Humankind is marking an off-the-planet pinnacle Monday: the 15th anniversary of continuous residency at the International Space Station.
NASA and its global partners are celebrating the milestone, as are the six men aboard the space station. The U.S., Russian and Japanese crew plans a special dinner.
Commander Scott Kelly, who's on a yearlong mission, says the biggest benefit of the orbiting lab is furthering long-term exploration goals. He and his crewmates consider the space station a bridge or test bed for the technology needed to travel to Mars.