Beyond: Our Future in Space (23 page)

Mars is a challenging goal for human exploration. The problem isn’t energy. The energy cost of going to Mars is less than 10 percent more than the energy cost of going to the Moon. The problem is the distance. An energy-efficient trajectory involves a travel time of nine months each way. The trip can be shortened to six or seven months at the expense of extra energy—a far cry from the week it takes to get to the Moon. The cost of transporting two years’ worth of supplies for even a small crew is daunting. Wernher von Braun was the first to make a technical study of a Mars mission in the 1950s, but it was hopelessly grandiose, using a thousand Saturn V rockets to build a fleet of ten spacecraft in Earth orbit to then carry seventy astronauts to Mars. He pitched a scaled-down concept to President Richard Nixon, but it was passed over in favor of the Space Shuttle. Former NASA administrator Thomas Paine tried next. Perhaps he’d watched too much
Star Trek
, but he aimed to conquer and industrialize the Moon with nuclear space tugs, launch a fleet of space stations into Earth orbit, and send several dozen spaceships a year to Mars to build a space station and support the colony. The Reagan administration was happy to shelve his report.

In 2014, the National Research Council revisited human flight, as directed by Congress. Its sweeping 286-page report concluded bluntly that NASA had an unsustainable and unsafe strategy that will prevent the United States from achieving a human landing on Mars any time in the foreseeable future.
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With current budgets, they suggest that it can’t happen before midcentury. Along the way, the report addresses the philosophical question of why we should send people into space at all, concluding that purely practical and economic benefits don’t justify the cost, but the aspirational aspect of the endeavor might make it worthwhile.

There must be good reasons and a strong will, because Mars is hard.

One risk is radiation. Earth dwellers are sheltered from high-energy cosmic rays and solar flares by our atmosphere and magnetic field. When the Curiosity rover headed to Mars, scientists switched on a radiation detector and found that the radiation environment in deep space is far more intense than it is on Earth. An astronaut on a two-year trip to Mars would get a 200 times greater radiation dose than an Earth dweller over that same period (
Figure 39
). However, to keep it in perspective, the adventure only increases the lifetime risk of cancer from 21 percent to 24 percent. The risk of spacecraft malfunction is likely to be much higher.

Another risk is weightlessness. We’ve talked about the substantial physiological changes resulting from a microgravity environment. Russian cosmonaut Valeri Polyakov spent 438 days aboard Mir, making a dizzying 7,000 orbits of the Earth, in part to see whether humans could handle a trip to Mars. The Russians reported that he suffered no long-term ill effects from his fourteen months in space. Robert Zubrin notes that the used upper stage of a Mars launch vehicle could be employed as a counterweight. With a mile-long tether and a spin rate of 2 rpm, Earth gravity would be simulated. With a spin rate of 1 rpm, it would be Mars gravity and the astronauts could get acclimated to the new situation before landing (
Figure 40
).

A third risk is being cooped up. Mars travelers would have to spend a year and a half in a cabin the size of a school bus, and as much as a year at their destination in a space no bigger than a large motor home. The Mars500 mission locked an international crew of six volunteers in a mock spaceship theoretically bound for Mars—when in fact they were sitting in Moscow for a year and a half. The crew “returned to Earth” in 2011. Most of them experienced severely disrupted sleep patterns and all of them reduced their activity levels in the confined space, something researchers call a behavioral torpor.
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The experiment made clear how important it will be to simulate Earth life rhythms in the spaceship or on Mars, and how important it will be to stay physically active.

It’s hard to judge the psychological impacts of such a trip. People who winter in Antarctica experience a diluted version of the problem, but travelers to Mars will be the most isolated humans who ever lived. They’ll have real-time interactions with a small number of companions and delayed communications with friends and loved ones who are tens of millions of miles away. They’ll be in a confined space with no option to simply go out for a walk, and they’ll be monitored continuously by anxious ground crews and scientists on Earth. If anyone spins out of control, there’s no real-time access to mental health services such as counseling or psychotherapy.

The visionaries are undeterred. Apollo astronaut Buzz Aldrin put it like this: “Going to Mars means staying on Mars—a mission by which we are building up a confidence level to become a two-planet species. At Mars, we’ve been given a wonderful set of moons which can act as offshore worlds from which crews can robotically preposition hardware and establish radiation shielding on the Martian surface to begin sustaining increasing numbers of people.”
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Two new ventures are trying to put Mars within reach without using any government resources. Inspiration Mars is the brainchild of Dennis Tito, the engineer-turned-tycoon who was the world’s first space tourist in 2001. Tito plans to keep costs down by not landing. His billion-dollar flyby plans to use an upgraded version of the SpaceX Dragon capsule. With a cleverly designed trajectory, he can get there with a single burn of the engine. The return is challenging, however. The capsule will slam into the Earth’s atmosphere at 32,000 mph, requiring new materials for a heat shield. The project is aiming for a launch in 2021.
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Mars One is run by Dutch entrepreneur Bas Lansdorp, who also plans to use a SpaceX capsule. He will keep costs down by leaving his four passengers on Mars. If they survive the trip, they will build a habitat from their spacecraft and adjacent inflated areas covered by Martian regolith. They’ll create water, oxygen, and some food locally, augmented by regular supply missions, and every two years they will be joined by four more refugees from Earth. Gradually, they will build a colony. Lansdorp estimates his costs to be $6 billion for the first trip and $4 billion for each crew that follows. Space experts judge the plan to be very ambitious; some judge it to be impossible. Everyone agrees it’s audacious.
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Would-be Martians are in a race against time. The red planet has its next close approach to the Earth in 2018, and it won’t get as close again until 2035. Inspiration Mars and Mars One have both had to slip past the most favorable 2018 launch date. Mars One accepted more than 200,000 applications online for the chance to live and die on Mars. In 2014, that number was culled to 1,058 from 107 countries, and then to 705. Those who remain will endure rigorous physical and psychological testing to generate a final group of twenty-four. Lansdorp plans to finance his venture by turning it into a reality TV epic—think
Survivor
meets
The Truman Show
meets
The Martian Chronicles
.
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Greening the Red Planet

