Thomas Jefferson was a believer in the exploration and colonization of new lands. Indeed, he did more to explore and settle the American West than any other president. He engineered the Louisiana Purchase, sent the Corps of Discovery and other exploratory missions to map and chart the land, and laid down the principles for future legislation (such as the Homestead Act of 1862) that made the settlement of the American West possible.
Jefferson believed that the existence of vast amounts of land to the west of the original 13 colonies was the greatest blessing America possessed. It allowed future generations the chance to recreate America over and over again, starting afresh in new lands. Jefferson called it the "Empire of Liberty" and believed it would lead to "the age of experiments in government." Innumerable communities would be able to decide for themselves how they would be governed, and the great diffusion of humanity across the continent would, Jefferson hoped, ensure that no powerful central government would be able to control the entirety of them.
While much of what Jefferson foresaw did come to pass, as can be seen in the Jeffersonian spirit that still pervades small towns throughout the Midwest, it must be admitted that the continent is all filled up now. In Jefferson's time, a person dissatisfied with his life in Boston or Philadelphia could head west to start his life over again. In our time, with no open frontier, this option no longer exists. As Jefferson understood very well, societies have no open frontier will eventually stagnant and decay.
This is why space exploration should be an important priority for 21st Century Jeffersonians. A Jeffersonian society can only exist if there is a frontier to act as a social steam valve, and with the Age of Exploration long since relegated to the history books, there are no open frontiers on Earth any longer. If 21st Century Jeffersonians want to find a new frontier, they must look to the stars.
Of all the planets in the Solar System, Mars is certain to be the first which is explored and settled by human beings. Even now, three robotic spacecraft (two American, one European) are orbiting the Red Planet, while the plucky robotic rovers Spirit and Opportunity wander its landscapes as they conduct geological studies. NASA has declared that human expeditions to Mars are its long-term goal, and we will hopefully see the first men and women exploring the Red Planet within the next twenty years.
Some visionaries are looking forward to the day when permanent human settlements will be established on Mars, an event which would reopen the frontier to humankind and mightily advance Jeffersonian ideals. One such man is Robert Zubrin, founder of the Mars Society. More than just about anyone, he has put the exploration and colonization of Mars on the map as an achievable goal.
Watch this documentary (in five parts) about Zubrin and his work. It is certainly a vision of which Jefferson would have strongly approved.