Planets

People have been watching planets, moons, and comets wander amongst the stars for millennia. Yet it was always "look, don't touch" until 1969, when NASA sent two men to Earth's moon – and they came back with lunar rock and soil for scientists to study.

Since those first footsteps, NASA has broadened its reach with an increasingly sophisticated series of explorers that have landed on asteroids, tasted the swirling gases of Jupiter's atmosphere, and collected the breath of the Sun. Just in the past few years, we have:

• Discovered potential liquid water on what was once thought to be a cold, dead moon of Saturn
• Gathered compelling evidence that Mars once had saltwater seas on its surface
• Listened in as the Voyager spacecrafts' daily reports sent us the sound of a solar blast wave

In the next few decades, NASA intends to deepen our understanding of the solar system, with spacecraft fanning out to destinations from the innermost planet to the very edge of our Sun's influence. Some will stay in Earth's orbit, others will follow looping one-way trajectories through the gravitational forces of the planets, and a few will come back carrying priceless souvenirs from the other worlds.

Our intensive investigation of Mars will continue, from orbit and on the surface. Advanced robotic missions are critical to the Vision for Space Exploration.

We will study the Kuiper Belt, and the comets that come from it, to investigate the primordial substances which evolved into the Solar System. Our Saturn orbiter launched a European probe to the thick, water-and-organics-rich atmosphere of Titan, Saturn's largest moon, and collected images of the surface of Europa, a moon of Jupiter which might have oceans of liquid water underneath an icy crust. These moons may have all of the components required for life – they may hold many clues to our own planet's development.

Our Solar System is a place of beauty and mystery, incredible diversity, extreme environments, and continuous change. Our Solar System is also a natural laboratory, on a grand scale, within which we seek to unravel the mysteries of the universe and our place within it.