Rest easy, fans of solar-powered aeronautics. Captain Piccard's Solar Impulse has safely returned after 26 hours in the air -- powered by nothing but the sun. The four-engine aircraft, which features 12,000 solar cells arranged on its wingspan, reached a height of almost 29,000 feet before touching down at Payerne Airport near Berne, Switzerland today. The next step? The team is going back to the woodshed, with the hope of developing a plane that will circumnavigate the globe by 2013.