by Chris Impey
To the next generation of space pioneers,
who will realize their dreams to
live off-Earth.
CONTENTS
PREFACE
PART I. PRELUDE
1. Dreaming of Beyond
2. Rockets and Bombs
3. Send In the Robots
PART II. PRESENT
4. Revolution Is Coming
5. Meet the Entrepreneurs
6. Beyond the Horizon
7. A Plethora of Planets
PART III. FUTURE
8. The Next Space Race
9. Our Next Home
10. Remote Sensing
11. Living Off-Earth
PART IV. BEYOND
12. Journey to the Stars
13. Cosmic Companionship
14. A Universe Made for Us
NOTES
CREDITS
INDEX
Preface
Space is inhuman. We can’t survive unprotected in a pure vacuum for more than a minute. Going there involves being strapped to a barely controlled chemical explosion. Low Earth orbit is equivalent to half an hour’s drive straight up, but it’s insanely expensive to get there. The set of people who have experienced zero gravity is one of the most exclusive clubs in history. Yet space travel is an expression of a fundamental human trait: the desire to explore.
This book is an exploration of the past, present, and future of space travel. We’re on the cusp of an important transition, where diverse technologies have matured to the point where space travel could be routine. A cadre of innovators and entrepreneurs is about to deliver space travel that’s not just for astronauts and the super-rich. It will happen sooner than you think.
Each of the four parts of this book is preceded by a fictional vignette delivering us into the world of a young pioneer about to undertake a journey to the stars. First, we look at the “Past” to learn about our genetic proclivity for exploration and our progress with rocketry that let us leave the Earth for the first time in the mid-twentieth century. We also learn about the highs and the lows resulting from that landmark achievement. Then, in the “Present,” we see that the malaise of the space program will be cured by a new generation of entrepreneurs who are transforming our potential to leave the planet. We examine the legal and regulatory barriers that stand in their way and consider the dangers faced by space travelers. Peering into the “Future,” we look at how we can travel to the Moon and Mars, and we investigate the technologies needed to establish colonies there. We meet the robots that will be our partners in space and we visualize a time when off-Earth humans become a new species. Finally, we speculate “Beyond” our current capabilities to the time when we can travel to the stars and become citizens of the Milky Way. In a universe built for life, our yearning for cosmic companionship is strong, and we may never realize our full potential as a species if we stay Earthbound.
I’m grateful to Anna Ghosh for stalwart support of my writing career, and Tom Mayer and Ryan Harrington at W. W. Norton for helping to forge a better book. I’ve benefited from conversations with many colleagues over the years, but any errors or misstatements that remain are my responsibility alone. My deepest gratitude goes to Dinah Jasensky for her love and encouragement of all my writing endeavors.
PART I
PRELUDE
I was four years old when I was chosen to be a Pilgrim. Too young to understand what that meant, I heard my mother try to describe it, but her words made no sense, so I fixated instead on the mixture of excitement and fear in her voice.
A few years later, the implications came into better focus. I suffered difficult years in a normal school, where I was alternately ostracized and bullied, ignored and humiliated, with a relentlessness seen only in children. To be a Pilgrim was an extraordinary honor but it marked me as different, as other. It was a relief when I was plucked from there at age eight and sent to a special school called the Academy, a school for my kind.
The Academy was in Switzerland, on a mountain lake that sparkled aquamarine in the sunlight, in a special compound where we were shielded from the media and prying eyes. There were nearly 300 of us, from more than fifty countries. We got one trip home every year but no family member could visit the school. Video chats with outsiders were limited to an hour each week. It may sound harsh, but it was for our own good.
We ranged in age from seven to twelve. I was one of the youngest. There were equal numbers of boys and girls. With so many cultures and languages represented, it could have been like Babel, so most of us wore our digital translators all the time. The curriculum was also polyglot. We studied everything from engineering and philosophy to medicine and fine arts. With as many tutors and counselors at the Academy as students, we had plenty of help. Expectations were high and there was a gentle but persistent pressure to excel. The staff was aloof, no doubt instructed not to form emotional bonds with us. Some of them were psychologists and psychiatrists who were clinical and often cold in their detachment.
I remember my dreams from that time.
Large shapes moving around in the darkness. An unrelenting pressure in my chest. A door sliding up, an inch from my face, like the lid of a coffin. A window, and beyond it, nothing, an absolute void. The images were both inchoate and sharply real. I would always wake with a start and sit up, bathed in sweat, my breathing fast and shallow.
On my mother’s last visit before I left the Academy, a few months after I turned seventeen, she told me how my father died. I never knew the details when I was young, and information at the Academy was tightly controlled. He was on his second tour of a mining station on Phobos. His crew was deep in a shaft looking for inclusions of platinum and iridium. Miscommunication with the surface crew caused them to set off a charge nearby. Sofa-sized slabs of rock were ejected from the face of the shaft. At the center of a small asteroid there’s no gravity, so no way to be crushed by falling rock as on Earth.
