgin Atlantic has created Virgin Galactic, with a spaceport in New Mexico and a long list of people who will spend $200,000 to realize their dream of flying into space. Virgin Galactic, which will be the first major company to offer commercial flights into spa
ce, has already ordered five SpaceShipTwo rockets. If successful, this might drive down the cost of space travel by a factor of ten.
SpaceShipTwo uses several methods to cut costs. Instead of huge booster rockets to carry the payload into space, Rutan places his spaceship atop an airplane, so that it can piggyback on a standard air-breathing plane. This way, you simply consume the oxygen in the atmosphere to reach high altitudes. Then, at about 10 miles above the earth, the spaceship separates from the airplane and turns on its rocket engines. Although the spaceship cannot orbit the earth, it has enough fuel to reach almost 70 miles above the earth, above most of the atmosphere, so passengers can see the sky turn purple and then black. Its engines are powerful enough to hit Mach 3, or three times the speed of sound (roughly 2,200 miles per hour). This is certainly not fast enough to put a rocket into orbit (you need to hit 18,000 miles per hour for that), but it is enough to take you to the edge of the atmosphere and the threshold of outer space. In the near future, perhaps a trip to space may cost no more than a safari in Africa.
(However, to go completely around the earth, you would need to pay considerably more to take a trip aboard the space station. I once asked Microsoft billionaire Charles Simonyi how much it cost him to get a ticket to the Space Station. Media reports estimated that it cost $20 million. He said he was reluctant to give the precise cost, but he told me that the media reports were not far off. He had such a good time that he actually went into space twice. So space travel, even into the near future, will still be the province of the well-off.)
Space tourism, however, got a shot in the arm in September 2010, when the Boeing Corporation announced that it, too, was entering the business, with commercial flights for tourists planned as early as 2015. This would bolster President Obama’s decision to turn over the manned spaceflight program to private industry. Boeing’s plan calls for launches to the International Space Station from Cape Canaveral, Florida, each involving four crew members, which would leave free up to three seats for space tourists. Boeing, however, was blunt about the financing for private ventures into space: the taxpayer would have to pay most of the bill. “This is an uncertain market,” says John Elbon, program manager for Boeing’s commerical crew effort. “If we had to do this with Boeing investment only and the risk factors were in there, we wouldn’t be able to close the business case.”
