Nasa’s Discovery shuttle has returned to earth after a successful mission to the International Space Station to transport crew and cargo to the station.

The space shuttle delivered two refrigerator-sized science experiment racks for research on materials and fluids, a sleeping compartment, an air purification system and a treadmill to the International Space Station.

The 14-day mission included three spacewalks to replace experiments outside the European Space Agency’s Columbus laboratory and an empty ammonia storage tank needed for moving excess heat from inside the station to the radiators outside.

The space shuttle also brought astronaut Tim Kopra back to earth after he was replaced by Nicole Stott.