SPACE EXPLORATION
We stand at the threshold of a new Renaissance, a moment much like the morning of the modern age when most of the globe lay deep in mystery. What a time this is to be alive! Today's young will live to see settlements in space, unlimited energy from fusion, and explosions of knowledge on all frontiers—from the workings of the brain to the origin and nature of the cosmos itself.
The Vision
For centuries, people have dreamed of leaving the Earth and traveling through space to visit the moon and explore other planets and stars. During the past thirty years, some of these dreams have become realities. Spacecraft have orbited the Earth and sent back data to ground-based scientists. They have traveled to other planets and transmitted images and information that have helped to expand our knowledge of the solar system. People have gone into space to orbit the Earth and even to visit the moon.
In 1992, a United States satellite, the Cosmic Background Explorer (COBE), detected slight variations or ripples in the background microwave radiation coming from far out in space. This information may be helpful in determining how the universe evolved.
Despite such achievements, space exploration is still in its infancy considering the vast scope of the universe and the many unanswered questions about it. For example, scientists estimate that there are 10 billion stars like our sun in the Milky Way galaxy, perhaps a million of which may have planets orbiting around them. Scientists want to know if these planets exist, and if they do, are any of them like those in our solar system, or do any harbor intelligent beings or other forms of life.
Someday, as a result of space exploration and travel, scientists may be able to solve the mysteries of the universe. Their discoveries will change our view of life on Earth and of our planet's role in the universe.
Achievements in space have been truly remarkable. Yet the future may hold even greater triumphs. The day may come when human beings explore and inhabit the distant reaches of space and unravel the mysteries of the universe and of life within it.
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Future Space Explorations
One of the central quests of space exploration is to discover whether life exists anywhere else in the solar system. Life as we know it has evolved on Earth because the planet lies at just the right distance from the sun to allow water to remain liquid and temperatures to be moderate. Without these two conditions, life-forms as we know them could not exist.
Search for Life on Other Planets
Among the planets, Mars appears to be the most hospitable to life, although it is farther from the sun and much colder than Earth. Mars has some water, frozen in polar ice caps and perhaps in its soil, much like the permafrost in Earth's arctic lands. Mars also has a thin atmosphere, composed mostly of carbon dioxide. Scientists think that long ago the planet may have had sufficient amounts of atmosphere and surface water to support life. Although studies of the planet's surface have not revealed any signs of life, future probes will no doubt look for remnants of life at the sites of Martian lakes that no longer exist.
Some scientists believe that remnants of Martian life may have already been found in several meteorites thought to have come from Mars and crashed on Earth. In the late 1990's, NASA scientists discovered tiny wormlike features resembling fossilized bacteria in meteorites found in Antarctica, Egypt, and India. The meteorites varied in age from 4 billion years to 165 million years, suggesting that life once existed--and perhaps still exists--on the red planet. Other researchers were skeptical, arguing that the microscopic features might not be signs of life at all. The debate will no doubt continue until more convincing evidence can be found in samples of Martian soil brought back to Earth by future space probes.
Another possible candidate for life in the solar system appears to be Europa, Jupiter's large ice-covered moon. Scientists think that some form of life could exist under Europa's ice, just as it does in frozen lakes of Antarctica.
In the late 1990's, the Galileo space probe found signs of ice that had melted and shifted, indicating warm slush or even liquid water beneath Europa's cracked icy surface. Some scientists speculate that a gravitational "tug of war" exerted by Jupiter and its other moons could keep large parts of Europa's ocean liquid. If that is so, then Europa may harbor some form of marine life--perhaps similar to creatures found thriving around hot deep-sea vents on Earth. Future space probes, designed to peer below Europa's surface using ice-penetrating radar, may offer further clues.
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Human Bases and Colonies in Space
Sometime in the future, we will establish permanent bases on the moon and Mars. The moon is the most likely site because it is close to Earth and its weaker gravity would allow spacecraft to use less fuel when taking off from its surface. The moon's surface also contains various mineral resources that could be used in building a base.
In 1998, the space probe Lunar Prospector, in orbit above the moon's poles, found signs of frozen water--the raw material from which hydrogen fuel and breathable oxygen could be extracted and used by future lunar colonists.
If we establish bases on the moon, these bases will be excellent sites for astronomical research. The far side of the moon, for example, would be ideal for telescopes because there would be no glare from the sun and no atmospheric distortion.
With near-perfect viewing conditions, astronomers could search for planets around other stars in the galaxy, conduct long-term studies of stars and other distant objects, and look much farther into space than with any Earth-based telescopes. The moon would also be an ideal site to listen for radio signals that might come from intelligent life elsewhere in the universe.
Much farther in the future lies the possibility of voyages to other stars. With current methods of rocket propulsion, however, a trip to the nearest star would take many more years than exist in a person's lifetime. Space travel within our Milky Way galaxy, therefore, will probably require spaceships to be "colonies," with generations of inhabitants whose entire lives will be spent on board the space colonies as they travel on their journeys.
Given enough time and advances in technology, it might even be possible to colonize other parts of the galaxy. In the 1990's, scientists began discovering evidence of planets orbiting other stars beyond our own. It may also be possible to build floating space colonies around nearby stars. These colonies would be located in regions of space near enough to a star so that there would be enough light, heat, and solar energy for human beings to survive.
More practical than colonies far out in space would be an orbiting space colony near the moon with room for 10,000 people. The colony could be built of lunar material, which would be easy to transport from the moon's surface because the weak gravitational force would allow rockets to take off easier than they can on Earth. Solar energy would supply an unlimited amount of power to the colony.
The Days Ahead
While exciting to contemplate, centuries-long space voyages, bases on the moon, and human colonies in space will not come about for many years. However, space tourism has become a reality. In 2001, American businessman Dennis Tito became the first civilian to pay for a trip into space. He joined a Russian crew on an eight-day mission to the International Space Station. Others lined up immediately for their turn in space.
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