New Horizons Leads the Robotic Exploration of Earth’s Celestial Neighbors

A crowd watches in Central Park, New York City, as the Apollo 11 crew lands on the moon on July 20, 1969.

After a journey of nearly 10 years and more than 3 billion miles, on July 14 the New Horizons probe will fly within 7,750 miles of the surface of Pluto, becoming the first spacecraft to reach the dwarf planet. Pluto and its moon, Charon, are members of one of the last major unexplored regions of our solar system: the Kuiper Belt. New Horizons is an impressive reminder that, while America’s human space exploration program retools for its next steps, the United States continues to lead the robotic exploration of Earth’s closest celestial neighbors.

America has led exploration of the solar system

By exploring Pluto and its neighborhood, New Horizons is upholding the tradition of American leadership in robotic space exploration. An American probe, Mariner 2, became the first human-built spacecraft to ever encounter another planet when it flew past Venus in 1962. Mariner 4, meanwhile, became the first spacecraft to fly past Mars in 1965—50 years to the day before New Horizons is scheduled to fly past Pluto. Six years later, Mariner 9 became the first human-made object to orbit another planet when it entered into Martian orbit. Finally, the United States completed preliminary reconnaissance of the inner solar system when Mariner 10 flew past Mercury in 1974.

Exploration of the outer solar system by American probes was not far behind. Pioneer 10 became the first spacecraft to fly by Jupiter in 1973, while Pioneer 11 became the first spacecraft to encounter Saturn in 1979. In 1986 and 1989, Voyager 2 completed its “grand tour” of the outer solar system, flying past Uranus and Neptune.

The United States was not just the first country to send early explorers to all eight planets in our solar system. It was also the first—and so far the only—country to successfully land robots on Mars. Two Viking landers touched down on the red planet less than two months apart in 1976, sending data back to Earth for six and three-and-a-half years, respectively. It would be 21 years until the next successful Mars landing, when NASA’s Pathfinder lander hit the surface on July 4, 1997, and deployed the first Mars rover, Sojourner, shortly thereafter. Four more landings would follow: rovers Spirit and Opportunity in 2004, the Phoenix lander in 2008, and most recently the rover Curiosity in 2012.

The achievement of landing spacecraft on Mars on seven occasions should not be underestimated: The Soviet Union tried and failed to land on Mars three times in the 1970s. The European Space Agency’s Beagle 2—named after Charles Darwin’s ship, the HMS Beagle—also failed in its 2003 landing attempt. And other American attempts have not been wholly successful, such as when the Mars Polar Lander crashed into Mars in 1999.

Continued advancements despite budgetary issues

Since the initial reconnaissance missions of the 1960s and 1970s, the United States and its international partners have launched 22 successful robotic missions to Mercury, Venus, Mars, Jupiter, Saturn, and the asteroid belt. Today, the United States has seven active robotic explorers in addition to New Horizons: five, including rovers Opportunity and Curiosity, exploring Mars; one in the asteroid belt; and one, Cassini, in orbit around Saturn. What’s more, both Voyager probes continue to send back data to Earth, even after Voyager 1 officially crossed into interstellar space in August 2012.

But the future of robotic space exploration is just as cloudy as its human counterpart. NASA’s Juno mission is en route to Jupiter and scheduled to arrive next year. Two more probes are slated to launch in 2016: OSIRIS-REx, intended to retrieve samples from the asteroid Bennu, and InSight, a Mars lander. Another Mars rover is on the drawing board with a planned launch in 2020, and initial funding for a mission to search for life on the icy Jovian moon of Europa has been included in this year’s NASA budget. But budgetary constraints are as likely hinder America’s robotic space exploration program as they do its program for human spaceflight.

For now, though, budget worries can wait. New Horizons’ encounter with Pluto offers an opportunity to reflect on the vast knowledge that has been gained in the 53 years since Mariner 2 became the first spacecraft to visit another planet. Thanks in large part to U.S. leadership, humanity knows far more about its own small corner of the universe than it did just half a century ago. Pluto, Charon, and the Kuiper Belt represent the last unexplored nook of that small corner. If all goes well on July 14, Americans can once again bask in the pride that comes from leading—and completing—humanity’s initial exploration of its own celestial backyard.

Peter Juul is a Policy Analyst at the Center for American Progress.