But Newton’s laws have their own implacable logic. A large rock hit him squarely in the chest and carried him to the opposite wall, where its momentum was transmitted into his body, crushing and killing him instantly.
That’s probably part of why I was chosen. My father was a space rat and my sister an accomplished pilot; I had space in my genes. But at the Academy there were many kids with no predisposition to technical subjects; their parents were musicians or artists or diplomats. No two of us were alike. We seemed to form, as intended, a miniature world.
At my graduation, my mother and my sister were in the auditorium, and they grinned ear to ear when I waved to them. Later, as we shared a meal in the dining hall overlooking the lake, I flashed back to the way my mother’s voice had sounded a decade earlier. Her excitement and fear had morphed into quiet pride tinged with sadness.
After graduation, we had two weeks to pack up and say our farewells. Visits and video chats were unlimited. I remember that it was emotionally exhausting to spend so much time with my family. Many of the other students felt the same way. We were young adults and had grown up without them, with only each other for sustenance. I felt relieved when the time came to travel to the launch site, though that relief was followed swiftly by a wave of guilt.
The time had come to learn what it meant to be a Pilgrim.
To be an emissary of Earth in the late twenty-first century. To be in a small group chosen for a unique experiment. The experiment was designed by sober scientists and engineers but it had the trappings of madness. We were human seedlings, charged with taking root in a new world.
1
Dreaming of Beyond
_______________________
Out of Africa
When we were just one million strong, did we dream about what lay
beyond?
Two hundred thousand years ago, anatomically modern humans first emerged in Northeast Africa.1 The cradle of our creation was the place now known as Ethiopia. Over the next hundred thousand years, these humans spread across Africa. Our distant ancestors kept no journals and, as far as we know, they had no written language. Only bones and scattered artifacts survive. Those artifacts speak of a rugged, doughty species that ceremonially buried their dead, hunted with sharpened flints made into spears and arrows, and daubed paint on cave walls to record the iconography of their lives. Their evocative images, which must have seemed kinetic in the flickering glow of an oil lamp or a fire, speak to us across the millennia of their fears and dreams.
Modern genetic techniques have allowed us to reconstruct their journey out of Africa—an epic migration as audacious as our first steps into space many millennia later.
Life on Earth is united by a single genetic code. A four-letter alphabet of base pairs encodes the unique function and form of every organism. The four bases—A for adenine, C for cytosine, G for guanine, and T for thymine—form the rungs of the twisted ladder that is DNA. A pairs with T and C pairs with G across the ladder; when the ladder splits down the middle, each side is the template for a new DNA molecule. The genetic code specifies the sequence of twenty amino acids used by living cells to build proteins.
If the genetic code were perfectly transcribed and expressed, there would be no evolution and life would be, well, boring. It would also be a dead end, since it couldn’t adapt and survive over time. One type of variation occurs when the genetic blueprint, the genotype, is expressed in a particular environment, the phenotype. Two cloned seedlings will develop quite differently when one grows in loamy soil and the other grows on a windswept mountain. A second type of variation occurs over time when the genetic material is altered by mutation or imperfect copying. Biodiversity cascades as variations grow over time and are culled by natural selection. As a result, the DNA of life has developed a tangle of branches that emerge from the root, a “last common ancestor” four billion years ago.2 This primitive cell was the precursor of all plants and animals and the mother of all microbes. Creatures that reproduce sexually, like humans, mix their DNA in a way that makes everyone unique from their parents. This accelerates genetic variation and evolution, particularly in small populations.3
Genetic anthropology is the use of DNA and physical evidence to trace human migration. We all contain DNA from our last common ancestor, which is how we know when and where humans originated. DNA mixes due to sexual reproduction but some special sequences of DNA pass unaltered from parent to child. For example, the Y chromosome passes only from father to son and so allows men to trace paternal lineages, while mitochondrial DNA passes only from mother to child and so allows both men and women to trace maternal lineages. Both of these sequences of DNA are subject to occasional harmless mutations that become inheritable genetic “markers.” Within a specific geographic region, any particular genetic marker spreads quickly and after several generations it’s found in almost every member of the local population. When people migrate from a region, they carry that marker with them. By studying different genetic markers in many indigenous populations, scientists map out early human migration.
The Genographic Project has painted a picture of human migration using “brushstrokes” of DNA from more than 70,000 members of carefully selected indigenous tribes around the world. Appropriately, most of the funding comes from the National Geographic Society, which has turned from exploration of the planet to exploration of the inner world. The project is not without controversy, as some indigenous peoples have declared it exploitative and have declined to take part. However, the project has gained a big boost from crowdsourcing. More than 600,000 people have received their genetic histories in return for contributing DNA to an open-source database.4 With such a rich resource and powerful computers to apply to it, more than 100,000 genetic markers have been identified in the past decade. The leader of the project is Spencer Wells, a National Geographic explorer-in-residence. He says: “The greatest history book ever written is the one hidden in our DNA.”
Our DNA tells the story of the profound human urge to explore.
