Why should we engage in human exploration of space? Why should we go to Mars? We must recognize that these two questions are inextricably linked, and we must answer the first before we can even address the second.

We must explore space and we must go to Mars. Why, you ask? For these three reasons.

I. THE NATURE OF US

We are an expansionist species. This is neither good nor bad, it is simply how we are. Our species started out as a small group of not particularly impressive hominids in the East African Rift Valley. Today we dominate the globe. We are the most astoundingly successful large animal ever to inhabit this planet, in terms of shear numbers and variety of habitats, if not yet longevity.

This success was not inevitable. Approximately 74,000 years ago a super volcano erupted in Toba, Sumatra. The fallout from this massive eruption caused a drastic change in climate, a volcanic winter. Mitochondrial DNA evidence strongly suggests that humanity was nearly destroyed by this event, our numbers falling as low as a few thousand individuals. We were very nearly extinct, surviving perhaps in only a few tropical areas which remained relatively warm.

Yet today, a geological eye-blink later, there are over 6 billion of us, and we live in very nearly every habitat on this globe. Mountains and valleys; jungles, forests, and plains; great cities and lonely deserts; today humans call all these places by the same word: “home”.

The Earth is a finite place, however, and sooner or later we were bound to run out of room for expansion. That is happening right now. Desertification, erosion, loss of tropical rainforests, receding water tables, wholesale destruction of other species, pollution, and climate change are all indicators that we are running out of room on this planet. There is increasing friction worldwide over access to clean drinking water, in some places threatening to break out into armed conflict. (This is an under-appreciated aspect of the strife in the Middle East). Competition for other increasingly scarce mineral resources is also on the rise.

We face a stark choice. We can divide into warring tribes and fight over the finite resources of this planet. There are no winners if we make this choice; it must lead, perhaps slowly or perhaps quickly, to the destruction of humanity. Or we can continue the lightning-fast expansion of our species in the one direction left us, up. Space is the next logical step for our expanding human experience.

II. ATTITUDE IS EVERYTHING

Societies, like individuals, can make a choice about how they live. They can be active, dynamic and energetic, thereby choosing their own destiny; or they can be passive and sedentary, and allow others to make that choice for them.

In the Fifteenth Century, two great civilizations each embarked on a series of overseas voyages. The history of the European Age of Discovery is well known, starting with the Portuguese and carrying on with the Spanish, Dutch, English, and French explorers who followed them. Less well-known are the seven great voyages carried out in the first third of the century by the Chinese under the great admiral Zheng He. These were far larger and grander expeditions than anything mounted by their European contemporaries, consisting of hundreds of magnificent ships with as many as 40,000 men. However, the differing purposes of these expeditions were of far more consequence than their relative size, or how far they journeyed, or how many new lands were discovered.

The Europeans had two primary motives: discover and claim new trade routes and spread Christianity. The key element here is the willingness to look for and embrace the new, to discover things that were previously unknown. In the process, Europe was treated to centuries of constant intellectual and economic stimulation.

China had always been inward looking. This attitude was fostered by centuries of Confucian tradition which emphasized filial piety toward one’s ancestors, and, by extension, to the emperor. China had a long and continuous cultural history, which led to an ingrained sense of national superiority. The seven great voyages of Zheng He were thus specifically not voyages of discovery, or trade, or conquest. This would have implied that there was something China wanted or needed, but did not have. For China, this was literally inconceivable. These voyages were thus magnificent and expensive political statements, meant to produce awe in the kingdoms they visited, and thus cause them to declare their fealty to the Emperor. In this, they were quite successful, gaining vassals as far west as Mecca, and even Madagascar. The key element here is that they were political statements, and thus disposable. These voyages brought back nothing that was vital to China, they served no core national purpose. In 1434 a new emperor took the throne. With his ascension, a new party opposed to the overseas voyages gained power. The great fleet was dismantled, and gradually over the next few decades China closed herself off from any outside contact. She literally burned her boats.

By the Nineteenth century expanding Europe met hermetic China. At the beginning of the European Age of Discovery, China probably held a technological and economic advantage. By the time the two societies collided, Europe had completely outstripped China. Chinese armies carrying swords and spears met European troops equipped with repeating rifles, breech-loading cannon, machine guns and iron-clad battleships. The result was 150 years of chaos, foreign occupation, humiliation, and revolution. Only in the past two decades has China begun to emerge from the tragic consequences of her self-imposed dis-engagement from the world.

Five hundred years ago the West took the initiative, embracing a willingness to discover and use new knowledge and to build and expand their economies. China closed herself off to new knowledge and experience. Western civilization created an energetic, dynamic, and successful society, while China slowly lapsed into sedentary senescence.