Let’s ignore for a moment the evil twin. Venus is closest to the Earth in size and mass, and it has the same inventory of carbon dioxide. But on our planet most of the carbon dioxide is built into rocks and dissolved in the oceans, making them mildly acidic and leaving a moderately thick atmosphere to smooth out daily and seasonal temperature variations.

On Venus, only 30 percent closer to the Sun, the carbon dioxide built up in the atmosphere, triggering a runaway greenhouse effect and raising the surface temperature to a level where lead melts. Whoever named Venus after the goddess of love had a sad history of relationships.

Mars is the misbegotten sibling, the runt. It’s half the size of Earth with a third of the gravity. The next nearest Earth-like planet is tens of trillions of miles away, and unreachable with any current technology. The siblings went on divergent paths. One rusted and turned red, the other got the spark of life and turned green. Mars suffocated and dried out as its water and air leached into space, and it became scoured by dust storms and cosmic rays. Yet it’s at the edge of habitability, not much more inhospitable than a volcanic vent or a plateau in the high Andes. Mars has sunlight and reservoirs of water, carbon, nitrogen, and oxygen. One planet lived and the other died.

Perhaps we can make it live again?

One of the most audacious ideas in science is planetary engineering. Planets don’t stay the same. Geological evolution, combined with the aging of their parent star, can render a wasteland habitable and an Eden uninhabitable. This evolution occurs on geological timescales of hundreds of millions or billions of years.

Here’s how the Earth has changed. It formed 4.5 billion years ago and minerals show that there was liquid water within 100 million years, so conceivably life started then. If it did, it must have survived the “Late Heavy Bombardment” 3.9 billion years ago, when unstable orbits in the Solar System led to a surge of meteor impacts. Life around that time was limited to prokaryotes, or cells without nuclei, and there was no oxygen in the atmosphere. Around three billion years ago, bacteria evolved that produced oxygen as a waste product, which is poisonous to other kinds of bacteria. The oxygen content of the atmosphere rose 1.9 billion years ago and facilitated the evolution of eukaryotes, or cells with nuclei. Life diversified as it became multicellular and began to reproduce sexually. Dramatic episodes of glaciation almost obliterated life 2.7 billion and 700 million years ago. In the last 10 percent of the chronology, life finally became big enough to see without a microscope, plants and animals evolved, they moved onto the land, and a crescendo of evolution led to mammals, primates, and finally us. Dramatic change is normal for a biological world.
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More recently, we have been inadvertently altering our own planet through industrial growth and the use of fossil fuel. “Terraforming” is the process by which we might potentially alter a different planet to make it more Earth-like or habitable by terrestrial life forms.

The first step would be to raise the temperature on Mars just enough to release frozen carbon dioxide from the polar regions, triggering a runaway greenhouse effect. The positive feedback of this effect favors terraforming. While the carbon-dioxide atmosphere of Mars has only 1 percent of the pressure of the Earth’s atmosphere at sea level, there is enough carbon dioxide frozen in the soil to raise the pressure to 30 percent of the Earth’s. Robert Zubrin and Chris McKay have outlined several ways to accomplish this. Chris McKay is a NASA astrobiologist who believes we have an obligation to seed life on planets that might be habitable. One strategy is to fabricate a 100-kilometer mirror to direct extra sunlight toward the poles. Even if made from aluminized Mylar, such a mirror would weigh 200,000 tons. Being too heavy to launch from Earth, this would have to be constructed from materials refined on Mars.

Another method is to produce efficient heat-trapping gases on Mars, using industrial-scale facilities. There’s a rich irony in using methods to make Mars habitable that are in danger of rendering the Earth uninhabitable. These two methods would each use as much energy as a city like Denver or Seattle, and they would need hundreds of workers to implement. A clever, less costly idea is to redirect small asteroids to impact the surface of Mars. Carbon dioxide would be liberated by heat energy from the impact, and asteroids can deliver ammonia (a very efficient greenhouse gas) and dust, which will cause Mars to absorb more sunlight.
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