Around 65,000 years ago, we first ventured out of the continent of our origin. The route from the Horn of Africa to the Arabian Peninsula was probably across the Bab el-Mandeb strait. Today that strait is one of the world’s busiest shipping lanes; at that time, after the last ice age had lowered sea levels, it was merely a narrow, shallow channel. The tribe that ventured out of Africa may have been only a few thousand strong. It was not a single expedition but a series of small clans of loosely related family members leaving over a period of centuries. They prospered as they dispersed, starting settlements in Central Asia and then in Europe. By 50,000 years ago, they had spread to southern China and Australia. By 40,000 years ago, they’d spread throughout Europe. Populations prospered thanks to hospitable conditions in southern Europe and Asia.
The last stage of the migration was audacious and dramatic. Despite more favorable climates around the Mediterranean and in the Middle East, some nomads ventured northward. The most recent ice age was sharpening, but these intrepid humans spread in an arc across the Siberian tundra. Vast ice sheets had sucked much of the moisture out of the Earth’s atmosphere and dropped sea levels hundreds of feet. This allowed our ancestors to traverse the land bridge across the Bering Strait about 16,000 years ago. There’s evidence they reached southern California just 3,000 years later. It took them only another few thousand years to travel south most of the way through the Americas. Looking at a map of the journey, where our ancestors moved from the frozen wastes of Alaska to the bleak landscape of Patagonia, it seems astonishing that they traveled so swiftly—the migration couldn’t have been motivated simply by food and shelter.
The timeline just described is affected by the possibility that humans migrated by sea. There is some indication that small groups made the arduous voyage across the Atlantic from Europe to North America 25,000 years ago, clinging to the edge of the ice pack. In Australia, a single lock of Aboriginal hair is rewriting the story of how that continent was populated. The traditional explanation is that some humans who had left Africa moved east and settled in Australia after a sea voyage from Southeast Asia. But in 2011, gene sequencing of hair donated to a British anthropologist in 1923 showed that Aboriginal Australians are more closely related to Africans than they are to Europeans or Asians. So present-day native Australians may be the oldest group of humans living outside Africa.5
After tens of thousands of generations on the African savanna, we spread across the Americas in a few hundred (Figure 1). This rapid, purposeful exploration of new worlds is in its way as dramatic in terms of leaving our comfort zone and embracing the unknown as our decision to leave the Earth when we developed the technology to do so.
Figure 1. Map of early human migrations, based on DNA in mitochondrial genomes. The migration routes are marked in years before the present day. Different shadings are for Homo sapiens (1, dark gray), early hominids (3, mid gray), and Neanderthals (2, light gray).
Genetic material can tell us how we spread around the world, but it can’t tell us why. For that, we have to look into our natures.
The Urge to Explore
Epic animal migrations are driven by climate, the availability of food, or mating, and almost all animal migrations are seasonal. Humans are the only species that moves systematically and purposefully over very large distances, in multigenerational migrations, for reasons not tied to the availability of resources. The itch that led our ancestors to risk everything to travel in small boats across large bodies of water like the Pacific Ocean is related to the drive that will one day lead us to colonize Mars. Its origins lie in a mixture of culture and genetics.
Behavioral psychologist Alison Gopnik has observed that humans are unique in the way they connect play and imagination. Mammal species can be playful when they’re young, but the play
is quickly channeled into practicing skills such as hunting and fighting, which are needed as an adult. Human children spend a proportionally longer time in a world where their development is sheltered and facilitated by adults.6 We play, according to Gopnik, by creating hypothetical scenarios that allow us to test hypotheses—acting in effect like miniature scientists. What happens if I mix these two liquids together? If I go through the woods, will I be able to remember enough landmarks to find my way back? Can I make my Lego bridge span the gap from the sofa to the coffee table? Children are fearless hypothesis machines. After the child develops the necessary motor skills, mental exploration then leads to investigation of the physical environment.
The development of hypothetical scenarios through play isn’t needed for survival and the tendency for mental exploration is peculiarly human. Restlessness isn’t only in our minds; it’s also in our genes.
We share more than 95 percent of our DNA with monkeys and apes, so we have great commonality with our most recent ancestors. Yet certain developmental genes gave us an edge over apes and other hominids: We have lower bodies built for walking long distances, hands that are better for manipulating objects, and brains with larger language and cognition regions. These genes are regulated by regions of DNA that used to be labeled “junk” but are now recognized as being keys to understanding how a species evolves.7
One particular gene has received a lot of attention because of its central role in controlling one of the most important neurotransmitters. DRD4 is one of the genes that control dopamine, a chemical messenger that influences motivation and behavior. People with one of the variants of this gene, called 7R, are more likely to take risks, explore new places, seek and crave novelty, be extroverts, and be hyperactive. About one person in five carries DRD4 in the 7R form.
Figure 2. Correlation between the frequency of DRD4 alleles and long-distance migration among 39 population groups over the past 30,000 years. In modern populations, the long or 7R variant of this gene is associated with attention deficit hyperactivity disorder (ADHD).