Today we face the same choice. We can embrace the new challenge of space, and thus continually re-invigorate our society. Or we can close our backs on new experiences, and lapse slowly into decay. At the end of the Apollo program we dismantled the factories which built the mighty Saturn V rocket and threw away the blueprints. We have already burned our boats once. China’s recent launch of a manned space craft indicates that they have taken to heart the hard-won lessons of history. Will we?

III. WE ARE NOT INVULNERABLE

Human beings dominate the Earth today, and we thrive by embracing new challenges. But we are no more immune to the laws of nature than any other species. I have already mentioned the Toba super-volcano and its near annihilation of our species. There is evidence of numerous other massive eruptions throughout the Earth’s history, and there is no guarantee that there will not be a repeat.

There is ample evidence of past meteorite strikes on Earth. The Tunguska explosion at the beginning of the last century is a familiar example of a relatively small impact. The extinction of the dinosaurs some 60 million years ago is commonly credited to a much larger strike. The most dramatic example, however, was the comet Shoemaker-Levy 9, which produced a magnificent cosmic display when it impacted Jupiter in 1994. For many people, this made real the possibility of Earth receiving a similar hit.

Easter Island is best known for its great stone faces. These enigmatic visages beheld a dark history. Today the island is a stark, barren place. But that is not what the first inhabitants found. The island was once covered with a species of giant palm, now extinct. The settlers cut down trees for farming, houses, firewood and boats. Erosion set in and washed away the topsoil. Crops failed. Clans fought each other. By the time they sought to escape, it was too late. They could no longer build the boats they needed because they had cut down, literally, all the trees. So they starved.

Human civilization faces many potential perils, both natural and man-made. The only way to provide a truly secure future for humanity is to spread our reach beyond the home world. We need to create new branches of human civilization throughout the inner Solar System. We must take some of the eggs out of the basket.

IV. SO WE MUST GO, BUT WHERE?

Space is a big place. But our choices of where we might send human explorers are limited. Our current propulsion technologies preclude sending humans much further than our closest neighbors in our own solar system, meaning the Moon, Venus or Mars.

Venus is not an attractive destination. The surface temperature on Venus is hot enough to melt lead. The atmospheric pressure is sufficient to crush a spaceship like a soda can. It is a hellish world where humans cannot survive.

We have been to our own Moon, and the idea of going back more permanently is no stretch of the imagination. However, the Moon lacks key resources that would be needed to support humans. There is some recent evidence of water ice hiding in crater shadows, but there does not appear to be very much of it. We could produce oxygen on the Moon from the lunar regolith, but it would require significant industrial infrastructure and imports to do so. Lunar gravity is about one sixth of Earth gravity, and it is unknown what long term health risks this would cause. The Moon is probably the most geologically stable place we have yet found, however, which makes it very attractive to astronomers who need a stable base for their highly sensitive instruments, as well as protection from light and radio pollution. It is likely that we will establish a manned research base on the Moon, similar to what we have now in Antarctica, but large scale settlement is unlikely.

This leaves Mars, which is very attractive for human settlement. Mars is by far the most Earth-like planet in the solar system. It is slightly smaller, with gravity 38% of Earth’s. This is still about double the lunar gravity, and is probably enough to allow for normal walking, unlike the moon. The Martian day is very close to the earth day, at about 24 hours and 37 minutes, and Mars undergoes the same four seasons we have on Earth. There is abundant and growing evidence for the presence of water on Mars, in the form of polar ice deposits, permafrost, and underground aquifers. Water-carved features are everywhere on Mars, indicating that the planet was once warm enough to support liquid water on the surface. Mars has an atmosphere. It is extremely thin and composed mostly of carbon dioxide, but it is thick enough to provide some protection from radiation exposure, and to allow sound to travel. Mars has volcanoes. At first, this might sound like a negative, but volcanism is one of the key processes for creating and distributing important minerals. Mars has abundant supplies of every key mineral and element of interest to industry. Mars is roughly equivalent to all seven Earth continents in land area. Production of oxygen, food and fuel is relatively easy on Mars, with relatively small imports required, making exploration and settlement much easier and cheaper. Mars is the only place in the solar system, other than Earth, that can grow crops in a surface greenhouse. Mars is clearly the best destination for human explorers.

THE MARTIAN IMPERATIVE

There are thus three reasons we must explore space and settle Mars. We must find a new frontier or descend into conflict; we must explore and discover to maintain our vitality; and we must protect the future of our descendants. For the sake of our species, our civilization, and our nation, we must make Mars the home for a new chapter in the epic of humanity.